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If identical twins eat and exercise equally, must they have the same body weight" By analyzing the fundamental equations of body weight change, NIH researchers Carson Chow and Kevin Hall find that identical twins with identical lifestyles can have different body weights and different amounts of body fat.

The study, published March 28th in the open-access journal PLoS Computational Biology, uses a branch of mathematics called dynamical systems theory to demonstrate that a class of model equations has an infinite number of body weight solutions, even if the food intake and energy expenditure rates are identical. However, the work also shows that another class of models directly refutes this, predicting that food intake and energy expenditure rates uniquely determine body weight. Existing data are insufficient to tell which is closer to reality, since both models can make the same predictions for a given alteration of food intake or energy expenditure.

Given the ongoing obesity epidemic, Drs. Chow and Hall are interested in what factors determine human body weight and its stability. Of particular importance is whether a therapy for obesity would have to be administered repeatedly over a lifetime or could be given only until a target body weight is reached. As a particular example, the study considers whether weight lost from a liposuction procedure is permanent. For the class of equations with an infinite number of body weight solutions, fat removal through liposuction could lead to permanent results. However, the opposing models predict that the body would eventually return to its original weight.

Chow and Hall note that neither class of models accounts for the a number of variables affecting how much a person tends to eat, an important factor determining bodyweight. Nevertheless, for any food intake rate this latest research suggests that an individual may have an infinite number of possible body weights. The study outlines the mathematical conditions underlying this possibility and suggests how future experiments could determine if it is true.


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New Haven, Conn.Discrimination against overweight peopleespecially womenis as common as racial discrimination, as per a research studyby the Rudd Center for Food Policy & Obesity at Yale University.

These results show the need to treat weight discrimination as a legitimate form of prejudice, comparable to other characteristics like race or gender that already receive legal protection, said Rebecca Puhl, research scientist and lead author.

The study documented the prevalence of self-reported weight discrimination and compared it to experiences of discrimination based on race and gender among a nationally representative sample of adults aged 25- to 74-years-old. The data was obtained from the National Survey of Midlife Development in the United States.

The study also revealed that women are twice as likely as men to report weight discrimination and that weight discrimination in the workplace and interpersonal mistreatment due to obesity is common.

The scientists observed that men are not at serious risk for weight bias until their body mass index (BMI) reaches 35 or higher, while women begin experiencing a notable increase in weight discrimination risk at a BMI level of 27. BMI is the measure of body fat based on height and weight.

Co-author Tatiana Andreyava of Yale said weight discrimination is more prevalent than discrimination based on sexual orientation, nationality/ethnicity, physical disability, and religious beliefs. However, despite its high prevalence, it continues to remain socially acceptable, she said.


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More than half of American adults considered to have normal body weight in America have high body fat percentages -- greater than 20 percent for men and 30 percent for women -- as well as heart and metabolic disturbances, new Mayo Clinic research shows. The finding conflicts with the widely held belief that maintaining a normal weight automatically guards against disorders such as high levels of circulating blood fats and a tendency to develop metabolic syndrome, which often leads to type 2 diabetes.

The scientists defined normal weight by body mass index (BMI). They observed that people with normal BMI who had the highest percentage of body fat were also those who had metabolic disturbances associated with heart disease. The scientists use the phrase normal weight obesity to describe this new type of patient at risk for metabolism problems and risk factors for heart disease, but who rates as normal on standard weight charts. They defined normal weight obesity as a condition of having a normal BMI with high body fat percentage. The Mayo team will present its study results at the American College of Cardiologys Annual Scientific Session next week in Chicago.

Using the term normal weight obesity is really a way of being more precise about the changing conceptualization of obesity, because the real definition of obesity is excess body fat, says Francisco Lopez-Jimenez, M.D., a heart specialist on the Mayo research team. Our study demonstrates that even people with normal weight may have excessive body fat, and that these people are at risk for metabolic abnormalities that lead to diabetes and, eventually, to heart disease.


Significance of the Mayo Clinic Study
Heart disease remains the major cause of death and disability in westernized countries. Scientists around the world are striving to refine the relationship of body composition to heart health as a means of:

• Designing more effective risk assessment tools.
  
• Improving public health programs for reducing risk.
  
• Designing new and better clinical rehabilitation programs for heart patients

While a focus on maintaining a healthy weight has long been a centerpiece of these efforts, Mayos new study suggests the focus may need to shift. Instead of tracking weight and BMI only, public health measures to prevent heart disease might benefit more from measuring the belly or by assessing percentage of body fat as more reliable risk factors of heart disease. Mayo studies in 2006 and 2007 suggested this criterion by demonstrating the inability of BMI to discriminate between body fat and lean muscle. Combined, the data from our earlier work and the current study suggest its time for a new measure of body fat as a risk factor of heart disease, says Dr. Lopez-Jimenez.


About the Study.

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The scientists studied 2,127 adults, equally divided between men and women, who had normal weight (BMI between 18.5 and 24.9 units). The participants body composition was assessed, and their risk factors for metabolic and heart disease were collected by the U.S. government in its Third National Health and Nutrition Examination Survey http://www.cdc.gov/nchs/products/elec_prods/subject/nhanes3.htm.

From this data, scientists observed that normal weight obesity appears to be highly prevalent, affecting more than half of patients with a normal weight as defined by the BMI. After controlling for age, sex and race, normal weight obesity subjects had significantly higher rates of several alterations in blood chemistry that can negatively affect heart and metabolism health. These markers of disregulation include:.

• Altered blood lipid profile, such as cholesterol.
  
• High leptin, a hormone found in fat and other tissues and is involved in appetite regulation.
  
• Higher rates of metabolic syndrome

Posted by: Evelyn    Source

Overweight but active men responded dramatically better in comparison to their inactive counterparts in a first-of-its kind study from Indiana University that examined the vascular response to exercise in overweight men.

Vascular function is important because of its relationship to cardiovascular disease.

The active cohort saw an average 24 percent improvement in their vascular function, in comparison to the 32 percent decrease observed in the inactive group. The results were reported in the journal "Obesity."

"This overweight-obesity phenomenon is an epidemic in today's society," said Ryan A. Harris, who led the study while a doctoral student in the School of Health, Physical Education and Recreation's Department of Kinesiology. "This study supports that being consistent with daily physical activity is beneficial to cardiovascular health. Being active may not drop the pounds as quickly as you'd like, but it still is beneficial".

Obesity contributes to a variety of diseases, including diabetes and heart disease.

"But being overweight isn't hopeless," said Janet P. Wallace, professor of exercise physiology in the Department of Kinesiology. "This study shows you can still do some measures to help yourself while you work to lose weight."

The study involved 16 overweight men ages 46-68. Half were active, performing at least 30 minutes of moderate activity on most days. For the study, they performed low, moderate or high intensity treadmill walking for 45 minutes. The scientists examined the brachial artery flow-mediated dilation -- how well the artery can expand to accommodate an increase in blood flow. The brachial artery was examined because it has been correlation to coronary function. The beneficial effect observed in the active group lasted for about an hour, said Harris, now a post-doctoral research fellow in the Department of Medicine at the University of California in San Diego.

Wallace said this is the first study to examine the vascular effect of exercise in overweight men despite the growing belief among some health and fitness experts that active, overweight people might be healthier in some ways than lean, sedentary people. She said managing weight is still important because of the relationship between obesity and a host of diseases and conditions.

Co-authors of the study are Jaume Padilla, doctoral student in IU's Department of Kinesiology, Kevin P. Hanlon, an undergraduate student in the department, and Lawrence D. Rink, M.D., with Internal Medicine Associates in Bloomington.

The study was supported by the Gatorade Sports Science Institute and a research grant in aid from the School of HPER. For a copy of the study, contact press@nature.com. For additional assistance, contact Tracy James, 812-855-0084 and traljame@indiana.edu.

Wallace can be reached at 812-855-6384 and wallacej@indiana.edu. Harris can be reached at 858-534-4713 and Harrisra@ucsd.edu.

"The Flow-mediated Dilation Response to Acute Exercise in Overweight Active and Inactive Men," Obesity, Jan. 2008, doi:10.1038/oby.2007.120.


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You may want to buy healthy food for your family, but if the good grocery stores are far away and pricey and the fast-food outlets are cheap and plentiful, it may be harder to make the healthy choice. Research led by the University of Alberta and funded by the Canadian Institute for Health Information confirms there are links between our urban surroundings and how likely we are to struggle with obesity.

The startling rise in obesity rates in North America over the past two decades has led to calls for more effective approaches to help people achieve healthy weights. The State of the Evidence Review on Urban Health and Healthy Weights, released to the public this week, synthesizes the findings of hundreds of population health studies published over the years and shines a spotlight on aspects of our urban environments that can either inhibit or promote our ability to maintain a healthy weight.

Two key areas we looked at were economic environments and built environmentsmeaning the ways in which the neighbourhoods and the cities in which we live are planned and developed, said Kim Raine, director of the University of Albertas Centre for Health Promotion Studies and lead author of the report.

When we evaluated the evidence we found, for example, that lower-income neighbourhoods were more likely to have greater access to sources of high-calorie foods, such as fast-food outlets, and lower access to supermarkets or other stores stocking healthy foods, explained Raine. The report also observed that a lower socio-economic statuswhich involves education level, income and employmentwas often linked to increased obesity among both adults and children. Lower personal income affects the affordability of food, Raine said, and that has been shown to have the most consistent influence on what people eat.

The walkability of neighbourhoods and access to recreational facilities in and around neighbourhoods may also assist in promoting healthy weights, as per the report. Some hallmarks of walkability are increased residential density, mixed-use zoning and street connectivity, said co-author John Spence from the U of As Faculty of Physical Education and Recreation. On the other hand, factors such as urban sprawl, low intersection density, low residential density and low land-use mix tend also to favour sedentary behaviour and lower physical activity levels and promote obesity.

The report also observed that individuals living in middle-income to high-income neighbourhoods were more likely to be physically active than their counterparts in lower-income neighbourhoods.

Raine, Spence and their fellow scientists conclude that interventions aimed at improving the income and educational status of individuals and families within urban environments may help address these disparities in obesity. And improving access to healthy foods and recreation opportunities in lower-income neighbourhoods can also help to create a healthy weight-friendly environment, Spence said.


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