WASHINGTON - Researchers have found another gene that may keep you from fitting in your jeans. You can't blame this gene, named FTO, for all the extra inches. But British scientists discovered that people who carry two copies of a variation of the FTO gene weighed, on average, 7 pounds more than people who lack it.

Unlike other genes thought to be involved with appetite or calorie burning, scientists have no idea yet what FTO is supposed to do.

But research published in Friday's edition of the journal Science shows strong evidence of a link. Using blood samples provided by more than 38,000 people, scientists found that those who had one copy of the gene variation had a 30 percent increased risk of obesity, and carriers of two copies had almost a 70 percent increased risk.

The study included mostly white Europeans, and about one in six of them are thought to carry two copies of the gene variant, concluded the British team, from the University of Oxford and the Peninsula Medical Center in Exeter.

About a third of American adults are obese, and millions more are overweight. Bad diets and too little exercise are the chief factors. But innate biology plays some role, and researchers are exploring a variety of genes and hormones that seem involved in the balancing act of weight gain and loss.

The work was funded by the Wellcome Trust, a British medical charity.