Obesity Gene Discovered in Humans
Obesity researchers have long known that calorie for calorie, some folks put on weight more easily than others, and genes play a large role. Now comes the strongest evidence yet that a particular gene may be partially responsible. In a study published in Thursday's online edition of the journal Science, British researchers reported that a single variation in the FTO gene raises the overweight risk by about 20 percent and the obesity risk by about 30 percent compared with people wit hout the variation. Having two variations (one in each FTO gene in the double-stranded chromosome) raises the risks by about 40 percent and 70 percent, respectively. About 60 percent of those with European ancestry carry at least one altered gene, the study found.
Many prior studies that have linked specific genes to body weight have crumbled when researchers tried to repeat them. It's a problem of cause and effect: Does a gene actually cause obesity, or does it just occur more often in obese people? Although the current study lacks proof of either, researchers repeatedly found a connection between body mass index and a glitch in the FTO gene in the genetic profiles of nearly 40,000 people. "The reason we're so convinced is that we've done this 13 times in 13 different groups of people" with similar results, says study coauthor Mark McCarthy, a professor of diabetes, endocrinology, and metabolism at the University of Oxford. The groups included diabetics (who tend to be overweight), healthy adults, and children.
"It is the strongest evidence I've seen yet, by far, for an association," says David Allison, a professor of biostatistics at the University of AlabamaBirmingham who reviewed the study before publication. But he adds, "The influence of one single gene is likely to be quite small." Whether the gene actually influences weight-control mechanisms like appetite or metabolism remains unknown, so dreams of new drugs to deactivate the altered form are wishful thinking. The findings shouldn't deter those trying to shed pounds with diet and exercise, says McCarthy. Still, it might be comforting to have evidence that their extra efforts are because of their genes, not their lack of willpower.