Researchers report that news in the Dec. 11 edition of The New England Journal of Medicine.
That doesn't mean that people with the FTO gene variation are destined for obesity, or that other genes aren't also involved. Still, the FTO variant has attracted attention for its ties to obesity.
The new study confirms that connection and goes one step further to ask how the FTO gene influences obesity -- does it ramp up calorie consumption or dim calorie burning?
To find out, the researchers -- who included Joanne Cecil, PhD, of Scotland's University of Dundee -- studied some 2,700 elementary school kids in Scotland.
Cecil's team measured the children's height, weight, and waist and hip circumferences. They also checked the kids' FTO genes, based on saliva samples the students provided.
As expected, the heavier children were more likely to have the FTO gene variant. Their extra weight came from fat mass, not lean tissue.
The groundbreaking part of the study involved a subgroup of 76 students who got their metabolism monitored for 10 days and ate special test meals at the school. The researchers weighed the available food before and after those meals to see how much the kids had eaten.
Those tests showed the FTO variant didn't make for a sluggish metabolism, but it was linked to eating more food, especially high-calorie food, in the test meals.
So the FTO variant seemed to be involved in consumption of calories, not how the body handles those calories, note Cecil and colleagues.
For now, there's no need for a gene test to check for the FTO variant, according to an editorial published with the study. Lifestyle plays "an important role ... in enabling or restricting such susceptibility," writes editorialist Rudolph Leibel, MD, of the molecular genetics division and the Naomi Berrie Diabetes Center at Columbia University in New York.