Genetic Predispositon and its Effect on Obesity
4/05/06
Isabel Gardocki
Carnegie Mellon University
Contrary to the suggestions of popular weight loss commercials, shedding extra pounds fast might not be such an easy task. In fact, in the long term, it may not be possible at all. According to the findings presented by University of South Florida researcher Barbara Hansen, PhD, maintaining a lean physique requires a rigorous, lifelong effort of balancing total calories consumed and total calories expended [1].
Dr. Hansen, a physiologist and psychologist specializing in obesity, diabetes and their age-related health complications, spoke at the Feb. 17 annual meeting of the American Association for the Advancement of Science in St. Louis. She had studied the effects of calorie restriction in about 300 rhesus monkeys over a twenty-year period and concluded that the weight struggle is heavily influenced by genetic predisposition [2]. Even monkeys kept on low-fat, low-cholesterol diets with fiber supplements became overweight or obese in the laboratory [3]. "Obesity is a primate disease," said Dr. Hansen, adding that undomesticated monkeys are also not immune from the obesity epidemic.
Yet, Dr. Hansen emphasized that there is no "single cause" hypothesis for obesity [1]. Neither genetics alone nor a poor diet or inactivity can account for the weight gain. "Obesity is a continuum that develops early or late, quickly or slowly," she said. Each person may have a "set" point for weight, regardless of media advertisements to the contrary. "Your body has a natural tendency is to return to its individually programmed body composition," explained Dr. Hansen. In her studies, monkeys that had been forced to slim down by as much as 25 percent recovered their discarded pounds once the caloric clamp was lifted, whether they had been on the diet for two months or two years [2].
The initial few weeks of dieting can also be misleading to the concerned calorie counter. Checking the scale after a few days may suggest results; however, five of the most popular weight loss diets have shown only low levels of overall weight change, usually from 2 to 3 kilograms, said Dr. Hansen. Similarly to the reflux in rhesus monkeys, evidence suggests that 90 percent of human dieters recover their lost weight within five years, with a significant number regressing back in the first year alone [3]. This "recidivism," as Dr. Hansen calls it, is still little understood. It may be the result of a lack of will power, an increase in appetite, or a reduction in energy expenditure.
Yet, it seems that there is little the average American can do to combat the bulge. "We have all been sold on exercise, but not with valid data," Hansen said. Choosing exercise over dieting also does not lead to any substantial weight loss, although it may circumvent additional weight gain and lower susceptibility to cardiovascular disease and diabetes [3].
References:
[1] "Complexities Of Obesity, Diabetes And Their Age-related Complications Studied By Researcher" Medical News Today, February 21, 2006, http://www.medicalnewstoday.com/medicalnews.php?newsid=38059
[2] Fink, Danielle, "DIET: Watching Calories a Lifelong Commitment, Study Suggests." Cleveland Health News, February 18, 2006, http://www.wkyc.com/news/health/health_article.aspx?storyid=48018
[3] Raiford, Katie, "When It Comes to the Scale, Genes Hold Weight" Medill News Service, February 19, 2006, http://mesh.medill.northwestern.edu/mnschicago/archives/2006/02/when_it_comes_t_1.html
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