Genetics plays role in obesity

As students pile their plates with often calorie-heavy food served to them by residential restaurants, scientists and doctors at UCLA and elsewhere are working to determine the relationship between an individual’s genetics and their probability of becoming obese.

Almost a quarter of people aged 20-39 are considered obese, according to a 2007 Center for Disease Control study.

“The causes of obesity are 100 percent genetic and 100 percent environmental,” said Simin Liu, a professor of epidemiology and the director of UCLA’s Program on Ergonomics and Nutrition. “The nature versus nurture debate has not been settled.”

Researchers are uncovering exactly which genes are the biggest predictors of potential obesity.

“This is a pattern of genetic predisposition which is complex and depends on many genes,” said Claude Bouchard, the director of the Pennington Biomedical Research Center in Baton Rouge, La. “The big question is which genes? Why do you have such an apparent genetic predisposition? This is where it gets complicated.”

Bouchard said that the lack of a certain key gene has been associated with between 5 and 6 percent of the obesity cases in the country. Deficiency in the gene leptin, for example, was found to be an excellent forecaster for future obesity.

The rest of the causes for obesity can be attributed to the interaction of defects in a number of other genes with the lifestyle and environment of these people, Bouchard said, pointing to such genes as FTO as strong susceptibility genes.

Bouchard said that there are about 20 such genes listed at the moment, but added that with the increase in research being conducted on this subject, this list will surely grow.

Family history has been shown to be another powerful predictor of obesity, said Wendy Slusser, a pediatrician at Mattel Children’s Hospital and the medical director of the UCLA Fit for a Healthy Weight Program.

“If you have overweight parents, you are considered to be more at risk for growing up to be overweight,” Slusser said. “That allows you to be more hypervigilant for promoting healthy behavior and a healthier diet (at a younger age).”

Slusser added that sedentary lifestyles, people’s ability to turn fat to fuel and hormonal changes also contribute.

Most scientists agree that obesity is not caused only by genetics, viewing the rise in obesity as a result of social causes.

“It’s a societal problem. It goes beyond genetics and biology,” Liu said, adding that various emphases of the modern lifestyle, such as driving over walking and taking an elevator over stairs, add to the rate of obesity.

Fighting excess weight at a young age is important, Bouchard said.

“Whether you are very much at risk to obesity or less predisposed, your body adapts to an obese state when you are obese,” he said. “You have to fight your own body, your hormones, your whole biology because it appears to like its state. The lesson we have already learned is that it pays off enormously to work on prevention (early).”

Liu said that the answer should come in preemptive measures that educate consumers about the health risks of calorie-heavy choices, comparing the struggle with obesity with the fight against tobacco.

“We need to prevent them before (they reach) the hospital,” he said. “The model’s already there with cigarettes.”

Slusser said that she maintains hope that the current trend toward increasing obesity can be reversed.

“If we have shifted our rate toward overweight, why can’t we shift back?” she said.

She noted that reducing one’s calorie intake by 150 each day would be significant enough to pause the rate of obesity.

“That’s the equivalent of 15 pieces of Doublemint gum or half a pack of M&Ms,” Slusser said. “It’s extremely doable.”

She added that, though obesity may be predicted by certain genes, this should not stop obese people from seeking treatment before their bodies adapt to their new size.

“A lot of people say, “˜Oh, it runs in my family,’ and chalk it up to that,” Slusser said. “But you can certainly improve the expression of your DNA.”

Leave a comment

Your email address will not be published. Required fields are marked *