Putative Obesity Gene Works Differently from Expected

Scientists have revealed a "genetic switch" that dictates if people will burn extra calories or save them as fat, according to an article published in the New England Journal of Medicine.

It was previously believed that the gene FTO worked in the brain to increase appetite. However, the researchers showed that the gene is not involved in obesity. They discovered that a genetic variant associated with obesity affects one of the introns in the FTO gene. The variant doubles the activity of genes IRX3 and IRX5, which are involved in determining which kind of fat cells will be produced.

"When researchers turned down activity of the IRX genes in human fat cells, the cells became energy-burning beige fat cells. Researchers also disrupted the IRX3 gene in fat cells of normal-weight mice. Those mice lost more than 50 percent of their body fat, even though they ate and exercised as much as other mice did. The mice were also protected from gaining weight on a high-fat diet. Disrupting the IRX3 gene in a part of the brain called the hypothalamus, which helps control appetite, did not have the same effect. That result indicates that the white-to-beige fat switch works in fat tissue, not in the brain," the report said.

Read the report from Science News and the journal article at the New England Journal of Medicine.