Scientists may have figured out one reason some people reach for the french fries instead of an apple. It could be a gene that's been linked to an increased risk of obesity. A study of children found those with a common variation of the gene tend to overeat high-calorie foods. They ate 100 extra calories per meal, which over the long term can put on weight, said Colin Palmer, who led the study at the University of Dundee in Scotland.

The findings don't mean that everyone with that version of the gene will eat too much and become obese, he said. They just might have a tendency to eat more fattening foods.

"It's still your choice," he said. "This gene will not make you overweight if you do not overeat."

Palmer said the results support the theory that childhood obesity today could be connected to the widespread availability and low cost of high-calorie foods. The research is published in Thursday's New England Journal of Medicine.

Last year, scientists discovered the gene, named FTO, was linked to obesity but they didn't know why. Most of the other genes thought to affect body weight influence appetite.

Palmer and his colleagues wanted to know if the FTO gene also had to do with eating behavior, or whether it involved how the body burns calories. They studied over 2,700 Scottish children ages 4 to 10 and put a group of them through extensive tests.

Nearly two-thirds of the children had at least one copy of the gene variant, about the same proportion found in last year's study of mostly white Europeans. That study found that those with one copy of the gene variant had a 30 percent increased risk of obesity, and carriers of two copies had almost a 70 percent increased risk.

The gene variation is also found in other populations; the frequency in Chinese is about half that of Europeans.

After confirming the obesity link in the larger Scottish group, the researchers examined 97 of the children. They took a number of measurements, including body fat and metabolic rate.