TUESDAY, Jan. 8, 2012 — Ever wonder why your skinny friend can chow down on hamburgers while remaining as skinny as a French fry?
Genetics might be the answer, say researchers at the University of California, Los Angeles in the journal Cell Metabolism. Overall, the amount of food consumed contributes only modestly to the degree of obesity, they say, meaning that whether a diet high in fast food causes weight gain for individuals is largely determined by genetics and is largely hereditary.
"Our research demonstrates that body-fat responses to high-fat, high-sugar diets have a very strong genetic component, and we have identified several genetic factors potentially regulating these responses," said first author Brian Parks, MD, in a university release. "We found that obesity has similar genetic signatures in mice and humans, indicating the mice are a highly relevant model system to study obesity. Overall, our work has broad implications concerning the genetic nature of obesity and weight gain."
For the study, genetically inbred mice were placed on a normal diet for the first eight weeks of life and were subsequently switched to a high-fat, high-sugar diet for eight weeks. During the period of the high-fat diet, some mice gained no body fat while others gained upward of 600 percent of their initial body fat. Most mice gained fat during the first four weeks of the high-fat feeding and then did not gain additional weight, suggesting a set point where continued body fat gain is resisted by genetic mechanisms, researchers said in the paper.
Whether the mice gained any body fat was heritable across 80 percent of cases, researchers also noted, supporting the hypothesis that genetics determine how a mouse (or perhaps, a human) gain fat.
These results are consistent with the inheritance of body mass index and obesity seen in humans and emphasize the importance of genetics in controlling obesity, the study authors concluded. Although they also note that other factors besides diet and genetics can contribute to obesity, the key conclusion is that there is a strong link between DNA and the amount of fat gained when a high-calorie, high-sugar diet is consumed.
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