If you've been trying to lose weight and suspect your body's working against you, you may be right, according to a University of Illinois study published in Obesity.
"When obese persons reduce their food intake too drastically, their bodies appear to resist their weight loss efforts. They may have to work harder and go slower in order to outsmart their brain chemistry," said Gregory G. Freund, a professor in the U of I College of Medicine and a member of U of I's Division of Nutritional Sciences.
He particularly cautions against beginning a diet with a fast or cleansing day, which appears to trigger significant alterations in the immune system that work against weight loss. "Take smaller steps to start your weight loss and keep it going," he said.
In the study, the scientist compared the effects of a short-term fast on two groups of mice. For 12 weeks, one group consumed a low-fat diet (10 percent fat); the other group was fed a high-fat (60 percent fat) and had become obese. The mice were then fasted for 24 hours. In that time, the leaner mice lost 18 percent of their body weight compared to 5 percent for the obese mice.
Freund said that there is an immune component to weight loss that has not been recognized. "Our data show that fasting induces an anti-inflammatory effect on a lean animal's neuroimmune system, and that effect is inhibited by a high-fat diet. Some of the brain-based chemical changes that occur in a lean animal simply don't occur in an obese animal," he said.
This breakdown occurs because obese animals resist downregulation of genes that activate the interleukin-1 (IL-1) system and associated anti-inflammatory cytokines, he said.
The scientist also studied differences in the behavior of the two groups of mice, monitoring how much they moved, administering tests to discern the animals' ability to learn and remember, and noting whether the mice exhibited signs of depression or anxiety.
The results suggest that beginning a diet with a fast or near-fast may alter brain chemistry in a way that adversely affects mood and motivation, undermining the person's weight-loss efforts.
"The obese mice simply didn't move as much as the other mice. Not only was there reduced locomotion generally, they didn't burrow in the way that mice normally do, and that's associated with depression and anxiety," he said.
Beginning a weight-loss program in a depressed frame of mind and with decreased motivation doesn't bode well for the diet's success, he noted.
Thursday, June 23, 2011
Monday, June 20, 2011
Fat substitutes linked to weight gain
Synthetic fat substitutes used in low-calorie potato chips and other foods could backfire and contribute to weight gain and obesity, according to a study published by the American Psychological Association.
The study, by researchers at Purdue University, challenges the conventional wisdom that foods made with fat substitutes help with weight loss. "Our research showed that fat substitutes can interfere with the body's ability to regulate food intake, which can lead to inefficient use of calories and weight gain," said Susan E. Swithers, PhD, the lead researcher and a Purdue psychology professor. The study was published online in the APA journal Behavioral Neuroscience.
The study used laboratory rats that were fed either a high-fat or low-fat diet of chow. Half of the rats in each group also were fed Pringles potato chips that are high in fat and calories. The remaining rats in each group were fed high-calorie Pringles chips on some days and low-calorie Pringles Light chips on other days. The Pringles Light chips are made with olestra, a synthetic fat substitute that has zero calories and passes through the body undigested.
For rats on the high-fat diet, the group that ate both types of potato chips consumed more food, gained more weight and developed more fatty tissue than the rats that ate only the high-calorie chips. The fat rats also didn't lose the extra weight even after the potato chips were removed from their diet. "Based on this data, a diet that is low in fat and calories might be a better strategy for weight loss than using fat substitutes," Swithers said. However, she warned that it can be difficult to extrapolate laboratory findings about rats to people, even though their biological responses to food are similar. The study was conducted by Swithers along with Purdue psychology professor Terry L. Davidson, PhD, and former Purdue undergraduate student Sean Ogden.
Why would a fat substitute confuse the body? Food with a sweet or fatty taste usually indicates a large number of calories, and the taste triggers various responses by the body, including salivation, hormonal secretions and metabolic reactions. Fat substitutes can interfere with that relationship when the body expects to receive a large burst of calories but is fooled by a fat substitute.
There is some good news if a diet is naturally low in fat. The rats that were fed a low-fat diet didn't experience significant weight gain from either type of potato chips. However, when those same rats were switched to a high-fat diet, the rats that had eaten both types of potato chips ate more food and gained more weight and body fat than the rats that had eaten only the high-calorie chips.
Swithers and Davidson have reported similar findings in previous rat studies that showed saccharin and other artificial sweeteners also can promote weight gain and increased body fat. The use of artificial sweeteners and fat substitutes has increased dramatically over the past 30 years, mirroring the increase in obesity in America. Dieters have turned to these artificial means to lower calories while still eating foods that taste sweet or fatty. So what is a dieter supposed to do to drop a size?
"Unfortunately, there is no silver bullet," Swithers said. "Eating food which is naturally low in fat and calories may be a better route than relying on fat substitutes or artificial sweeteners."
The study, by researchers at Purdue University, challenges the conventional wisdom that foods made with fat substitutes help with weight loss. "Our research showed that fat substitutes can interfere with the body's ability to regulate food intake, which can lead to inefficient use of calories and weight gain," said Susan E. Swithers, PhD, the lead researcher and a Purdue psychology professor. The study was published online in the APA journal Behavioral Neuroscience.
The study used laboratory rats that were fed either a high-fat or low-fat diet of chow. Half of the rats in each group also were fed Pringles potato chips that are high in fat and calories. The remaining rats in each group were fed high-calorie Pringles chips on some days and low-calorie Pringles Light chips on other days. The Pringles Light chips are made with olestra, a synthetic fat substitute that has zero calories and passes through the body undigested.
For rats on the high-fat diet, the group that ate both types of potato chips consumed more food, gained more weight and developed more fatty tissue than the rats that ate only the high-calorie chips. The fat rats also didn't lose the extra weight even after the potato chips were removed from their diet. "Based on this data, a diet that is low in fat and calories might be a better strategy for weight loss than using fat substitutes," Swithers said. However, she warned that it can be difficult to extrapolate laboratory findings about rats to people, even though their biological responses to food are similar. The study was conducted by Swithers along with Purdue psychology professor Terry L. Davidson, PhD, and former Purdue undergraduate student Sean Ogden.
Why would a fat substitute confuse the body? Food with a sweet or fatty taste usually indicates a large number of calories, and the taste triggers various responses by the body, including salivation, hormonal secretions and metabolic reactions. Fat substitutes can interfere with that relationship when the body expects to receive a large burst of calories but is fooled by a fat substitute.
There is some good news if a diet is naturally low in fat. The rats that were fed a low-fat diet didn't experience significant weight gain from either type of potato chips. However, when those same rats were switched to a high-fat diet, the rats that had eaten both types of potato chips ate more food and gained more weight and body fat than the rats that had eaten only the high-calorie chips.
Swithers and Davidson have reported similar findings in previous rat studies that showed saccharin and other artificial sweeteners also can promote weight gain and increased body fat. The use of artificial sweeteners and fat substitutes has increased dramatically over the past 30 years, mirroring the increase in obesity in America. Dieters have turned to these artificial means to lower calories while still eating foods that taste sweet or fatty. So what is a dieter supposed to do to drop a size?
"Unfortunately, there is no silver bullet," Swithers said. "Eating food which is naturally low in fat and calories may be a better route than relying on fat substitutes or artificial sweeteners."
Wednesday, June 15, 2011
Magical thinking helps dieters cope with unrealistic expectations
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Magical thinking, usually dismissed as naïve and irrational, can actually help consumers cope with stressful situations like trying to lose weight, according to a new study in the Journal of Consumer Research.
"Magical thinking occurs when an individual invokes mystical, supernatural forces to understand, predict, or even influence events to overcome these stressful situations," write authors Yannik St. James (HEC Montreal), Jay M. Handelman, and Shirley F. Taylor (both Queen's University, Kingston, Canada).
"Weight loss activities are stressful for a number of reasons: being overweight is associated with several negative health consequences as well as considerable social stigma," the authors write. "Consumers are expected to conform to unrealistic cultural ideals of slenderness and they are simultaneously enticed to indulge in abundant, highly caloric, processed food."
To cope with these conflicting pressures and expectations, consumers engage in various forms of magical thinking. They describe weight loss as being influenced by mysterious forces, such as a body that "conspires" against them or food that "seduces" them. They also hope that good deeds will be rewarded (like eating chips without consequences after eating cabbage soup all day) and resort to "magical solutions" like fad diets. Finally, they try to fool the scale by changing to lighter clothing or exercising before being weighed.
These magical thinkers are not misinformed, the authors emphasize. "By invoking and negotiating with mystical forces, consumers actively work to create uncertainty and ambiguity as a way to generate hope and possibility in a cultural domain where they otherwise experience very little," the authors write.
The authors believe their findings should be of interest to consumer advocates and policy makers. "Programs directed at correcting fallacious consumer knowledge and enjoining consumers to exert greater self-control might be of limited value," the authors write. "Indeed, these approaches eliminate certain consumer coping strategies without affecting the source of stress—the cultural expectation to be thin in a culture that entices consumers with endless unhealthy food and lifestyle alternatives."
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Magical thinking, usually dismissed as naïve and irrational, can actually help consumers cope with stressful situations like trying to lose weight, according to a new study in the Journal of Consumer Research.
"Magical thinking occurs when an individual invokes mystical, supernatural forces to understand, predict, or even influence events to overcome these stressful situations," write authors Yannik St. James (HEC Montreal), Jay M. Handelman, and Shirley F. Taylor (both Queen's University, Kingston, Canada).
"Weight loss activities are stressful for a number of reasons: being overweight is associated with several negative health consequences as well as considerable social stigma," the authors write. "Consumers are expected to conform to unrealistic cultural ideals of slenderness and they are simultaneously enticed to indulge in abundant, highly caloric, processed food."
To cope with these conflicting pressures and expectations, consumers engage in various forms of magical thinking. They describe weight loss as being influenced by mysterious forces, such as a body that "conspires" against them or food that "seduces" them. They also hope that good deeds will be rewarded (like eating chips without consequences after eating cabbage soup all day) and resort to "magical solutions" like fad diets. Finally, they try to fool the scale by changing to lighter clothing or exercising before being weighed.
These magical thinkers are not misinformed, the authors emphasize. "By invoking and negotiating with mystical forces, consumers actively work to create uncertainty and ambiguity as a way to generate hope and possibility in a cultural domain where they otherwise experience very little," the authors write.
The authors believe their findings should be of interest to consumer advocates and policy makers. "Programs directed at correcting fallacious consumer knowledge and enjoining consumers to exert greater self-control might be of limited value," the authors write. "Indeed, these approaches eliminate certain consumer coping strategies without affecting the source of stress—the cultural expectation to be thin in a culture that entices consumers with endless unhealthy food and lifestyle alternatives."
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Monday, June 13, 2011
Sleepiness may impair the brain's inhibitory control when viewing high-calorie foods
Study suggests that daytime sleepiness may affect eating behavior by influencing the brain's response to food
Daytime sleepiness may affect inhibitory control in the brain when viewing tantalizing, high-calorie foods, suggests a research abstract.
Results show that greater daytime sleepiness was associated with decreased activation in the prefrontal cortex during visual presentations of enticing, high-calorie food images. The prefrontal cortex is a brain region that plays an important role in inhibitory processing.
"Self-reported daytime sleepiness among healthy, normally rested individuals correlated with reduced responsiveness of inhibitory brain regions when confronted with images of highly appetizing foods," said principal investigator William Killgore, PhD, assistant professor of psychology at Harvard Medical School and McLean Hospital in Belmont, Mass. "It suggests that even normal fluctuations in sleepiness may be capable of altering brain responses that are important for regulating dietary intake, potentially affecting the types of choices that individuals make when selecting whether and what to eat."
The research team of Killgore, lead author Melissa Weiner, and Zachary Schwab studied 12 healthy men and women between the ages of 19 and 45 years. The participants underwent functional magnetic resonance imaging (fMRI) while viewing pictures of high-calorie foods, low-calorie foods, and control images of plants and rocks. Subjective, self-reported daytime sleepiness was measured with the Epworth Sleepiness Scale, which evaluates how likely an individual is to doze off or fall asleep during certain situations such as while sitting and reading or watching TV.
According to the authors, prior evidence suggests that healthy adults activate inhibitory regions of the prefrontal cortex in response to high-calorie food images. However, insufficient sleep is often associated with reduced metabolic activity within these same prefrontal regions.
Killgore noted that the rapidly rising rate of obesity makes it important to understand the relationship between sleep-related factors, brain responses to food, and eating behavior.
"Given the chronic level of sleep restriction in our society, such relationships could have epidemiologic implications regarding the current increase in obesity in westernized countries," he said.
In a previous study published in Neuroreport in 2010, Killgore also found sex differences in cerebral responses to the caloric content of food images. Results of that study indicate that when viewing high-calorie food images, women showed significantly greater activation than men in brain regions that are involved in behavioral control and self-referential cognition.
Tuesday, June 7, 2011
Obesity is a risk factor for Alzheimer's disease
But weight loss due to bariatric surgery may reduce the risk of this common dementia
Obesity is a risk factor for Alzheimer's disease, but weight loss due to bariatric surgery may reduce the risk of this common dementia, a new study suggests. The results will be presented Sunday at The Endocrine Society's 93rd Annual Meeting in Boston.
"Our study shows for the first time that weight loss resulting from bariatric surgery leads to a reduction in the expression of genes related to Alzheimer's disease," said the study's main author, Paresh Dandona, MD, PhD, professor at State University of New York (SUNY) at Buffalo.
Past research has shown that obesity and Type 2 diabetes increase the chance of getting Alzheimer's disease. In this study, 15 morbidly obese patients with Type 2 diabetes had Roux-en-Y gastric bypass surgery and lost nearly 86 pounds, on average, over six months. The patients gave blood samples before surgery and six months later.
Dandona and co-workers recently found that white blood cells in the circulatjavascript:void(0)ing blood, called peripheral blood mononuclear cells, express amyloid precursor protein. This APP is the precursor of beta-amyloid, protein pieces that form plaques in the brain, one of the key brain abnormalities in Alzheimer's disease.
In this study, the researchers measured the expression of APP, and it fell by 22 percent after weight loss. Expression of the messenger RNA that carries genetic information for APP decreased by an average of 31 percent, the data showed.
After weight loss there also was reduced expression in other genes related to risk of Alzheimer's disease, according to the authors. They included the presenilin-2 gene, which mediates the conversion of APP into beta-amyloid. Also reduced in expression was the gene for an enzyme known as glycogen synthase kinase-3-beta (GSK-3-beta), which phosphorylates, or abnormally modifies, tau protein to form the neurofibrillary tangles in the brains of people with Alzheimer's disease. Tangles are a main suspect in the death of nerve cells in this disease.
Dandona said that their clinical study cannot prove that these effects are also occurring in the brain. If it is true, he said, "this may have implications for the treatment of Alzheimer's disease."
"It is relevant that cognitive function has previously been shown to improve with weight loss following bariatric surgery," Dandona said.
Also, inflammation is another brain abnormality seen in Alzheimer's disease, and in this study, the gene expression changes paralleled the reductions in the blood of mediators of inflammation, he said.
Obesity is a risk factor for Alzheimer's disease, but weight loss due to bariatric surgery may reduce the risk of this common dementia, a new study suggests. The results will be presented Sunday at The Endocrine Society's 93rd Annual Meeting in Boston.
"Our study shows for the first time that weight loss resulting from bariatric surgery leads to a reduction in the expression of genes related to Alzheimer's disease," said the study's main author, Paresh Dandona, MD, PhD, professor at State University of New York (SUNY) at Buffalo.
Past research has shown that obesity and Type 2 diabetes increase the chance of getting Alzheimer's disease. In this study, 15 morbidly obese patients with Type 2 diabetes had Roux-en-Y gastric bypass surgery and lost nearly 86 pounds, on average, over six months. The patients gave blood samples before surgery and six months later.
Dandona and co-workers recently found that white blood cells in the circulatjavascript:void(0)ing blood, called peripheral blood mononuclear cells, express amyloid precursor protein. This APP is the precursor of beta-amyloid, protein pieces that form plaques in the brain, one of the key brain abnormalities in Alzheimer's disease.
In this study, the researchers measured the expression of APP, and it fell by 22 percent after weight loss. Expression of the messenger RNA that carries genetic information for APP decreased by an average of 31 percent, the data showed.
After weight loss there also was reduced expression in other genes related to risk of Alzheimer's disease, according to the authors. They included the presenilin-2 gene, which mediates the conversion of APP into beta-amyloid. Also reduced in expression was the gene for an enzyme known as glycogen synthase kinase-3-beta (GSK-3-beta), which phosphorylates, or abnormally modifies, tau protein to form the neurofibrillary tangles in the brains of people with Alzheimer's disease. Tangles are a main suspect in the death of nerve cells in this disease.
Dandona said that their clinical study cannot prove that these effects are also occurring in the brain. If it is true, he said, "this may have implications for the treatment of Alzheimer's disease."
"It is relevant that cognitive function has previously been shown to improve with weight loss following bariatric surgery," Dandona said.
Also, inflammation is another brain abnormality seen in Alzheimer's disease, and in this study, the gene expression changes paralleled the reductions in the blood of mediators of inflammation, he said.
Cut down on 'carbs' to reduce body fat
A modest reduction in consumption of carbohydrate foods may promote loss of deep belly fat, even with little or no change in weight, a new study finds. Presentation of the study results will be Sunday at The Endocrine Society's 93rd Annual Meeting in Boston.
When paired with weight loss, consumption of a moderately reduced carbohydrate diet can help achieve a reduction of total body fat, according to principal author Barbara Gower, PhD, a professor of nutrition sciences at the University of Alabama at Birmingham.
"These changes could help reduce the risk of developing Type 2 diabetes, stroke and coronary artery disease," Gower said, noting that excess visceral, or intra-abdominal, fat raises the risk of these diseases.
Gower and her colleagues conducted the study, with funding from the National Institutes of Health, in 69 overweight but healthy men and women. Subjects received food for two consecutive eight-week periods: first a weight maintenance intervention, and then a weight loss intervention, which cut the number of calories that each person ate by 1,000 each day.
Subjects received either a standard lower-fat diet or a diet with a modest reduction in carbohydrates, or "carbs," but slightly higher in fat than the standard diet. The moderately carb-restricted diet contained foods that had a relatively low glycemic index, a measure of the extent to which the food raises blood glucose levels. This diet consisted of 43 percent calories from carbohydrates and 39 percent calories from fat, whereas the standard diet contained 55 percent of calories from carbohydrates and 27 percent from fat. Protein made up the other 18 percent of each diet.
At the beginning and end of each study phase, the researchers measured the subjects' fat deep inside the abdomen and their total body fat using computed tomography (CT) and dual-energy x-ray absorptiometry (DXA) scans.
After the weight maintenance phase, subjects who consumed the moderately carb-restricted diet had 11 percent less deep abdominal fat than those who ate the standard diet. However, when the researchers analyzed results by race, they found it was exclusive to whites. Whites have more deep abdominal fat than Blacks even when matched for body weight or percent body fat, and may benefit from loss of this metabolically harmful depot, Gower said.
During the weight loss phase, subjects on both diets lost weight. However, the moderately carb-restricted diet promoted a 4 percent greater loss of total body fat, Gower said. "For individuals willing to go on a weight-loss diet, a modest reduction in carbohydrate-containing foods may help them preferentially lose fat, rather than lean tissue," she said. "The moderately reduced carbohydrate diet allows a variety of foods to meet personal preferences."
When paired with weight loss, consumption of a moderately reduced carbohydrate diet can help achieve a reduction of total body fat, according to principal author Barbara Gower, PhD, a professor of nutrition sciences at the University of Alabama at Birmingham.
"These changes could help reduce the risk of developing Type 2 diabetes, stroke and coronary artery disease," Gower said, noting that excess visceral, or intra-abdominal, fat raises the risk of these diseases.
Gower and her colleagues conducted the study, with funding from the National Institutes of Health, in 69 overweight but healthy men and women. Subjects received food for two consecutive eight-week periods: first a weight maintenance intervention, and then a weight loss intervention, which cut the number of calories that each person ate by 1,000 each day.
Subjects received either a standard lower-fat diet or a diet with a modest reduction in carbohydrates, or "carbs," but slightly higher in fat than the standard diet. The moderately carb-restricted diet contained foods that had a relatively low glycemic index, a measure of the extent to which the food raises blood glucose levels. This diet consisted of 43 percent calories from carbohydrates and 39 percent calories from fat, whereas the standard diet contained 55 percent of calories from carbohydrates and 27 percent from fat. Protein made up the other 18 percent of each diet.
At the beginning and end of each study phase, the researchers measured the subjects' fat deep inside the abdomen and their total body fat using computed tomography (CT) and dual-energy x-ray absorptiometry (DXA) scans.
After the weight maintenance phase, subjects who consumed the moderately carb-restricted diet had 11 percent less deep abdominal fat than those who ate the standard diet. However, when the researchers analyzed results by race, they found it was exclusive to whites. Whites have more deep abdominal fat than Blacks even when matched for body weight or percent body fat, and may benefit from loss of this metabolically harmful depot, Gower said.
During the weight loss phase, subjects on both diets lost weight. However, the moderately carb-restricted diet promoted a 4 percent greater loss of total body fat, Gower said. "For individuals willing to go on a weight-loss diet, a modest reduction in carbohydrate-containing foods may help them preferentially lose fat, rather than lean tissue," she said. "The moderately reduced carbohydrate diet allows a variety of foods to meet personal preferences."
The DASH Diet Predicts Weight Gain
Adherence to dietary pattern associated with lower BMI in adolescent girls
Adolescent girls whose diet resembles one recommended for adults with hypertension appear to have smaller gains in overall body mass index (BMI) over 10 years, according to a report in the June issue of Archives of Pediatrics & Adolescent Medicine, one of the JAMA/Archives journals.
"Excess weight during childhood leads to numerous health problems and is even associated with premature death as an adult," the authors write as background information in the article. However, the authors note that examinations of food-based dietary patterns acknowledge that consuming various nutrients together can have positive influences on health. One such diet pattern, the Dietary Approach to Stop Hypertension (DASH), was originally studied as a treatment for adults with hypertension, according to background in the article.
Jonathan P. B. Berz, M.D., M.Sc., of Boston University Medical Center, and colleagues evaluated the effects of a DASH-style eating plan on BMI (calculated as weight in kilograms divided by height in meters squared) in a racially diverse sample of adolescent girls. The authors examined data from 2,237 girls 9 years of age who participated in the National Growth and Health Study from 1987-1988 and were followed up for 10 years. Data were gathered annually and each participant was given a DASH food group score based on individual adherence to dietary requirements.
Higher DASH scores were associated with higher total energy intake, as well as higher average intake from each food group (whole grains, vegetables, fruits, lean meats, low-fat dairy and nuts/seeds/legumes). Girls in the highest quintile of DASH scores had the smallest gains in BMI during the study, and had the lowest BMIs at the end of follow-up. Conversely, at age 19 years, girls in the lowest DASH score quintile had an average BMI that was greater than the threshold for overweight as defined by the 85th percentile for age.
"In particular, higher consumption of fruits, whole grains and low-fat dairy products led to less weight gain," the authors noted. Participants who consumed two or more servings of fruit per day had the smallest gains in BMI during the study years and had the lowest BMI at the end of follow-up. Compared with participants consuming the least amount of whole grains, those who consumed the most had lower BMI scores over time and a lower BMI at the end of follow-up. The same results were seen for girls consuming higher amounts of low-fat dairy products.
"We found that higher adherence to a DASH-style diet resulted in a consistently lower BMI between the ages of 9 and 19 years," the authors conclude. "Such an eating pattern may help prevent excess weight gain during adolescence."
Arch Pediatr Adolesc Med. 2011;165[6]:540-546
Editorial: The DASH Diet Predicts Weight Gain
In an accompanying editorial, Robert C. Klesges, Ph.D. and Marion Hare, M.D., of the University of Tennessee Health Science Center, Memphis, Tenn., comment on the findings of this study. "As Berz et al point out, the DASH diet has been well validated in adults, and there is absolutely no reason for it to not work in children," they write. "The DASH diet is flexible and should meet the food preferences of most children. However, interventions for children need to be simplified; therefore, it make sense to specifically recommend increased consumption of fruits and low-fat dairy products."
"In summary, Berz et al add to a growing body of literature that will eventually help us to understand and hopefully treat pediatric obesity. A logical step in this literature is to test the DASH diet in children along with other efficacious adult obesity interventions."
Arch Pediatr Adolesc Med. 2011;165[6]:567-568.
Adolescent girls whose diet resembles one recommended for adults with hypertension appear to have smaller gains in overall body mass index (BMI) over 10 years, according to a report in the June issue of Archives of Pediatrics & Adolescent Medicine, one of the JAMA/Archives journals.
"Excess weight during childhood leads to numerous health problems and is even associated with premature death as an adult," the authors write as background information in the article. However, the authors note that examinations of food-based dietary patterns acknowledge that consuming various nutrients together can have positive influences on health. One such diet pattern, the Dietary Approach to Stop Hypertension (DASH), was originally studied as a treatment for adults with hypertension, according to background in the article.
Jonathan P. B. Berz, M.D., M.Sc., of Boston University Medical Center, and colleagues evaluated the effects of a DASH-style eating plan on BMI (calculated as weight in kilograms divided by height in meters squared) in a racially diverse sample of adolescent girls. The authors examined data from 2,237 girls 9 years of age who participated in the National Growth and Health Study from 1987-1988 and were followed up for 10 years. Data were gathered annually and each participant was given a DASH food group score based on individual adherence to dietary requirements.
Higher DASH scores were associated with higher total energy intake, as well as higher average intake from each food group (whole grains, vegetables, fruits, lean meats, low-fat dairy and nuts/seeds/legumes). Girls in the highest quintile of DASH scores had the smallest gains in BMI during the study, and had the lowest BMIs at the end of follow-up. Conversely, at age 19 years, girls in the lowest DASH score quintile had an average BMI that was greater than the threshold for overweight as defined by the 85th percentile for age.
"In particular, higher consumption of fruits, whole grains and low-fat dairy products led to less weight gain," the authors noted. Participants who consumed two or more servings of fruit per day had the smallest gains in BMI during the study years and had the lowest BMI at the end of follow-up. Compared with participants consuming the least amount of whole grains, those who consumed the most had lower BMI scores over time and a lower BMI at the end of follow-up. The same results were seen for girls consuming higher amounts of low-fat dairy products.
"We found that higher adherence to a DASH-style diet resulted in a consistently lower BMI between the ages of 9 and 19 years," the authors conclude. "Such an eating pattern may help prevent excess weight gain during adolescence."
Arch Pediatr Adolesc Med. 2011;165[6]:540-546
Editorial: The DASH Diet Predicts Weight Gain
In an accompanying editorial, Robert C. Klesges, Ph.D. and Marion Hare, M.D., of the University of Tennessee Health Science Center, Memphis, Tenn., comment on the findings of this study. "As Berz et al point out, the DASH diet has been well validated in adults, and there is absolutely no reason for it to not work in children," they write. "The DASH diet is flexible and should meet the food preferences of most children. However, interventions for children need to be simplified; therefore, it make sense to specifically recommend increased consumption of fruits and low-fat dairy products."
"In summary, Berz et al add to a growing body of literature that will eventually help us to understand and hopefully treat pediatric obesity. A logical step in this literature is to test the DASH diet in children along with other efficacious adult obesity interventions."
Arch Pediatr Adolesc Med. 2011;165[6]:567-568.
Surgically shrinking the stomach when conservative weight-loss treatments fail
The treatment of obesity still needs improvement. In the current issue of Deutsches Ärzteblatt International, Norbert Runkel and colleagues present a new, interdisciplinary S3 guideline entitled "Bariatric Surgery" (Dtsch Arztebl Int 2011; 108[20]: 341).
One in two persons in Germany is overweight, and every fifth one is obese. Conservative treatment is considered to have been exhausted when it fails to bring about a 10% to 20% loss of weight in one year in a patient whose initial body-mass index was between 35 and 40 kg/m2.
In this situation, bariatric surgery is much more effective than conservative treatment for lowering weight and reducing the frequency of other medical problems due to obesity. The goal of surgery is to make the stomach smaller or shorten the passage of food through the gastrointestinal tract, so that the body takes up a smaller amount of nutrients. The currently established types of bariatric surgery in Germany are gastric banding, gastric bypass, sleeve gastrectomy, and biliopancreatic diversion. In the new guideline, the authors discuss the choice of the operative procedure, surgical complications, and postoperative care.
The guideline was produced according to the method specified by the Association of Scientific Medical Societies in Germany (Arbeitsgemeinschaft der Wissenschaftlich-medizinischen Fachgesellschaften, AWMF). Its evidence-based recommendations are intended to aid in the further development of bariatric surgery in Germany along with the necessary quality assurance.
One in two persons in Germany is overweight, and every fifth one is obese. Conservative treatment is considered to have been exhausted when it fails to bring about a 10% to 20% loss of weight in one year in a patient whose initial body-mass index was between 35 and 40 kg/m2.
In this situation, bariatric surgery is much more effective than conservative treatment for lowering weight and reducing the frequency of other medical problems due to obesity. The goal of surgery is to make the stomach smaller or shorten the passage of food through the gastrointestinal tract, so that the body takes up a smaller amount of nutrients. The currently established types of bariatric surgery in Germany are gastric banding, gastric bypass, sleeve gastrectomy, and biliopancreatic diversion. In the new guideline, the authors discuss the choice of the operative procedure, surgical complications, and postoperative care.
The guideline was produced according to the method specified by the Association of Scientific Medical Societies in Germany (Arbeitsgemeinschaft der Wissenschaftlich-medizinischen Fachgesellschaften, AWMF). Its evidence-based recommendations are intended to aid in the further development of bariatric surgery in Germany along with the necessary quality assurance.
Yo-yo dieting appears to be healthier than lifelong obesity
A new study comparing lifelong obesity with the weight fluctuations of "yo-yo dieting" suggests it is better to attempt to lose weight despite repeated failures at keeping the weight off than to not diet and remain obese. The results will be presented Monday at The Endocrine Society's 93rd Annual Meeting in Boston.
"It is clear that remaining on a stable, healthy diet provides the best outcome for health and longevity," said the study's principal investigator, Edward List, PhD, a scientist at Ohio University, Athens. "However, obese individuals commonly weight cycle—they have repeated intentional weight loss followed by weight regain, often called yo-yo dieting. While yo-yo dieting is thought to be harmful, there is little hard scientific evidence to support that."
To determine the long-term health effects of yo-yo dieting, List and his collaborators performed what they call "the first controlled study of a yo-yo diet regimen used for an entire life span." Because of the challenges of performing a long-term controlled feeding study in humans, they used mice to test whether weight fluctuation due to yo-yo dieting is as unhealthy as lifelong obesity.
Thirty mice, in groups of 10 each, received one of three diets: high fat, low fat or a yo-yo diet, consisting of four weeks of the high-fat diet followed by four weeks of the low-fat diet. The mice stayed on their respective diets throughout their life span. Measures of health, including body weight, body fat and blood glucose (sugar) levels, were obtained.
List said the yo-yo diet resulted in large fluctuations in these health measures, decreasing during the low-fat diet and increasing to a diabetic state during the high-fat diet. When health measures during the high-fat and low-fat diet regimens of the yo-yo diet group were averaged, their "average health" was improved compared with obese mice that stayed on the high-fat diet, he reported. Compared with the mice fed the high-fat diet, mice on the yo-yo diet lived nearly 35 percent longer.
"Surprisingly, the mice on the yo-yo diet had a similar life span to that of the low-fat-fed group," List said.
These findings are important in light of the growing epidemic of obesity around the world, he stated.
"The fear of negative health consequences due to weight cycling may be overemphasized," List concluded. "From our study, it appears that it is better to continue to encourage weight loss regardless of the number of attempts and failures."
"It is clear that remaining on a stable, healthy diet provides the best outcome for health and longevity," said the study's principal investigator, Edward List, PhD, a scientist at Ohio University, Athens. "However, obese individuals commonly weight cycle—they have repeated intentional weight loss followed by weight regain, often called yo-yo dieting. While yo-yo dieting is thought to be harmful, there is little hard scientific evidence to support that."
To determine the long-term health effects of yo-yo dieting, List and his collaborators performed what they call "the first controlled study of a yo-yo diet regimen used for an entire life span." Because of the challenges of performing a long-term controlled feeding study in humans, they used mice to test whether weight fluctuation due to yo-yo dieting is as unhealthy as lifelong obesity.
Thirty mice, in groups of 10 each, received one of three diets: high fat, low fat or a yo-yo diet, consisting of four weeks of the high-fat diet followed by four weeks of the low-fat diet. The mice stayed on their respective diets throughout their life span. Measures of health, including body weight, body fat and blood glucose (sugar) levels, were obtained.
List said the yo-yo diet resulted in large fluctuations in these health measures, decreasing during the low-fat diet and increasing to a diabetic state during the high-fat diet. When health measures during the high-fat and low-fat diet regimens of the yo-yo diet group were averaged, their "average health" was improved compared with obese mice that stayed on the high-fat diet, he reported. Compared with the mice fed the high-fat diet, mice on the yo-yo diet lived nearly 35 percent longer.
"Surprisingly, the mice on the yo-yo diet had a similar life span to that of the low-fat-fed group," List said.
These findings are important in light of the growing epidemic of obesity around the world, he stated.
"The fear of negative health consequences due to weight cycling may be overemphasized," List concluded. "From our study, it appears that it is better to continue to encourage weight loss regardless of the number of attempts and failures."
Desserts With a Low Glycemic Index May Benefit Weight-Loss Efforts
Overweight girls lose more weight and can better stay on a healthy diet if they eat sugar-free, low-fat desserts several times weekly, as opposed to any dessert once a week, a new study finds.
"Dieters commonly splurge on dessert once a week, usually choosing fattening items," said lead investigator Antonia Dastamani, MD, PhD, a pediatrician and research fellow at Athens University School of Medicine in Athens, Greece. "However, we found a positive effect of more frequent consumption of desserts that have a low glycemic index and low glycemic load."
Carbohydrates have a low glycemic index (GI) if they raise glucose, or blood sugar, levels more slowly than other carbohydrates do. The glycemic load (GL), which depends on serving size, is the food's total effect on blood sugar.
"Studies suggest that low GI/GL diets have a positive effect on weight control and improving insulin resistance," Dastamani said.
Obesity can cause insulin resistance, in which the body does not properly use the hormone insulin. This results in high blood sugar levels and sets the stage for development of diabetes.
Dastamani and her colleagues tested the effects of incorporating into a balanced diet certain low-calorie, low-GI/GL desserts containing sugar substitutes such as sucralose. The products are made by the Giotis Company, a food production company in Athens, which donated the desserts and helped fund the study.
The investigators studied the effects of two diets in 29 girls, ages 10 to 14 years, who had a body mass index (BMI) in the 85th percentile or above, considered overweight or obese. A group of 15 girls ate a diet consisting of 45 percent carbohydrates, 35 percent fats and 20 percent proteins, including the low-GI/GL desserts four times a week. The other group of 14 girls followed the same diet except, instead of the low-GI/GL desserts, they ate desserts of their choice once a week.
After three months on the diet, both groups improved their BMI (body composition). Compared with the second group, however, the group that ate the low-GI/GL desserts lost significantly more weight and had better average BMI and systolic blood pressure (the first number in a blood pressure reading), the authors reported.
Girls who ate the low-GI/GL desserts also had significantly improved levels of the appetite-suppressing hormone leptin, the researchers found. They also had better improvements in biochemical markers of insulin resistance (fasting insulin levels in the blood and the homeostatic model assessment, or HOMA, index).
"Childhood obesity is pandemic, and dietary changes among overweight and obese children must be a priority," Dastamani said. "Desserts with a low glycemic index and glycemic load, when eaten in moderation, are valuable tools in the treatment of pediatric obesity."
"Dieters commonly splurge on dessert once a week, usually choosing fattening items," said lead investigator Antonia Dastamani, MD, PhD, a pediatrician and research fellow at Athens University School of Medicine in Athens, Greece. "However, we found a positive effect of more frequent consumption of desserts that have a low glycemic index and low glycemic load."
Carbohydrates have a low glycemic index (GI) if they raise glucose, or blood sugar, levels more slowly than other carbohydrates do. The glycemic load (GL), which depends on serving size, is the food's total effect on blood sugar.
"Studies suggest that low GI/GL diets have a positive effect on weight control and improving insulin resistance," Dastamani said.
Obesity can cause insulin resistance, in which the body does not properly use the hormone insulin. This results in high blood sugar levels and sets the stage for development of diabetes.
Dastamani and her colleagues tested the effects of incorporating into a balanced diet certain low-calorie, low-GI/GL desserts containing sugar substitutes such as sucralose. The products are made by the Giotis Company, a food production company in Athens, which donated the desserts and helped fund the study.
The investigators studied the effects of two diets in 29 girls, ages 10 to 14 years, who had a body mass index (BMI) in the 85th percentile or above, considered overweight or obese. A group of 15 girls ate a diet consisting of 45 percent carbohydrates, 35 percent fats and 20 percent proteins, including the low-GI/GL desserts four times a week. The other group of 14 girls followed the same diet except, instead of the low-GI/GL desserts, they ate desserts of their choice once a week.
After three months on the diet, both groups improved their BMI (body composition). Compared with the second group, however, the group that ate the low-GI/GL desserts lost significantly more weight and had better average BMI and systolic blood pressure (the first number in a blood pressure reading), the authors reported.
Girls who ate the low-GI/GL desserts also had significantly improved levels of the appetite-suppressing hormone leptin, the researchers found. They also had better improvements in biochemical markers of insulin resistance (fasting insulin levels in the blood and the homeostatic model assessment, or HOMA, index).
"Childhood obesity is pandemic, and dietary changes among overweight and obese children must be a priority," Dastamani said. "Desserts with a low glycemic index and glycemic load, when eaten in moderation, are valuable tools in the treatment of pediatric obesity."
Monday, June 6, 2011
Obesity Raises Breast Cancer Survivors' Risk of Dying of the Cancer
Women with a healthy body weight before and after diagnosis of breast cancer are more likely to survive the disease long term, a new study finds.
The study, conducted in nearly 4,000 breast cancer survivors, found that obesity is strongly linked to death due to breast cancer. In particular, overweight or obese women with a history of estrogen receptor-positive breast cancer, but not those with estrogen receptor-negative cancer, had a higher risk of dying of their disease, said the study's lead author, Christina Dieli-Conwright, PhD.
"This relationship between dying and being obese or overweight may depend on whether the type of breast cancer is hormonally dependent," said Dieli-Conwright, assistant research professor at City of Hope National Medical Center in Duarte, Calif.
The research involved participants of the large California Teachers Study who, between 1995 and 2006, received a diagnosis of invasive breast cancer -- cancer that has spread beyond the breast ducts. Of the 3,995 women studied, 262 died of breast cancer through 2007, the authors reported in their abstract.
They defined obesity as a body mass index (BMI, in kg/m2) of 30 or higher. The authors obtained BMI, a measure of height and weight, from questionnaires showing each participant's self-reported height and weight at baseline and at age 18. Baseline was the beginning of the study and was near, but necessarily at, diagnosis, according to Dieli-Conwright.
Women who were obese at baseline had a 69 percent higher risk of dying of their breast cancer than did nonobese women, Dieli-Conwright said. This same increased mortality, or death, risk was present in women who were overweight (BMI of 25 to 29) at age 18.
The researchers also analyzed the mortality risk by estrogen receptor status (whether the hormone estrogen fuels the breast cancer). They found that the higher the BMI, the greater the risk of dying of breast cancer for women with estrogen-dependent cancer. They saw no such link in women with estrogen-negative breast cancer. Women who are obese or overweight tend to have higher levels of circulating estrogen, which likely explains this difference, Dieli-Conwright said.
Their findings add to the growing scientific evidence that obesity raises the risk of both developing breast cancer and dying of it.
"What we know now is that there is a strong link between dying from breast cancer and being obese," Dieli-Conwright said. "And it's not just your BMI near the time you're diagnosed that's important."
She continued, "With the obesity epidemic on the rise, weight management programs using exercise and diet are vital in cancer prevention and survivorship."
The study, conducted in nearly 4,000 breast cancer survivors, found that obesity is strongly linked to death due to breast cancer. In particular, overweight or obese women with a history of estrogen receptor-positive breast cancer, but not those with estrogen receptor-negative cancer, had a higher risk of dying of their disease, said the study's lead author, Christina Dieli-Conwright, PhD.
"This relationship between dying and being obese or overweight may depend on whether the type of breast cancer is hormonally dependent," said Dieli-Conwright, assistant research professor at City of Hope National Medical Center in Duarte, Calif.
The research involved participants of the large California Teachers Study who, between 1995 and 2006, received a diagnosis of invasive breast cancer -- cancer that has spread beyond the breast ducts. Of the 3,995 women studied, 262 died of breast cancer through 2007, the authors reported in their abstract.
They defined obesity as a body mass index (BMI, in kg/m2) of 30 or higher. The authors obtained BMI, a measure of height and weight, from questionnaires showing each participant's self-reported height and weight at baseline and at age 18. Baseline was the beginning of the study and was near, but necessarily at, diagnosis, according to Dieli-Conwright.
Women who were obese at baseline had a 69 percent higher risk of dying of their breast cancer than did nonobese women, Dieli-Conwright said. This same increased mortality, or death, risk was present in women who were overweight (BMI of 25 to 29) at age 18.
The researchers also analyzed the mortality risk by estrogen receptor status (whether the hormone estrogen fuels the breast cancer). They found that the higher the BMI, the greater the risk of dying of breast cancer for women with estrogen-dependent cancer. They saw no such link in women with estrogen-negative breast cancer. Women who are obese or overweight tend to have higher levels of circulating estrogen, which likely explains this difference, Dieli-Conwright said.
Their findings add to the growing scientific evidence that obesity raises the risk of both developing breast cancer and dying of it.
"What we know now is that there is a strong link between dying from breast cancer and being obese," Dieli-Conwright said. "And it's not just your BMI near the time you're diagnosed that's important."
She continued, "With the obesity epidemic on the rise, weight management programs using exercise and diet are vital in cancer prevention and survivorship."
Friday, June 3, 2011
Weight loss success in a 3-D virtual world
Participants in two weight-loss programs -- one involving traditional health club sessions and the other delivered online in a 3D virtual world -- lost similar amounts of weight and body fat, but the online contingent reported significantly greater gains in behaviors that could help them live healthier and leaner lives.
"It's counter-intuitive, the idea of being more active in a virtual world, but the activities that they do in a virtual world can carry over into the real world," said Jeanne Johnston, assistant professor of kinesiology at Indiana University. "Through visualization and education, they can try activities that they had not tried before."
More and more people have been turning to online weight-loss programs, but Johnston said the programs often lack important elements of human interaction. The IU researchers wanted to travel even farther into cyber space by evaluating a weight-loss program offered in a virtual-reality environment, where visitors use avatars to interact with others or the computer-simulated environment -- in this case, a simulated fitness club.
"The virtual world program was at least as beneficial as the face-to-face program and in some ways, more effective," Johnston said. "It has the potential to reach people who normally wouldn't go to a gym or join a program because of limitations, such as time or discomfort with a fitness center environment."
The findings in the study "Comparison of a Face-to-Face versus Virtual World Weight Loss Program" will be discussed on Friday at the American College of Sports Medicine annual meeting in Denver. They will be presented during a poster presentation in Hall B from 8-9:30 a.m. MDT.
For 12 weeks, members of the each weight-loss program spent at least four hours a week attending meetings at a virtual or real club. In both they learned about nutrition, physical activity, changing habits and how to benefit from social supports. The study involved overweight and obese people -- mostly women. The average age of the face-to-face group was 37. The average age of the virtual world group, which provided training in how to use the Web-based platform Second Life, http://secondlife.com/, was 46.
The participants in each group lost a comparable amount of weight -- on average almost 10 pounds -- and saw similar decreases in body mass index and body fat. The big differences between the two groups involved behaviors. Participants in the face-to-face group reported no significant changes in any of the behaviors evaluated -- actions involving healthy eating, physical activity and sleeping habits. The virtual world participants reported positive changes in all the healthy eating and physical activity measures except the number of hours slept.
"They also had more confidence in their ability to perform physical activity in difficult situations, such as bad weather, vacations, low-energy days," Johnston said.
"It's counter-intuitive, the idea of being more active in a virtual world, but the activities that they do in a virtual world can carry over into the real world," said Jeanne Johnston, assistant professor of kinesiology at Indiana University. "Through visualization and education, they can try activities that they had not tried before."
More and more people have been turning to online weight-loss programs, but Johnston said the programs often lack important elements of human interaction. The IU researchers wanted to travel even farther into cyber space by evaluating a weight-loss program offered in a virtual-reality environment, where visitors use avatars to interact with others or the computer-simulated environment -- in this case, a simulated fitness club.
"The virtual world program was at least as beneficial as the face-to-face program and in some ways, more effective," Johnston said. "It has the potential to reach people who normally wouldn't go to a gym or join a program because of limitations, such as time or discomfort with a fitness center environment."
The findings in the study "Comparison of a Face-to-Face versus Virtual World Weight Loss Program" will be discussed on Friday at the American College of Sports Medicine annual meeting in Denver. They will be presented during a poster presentation in Hall B from 8-9:30 a.m. MDT.
For 12 weeks, members of the each weight-loss program spent at least four hours a week attending meetings at a virtual or real club. In both they learned about nutrition, physical activity, changing habits and how to benefit from social supports. The study involved overweight and obese people -- mostly women. The average age of the face-to-face group was 37. The average age of the virtual world group, which provided training in how to use the Web-based platform Second Life, http://secondlife.com/, was 46.
The participants in each group lost a comparable amount of weight -- on average almost 10 pounds -- and saw similar decreases in body mass index and body fat. The big differences between the two groups involved behaviors. Participants in the face-to-face group reported no significant changes in any of the behaviors evaluated -- actions involving healthy eating, physical activity and sleeping habits. The virtual world participants reported positive changes in all the healthy eating and physical activity measures except the number of hours slept.
"They also had more confidence in their ability to perform physical activity in difficult situations, such as bad weather, vacations, low-energy days," Johnston said.
Blueberries may inhibit development of fat cells
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The benefits of blueberry consumption have been demonstrated in several nutrition studies, more specifically the cardio-protective benefits derived from their high polyphenol content. Blueberries have shown potential to have a positive effect on everything from aging to metabolic syndrome. Recently, a researcher from Texas Woman's University (TWU) in Denton, TX, examined whether blueberries could play a role in reducing one of the world's greatest health challenges: obesity. Shiwani Moghe, MS, a graduate student at TWU, decided to evaluate whether blueberry polyphenols play a role in adipocyte differentiation, the process in which a relatively unspecialized cell acquires specialized features of an adipocyte, an animal connective tissue cell specialized for the synthesis and storage of fat. Plant polyphenols have been shown to fight adipogenesis, which is the development of fat cells, and induce lipolysis, which is the breakdown of lipids/fat. Moghe will present her research at the Experimental Biology 2011 meeting for the American Society for Nutrition on Sunday, April 10, at 12:45 pm.
"I wanted to see if using blueberry polyphenols could inhibit obesity at a molecular stage," said Moghe. The study was performed in tissue cultures taken from mice. The polyphenols showed a dose-dependent suppression of adipocyte differentiation. The lipid content in the control group was significantly higher than the content of the tissue given three doses of blueberry polyphenols. The highest dose of blueberry polyphenols yielded a 73% decrease in lipids; the lowest dose showed a 27% decrease.
"We still need to test this dose in humans, to make sure there are no adverse effects, and to see if the doses are as effective. This is a burgeoning area of research. Determining the best dose for humans will be important," said Moghe. "The promise is there for blueberries to help reduce adipose tissue from forming in the body."
These preliminary results contribute more items to the laundry list of benefits related to blueberries, which have already been shown to mitigate health conditions like cardiovascular disease and metabolic syndrome.
The benefits of blueberry consumption have been demonstrated in several nutrition studies, more specifically the cardio-protective benefits derived from their high polyphenol content. Blueberries have shown potential to have a positive effect on everything from aging to metabolic syndrome. Recently, a researcher from Texas Woman's University (TWU) in Denton, TX, examined whether blueberries could play a role in reducing one of the world's greatest health challenges: obesity. Shiwani Moghe, MS, a graduate student at TWU, decided to evaluate whether blueberry polyphenols play a role in adipocyte differentiation, the process in which a relatively unspecialized cell acquires specialized features of an adipocyte, an animal connective tissue cell specialized for the synthesis and storage of fat. Plant polyphenols have been shown to fight adipogenesis, which is the development of fat cells, and induce lipolysis, which is the breakdown of lipids/fat. Moghe will present her research at the Experimental Biology 2011 meeting for the American Society for Nutrition on Sunday, April 10, at 12:45 pm.
"I wanted to see if using blueberry polyphenols could inhibit obesity at a molecular stage," said Moghe. The study was performed in tissue cultures taken from mice. The polyphenols showed a dose-dependent suppression of adipocyte differentiation. The lipid content in the control group was significantly higher than the content of the tissue given three doses of blueberry polyphenols. The highest dose of blueberry polyphenols yielded a 73% decrease in lipids; the lowest dose showed a 27% decrease.
"We still need to test this dose in humans, to make sure there are no adverse effects, and to see if the doses are as effective. This is a burgeoning area of research. Determining the best dose for humans will be important," said Moghe. "The promise is there for blueberries to help reduce adipose tissue from forming in the body."
These preliminary results contribute more items to the laundry list of benefits related to blueberries, which have already been shown to mitigate health conditions like cardiovascular disease and metabolic syndrome.
Wednesday, June 1, 2011
Low-carb, higher-fat diets add no arterial health risks to obese people seeking to lose weight
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Overweight and obese people looking to drop some pounds and considering one of the popular low-carbohydrate diets, along with moderate exercise, need not worry that the higher proportion of fat in such a program compared to a low-fat, high-carb diet may harm their arteries, suggests a pair of new studies by heart and vascular researchers at Johns Hopkins.
"Overweight and obese people appear to really have options when choosing a weight-loss program, including a low-carb diet, and even if it means eating more fat," says the studies' lead investigator exercise physiologist Kerry Stewart, Ed.D.
Stewart, a professor of medicine and director of clinical and research exercise physiology at the Johns Hopkins University School of Medicine and its Heart and Vascular Institute, says his team's latest analysis is believed to be the first direct comparison of either kind of diet on the effects to vascular health, using the real-life context of 46 people trying to lose weight through diet and moderate exercise. The research was prompted by concerns from people who wanted to include one of the low-carb, high-fat diets, such as Atkins, South Beach and Zone, as part of their weight-loss program, but were wary of the diets' higher fat content.
In the first study, scheduled to be presented June 3 at the annual meeting of the American College of Sports Medicine in Denver, the Hopkins team studied 23 men and women, weighing on average 218 pounds and participating in a six-month weight-loss program that consisted of moderate aerobic exercise and lifting weights, plus a diet made up of no more than 30 percent of calories from carbs, such as pastas, breads and sugary fruits. As much as 40 percent of their diet was made up of fats coming from meat, dairy products and nuts. This low-carb group showed no change after shedding 10 pounds in two key measures of vascular health: finger tip tests of how fast the inner vessel lining in the arteries in the lower arm relaxes after blood flow has been constrained and restored in the upper arm (the so-called reactive hyperemia index of endothelial function), and the augmentation index, a pulse-wave analysis of arterial stiffness.
Low-carb dieters showed no harmful vascular changes, but also on average dropped 10 pounds in 45 days, compared to an equal number of study participants randomly assigned to a low-fat diet. The low-fat group, whose diets consisted of no more than 30 percent from fat and 55 percent from carbs, took on average nearly a month longer, or 70 days, to lose the same amount of weight.
"Our study should help allay the concerns that many people who need to lose weight have about choosing a low-carb diet instead of a low-fat one, and provide re-assurance that both types of diet are effective at weight loss and that a low-carb approach does not seem to pose any immediate risk to vascular health," says Stewart. "More people should be considering a low-carb diet as a good option," he adds.
Because the study findings were obtained within three months, Stewart says the effects of eating low-carb, higher-fat diets versus low-fat, high-carb options over a longer period of time remain unknown.
However, Stewart does contend that an over-emphasis on low-fat diets has likely contributed to the obesity epidemic in the United States by encouraging an over-consumption of foods high in carbohydrates. He says high-carb foods are, in general, less filling, and people tend to get carried away with how much low-fat food they can eat. More than half of all American adults are estimated to be overweight, with a body mass index, or BMI, of 26 or higher; a third are considered to be obese, with a BMI of 30 or higher.
Stewart says the key to maintaining healthy blood vessels and vascular function seems – in particular, when moderate exercise is included -- less about the type of diet and more about maintaining a healthy body weight without an excessive amount of body fat.
Among the researchers' other key study findings, to be presented separately at the conference, was that consuming an extremely high-fat McDonald's breakfast meal, consisting of two English muffin sandwiches, one with egg and another with sausage, along with hash browns and a decaffeinated beverage, had no immediate or short-term impact on vascular health. Study participants' blood vessels were actually less stiff when tested four hours after the meal, while endothelial or blood vessel lining function remained normal.
Researchers added the McDonald's meal challenge immediately before the start of the six-month investigation to separate any immediate vascular effects from those to be observed in the longer study. They also wanted to see what happened when people ate a higher amount of fat in a single meal than recommended in national guidelines. Previous research had suggested that such a meal was harmful, but its negative findings could not be confirmed in the Johns Hopkins' analysis. The same meal challenge will be repeated at the end of the study, when it is expected that its participants will still have lost considerable weight, despite having eaten more than the recommended amount of fat.
"Even consuming a high-fat meal now and then does not seem to cause any immediate harm to the blood vessels," says Stewart. However, he strongly cautions against eating too many such meals because of their high salt and caloric content. He says this single meal -- at over 900 calories and 50 grams of fat -- is at least half the maximum daily fat intake recommended by the American Heart Association and nearly half the recommended average daily intake of about 2,000 calories for most adults.
All study participants were between the age of 30 and 65, and healthy, aside from being overweight or obese. Researchers say that in the first study, because people were monitored for the period they lost the same amount of weight, any observed vascular differences would be due to what they ate.
Overweight and obese people looking to drop some pounds and considering one of the popular low-carbohydrate diets, along with moderate exercise, need not worry that the higher proportion of fat in such a program compared to a low-fat, high-carb diet may harm their arteries, suggests a pair of new studies by heart and vascular researchers at Johns Hopkins.
"Overweight and obese people appear to really have options when choosing a weight-loss program, including a low-carb diet, and even if it means eating more fat," says the studies' lead investigator exercise physiologist Kerry Stewart, Ed.D.
Stewart, a professor of medicine and director of clinical and research exercise physiology at the Johns Hopkins University School of Medicine and its Heart and Vascular Institute, says his team's latest analysis is believed to be the first direct comparison of either kind of diet on the effects to vascular health, using the real-life context of 46 people trying to lose weight through diet and moderate exercise. The research was prompted by concerns from people who wanted to include one of the low-carb, high-fat diets, such as Atkins, South Beach and Zone, as part of their weight-loss program, but were wary of the diets' higher fat content.
In the first study, scheduled to be presented June 3 at the annual meeting of the American College of Sports Medicine in Denver, the Hopkins team studied 23 men and women, weighing on average 218 pounds and participating in a six-month weight-loss program that consisted of moderate aerobic exercise and lifting weights, plus a diet made up of no more than 30 percent of calories from carbs, such as pastas, breads and sugary fruits. As much as 40 percent of their diet was made up of fats coming from meat, dairy products and nuts. This low-carb group showed no change after shedding 10 pounds in two key measures of vascular health: finger tip tests of how fast the inner vessel lining in the arteries in the lower arm relaxes after blood flow has been constrained and restored in the upper arm (the so-called reactive hyperemia index of endothelial function), and the augmentation index, a pulse-wave analysis of arterial stiffness.
Low-carb dieters showed no harmful vascular changes, but also on average dropped 10 pounds in 45 days, compared to an equal number of study participants randomly assigned to a low-fat diet. The low-fat group, whose diets consisted of no more than 30 percent from fat and 55 percent from carbs, took on average nearly a month longer, or 70 days, to lose the same amount of weight.
"Our study should help allay the concerns that many people who need to lose weight have about choosing a low-carb diet instead of a low-fat one, and provide re-assurance that both types of diet are effective at weight loss and that a low-carb approach does not seem to pose any immediate risk to vascular health," says Stewart. "More people should be considering a low-carb diet as a good option," he adds.
Because the study findings were obtained within three months, Stewart says the effects of eating low-carb, higher-fat diets versus low-fat, high-carb options over a longer period of time remain unknown.
However, Stewart does contend that an over-emphasis on low-fat diets has likely contributed to the obesity epidemic in the United States by encouraging an over-consumption of foods high in carbohydrates. He says high-carb foods are, in general, less filling, and people tend to get carried away with how much low-fat food they can eat. More than half of all American adults are estimated to be overweight, with a body mass index, or BMI, of 26 or higher; a third are considered to be obese, with a BMI of 30 or higher.
Stewart says the key to maintaining healthy blood vessels and vascular function seems – in particular, when moderate exercise is included -- less about the type of diet and more about maintaining a healthy body weight without an excessive amount of body fat.
Among the researchers' other key study findings, to be presented separately at the conference, was that consuming an extremely high-fat McDonald's breakfast meal, consisting of two English muffin sandwiches, one with egg and another with sausage, along with hash browns and a decaffeinated beverage, had no immediate or short-term impact on vascular health. Study participants' blood vessels were actually less stiff when tested four hours after the meal, while endothelial or blood vessel lining function remained normal.
Researchers added the McDonald's meal challenge immediately before the start of the six-month investigation to separate any immediate vascular effects from those to be observed in the longer study. They also wanted to see what happened when people ate a higher amount of fat in a single meal than recommended in national guidelines. Previous research had suggested that such a meal was harmful, but its negative findings could not be confirmed in the Johns Hopkins' analysis. The same meal challenge will be repeated at the end of the study, when it is expected that its participants will still have lost considerable weight, despite having eaten more than the recommended amount of fat.
"Even consuming a high-fat meal now and then does not seem to cause any immediate harm to the blood vessels," says Stewart. However, he strongly cautions against eating too many such meals because of their high salt and caloric content. He says this single meal -- at over 900 calories and 50 grams of fat -- is at least half the maximum daily fat intake recommended by the American Heart Association and nearly half the recommended average daily intake of about 2,000 calories for most adults.
All study participants were between the age of 30 and 65, and healthy, aside from being overweight or obese. Researchers say that in the first study, because people were monitored for the period they lost the same amount of weight, any observed vascular differences would be due to what they ate.
Does Liposuction Get Rid of That Forever? More Like a Year
Liposuction has become one of the most popular plastic surgeries in the United States. It has been around since 1974 and there are now more than 450,000 operations a year. But does the fat come back? A recent study by Teri L. Hernandez, PhD, RN and Robert H. Eckel, MD, at the University of Colorado School of Medicine have found that the fat eventually returns within one year, and is redistributed to other areas of the body, especially the upper abdomen. There was further redistribution around the shoulders and triceps of the arms.
"The fact that fat returned is of great interest to us as scientists. It supports the idea that levels of body fat are very tightly regulated by mechanisms we have yet to uncover," said Eckel. "This was the hypothesis we were testing and it was confirmed. In rodents when fat is removed it returns, and after weight loss in humans most everyone regains the weight. We think the brain somehow knows how much fat is on board and responds in a manner to regulate that weight. That's why preventing obesity is so important."
The study was a difficult one to execute because fat must be measured precisely with expensive scans that require multiple resources and considerable manpower. The University of Colorado is one of a handful of institutions that could facilitate this type of highly controlled study. Obesity researchers said that they are not surprised the fat came back. Data in animal models have shown that after surgical removal of fat, it tends to return to other areas. The liposuction study performed at the University of Colorado is the first randomized controlled trial in humans.
"We must emphasize that liposuction surgery is not a weight loss procedure. Our research participants are wonderful women who sought to change their shape through liposuction. Despite fat returning, their cosmetic shape benefit was retained and they have been very happy with their surgery results," said Hernandez.
This paper was published in the latest issue of Obesity.
"The fact that fat returned is of great interest to us as scientists. It supports the idea that levels of body fat are very tightly regulated by mechanisms we have yet to uncover," said Eckel. "This was the hypothesis we were testing and it was confirmed. In rodents when fat is removed it returns, and after weight loss in humans most everyone regains the weight. We think the brain somehow knows how much fat is on board and responds in a manner to regulate that weight. That's why preventing obesity is so important."
The study was a difficult one to execute because fat must be measured precisely with expensive scans that require multiple resources and considerable manpower. The University of Colorado is one of a handful of institutions that could facilitate this type of highly controlled study. Obesity researchers said that they are not surprised the fat came back. Data in animal models have shown that after surgical removal of fat, it tends to return to other areas. The liposuction study performed at the University of Colorado is the first randomized controlled trial in humans.
"We must emphasize that liposuction surgery is not a weight loss procedure. Our research participants are wonderful women who sought to change their shape through liposuction. Despite fat returning, their cosmetic shape benefit was retained and they have been very happy with their surgery results," said Hernandez.
This paper was published in the latest issue of Obesity.
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