The mice were eating their usual chow and exercising normally, but they were getting fat anyway. The reason: researchers had deleted a gene that acts in the brain and controls how quickly calories are burned. Even though they were consuming exactly the same number of calories as lean mice, the mice were gaining weight.
So far, only one person – a severely obese child – has been found to have a mutation in the same gene that completely disables it. But the discovery of the same effect in mice and in the child – a finding published Wednesday in Science – may help explain why some people put on weight easily while others eat all they want and seem never to gain an ounce. It may also offer clues to a puzzle in the field of obesity: Why do studies find that people gain different amounts of weight while overeating by the same amount?
Scientists have long thought explanations for why some people get fat might lie in their genes. They knew body weight was strongly inherited. Years ago, for example, they found twins reared apart tended to have similar weights and adoptees tended to have weights like their biological parents, not the ones who reared them. As researchers developed tools to look for the actual genes, they found evidence that many – maybe even hundreds – of genes may be involved, stoking appetites, making people voraciously hungry.
Read a report at the New York Times.