Study: Obesity Caused by Faulty Gene, Not Diet

Researchers at UT Southwestern have identified a malfunctioning gene that caused mice to become obese despite their diet. A team of scientists that includes Nobel Laureate Dr. Bruce Beutler identified a genetic defect that may explain why some people gain weight without eating more than others.

Beutler co-led the study with Zhao Zhang, identifying a gene called Ovol2 that, when defective, caused mice with regular food intake and activity to become obese as they reached adulthood. The malfunction caused the mice to have problems generating body heat and burning off calories, even when exposed to cold. When researchers manifested the mutation, mice gained 556 percent more fat weight than mice without the gene, given the same amount of food and activity.

Researchers discovered the defect through random mutations in mice when the team found an extremely obese mouse, unlike any others found during the research. Obesity usually results from a mutation that causes mice to eat more, but the mouse with the Ovol2 mutation hadn’t eaten more than others.

“The first thing we noticed in a cold environment is that their temperature dropped dramatically,” Zhang says. “They cannot generate enough heat compared with other mice, which is the major reason they become obese.”

While the defect wasn’t enough to kill the mice, it had a severe metabolic impact. Conversely, when the gene was overexpressed the gene, researchers found that the mice gained less weight than the control…