Exercise trumps obesity gene in study

CHICAGO (Reuters) - Vigorous physical activity can help even people genetically prone to obesity keep the weight off, U.S. researchers said on Monday.

They said a study among a group of Amish people found those who had an obesity-related gene called FTO but were very physically active weighed about the same as others who did not carry the gene.

"When we looked at the Amish who were the most active, there is suddenly no effect of that gene," said Dr. Soren Snitker of the University of Maryland, whose study appears in the Archives of Internal Medicine.

The findings, which suggest physical activity can overcome a genetic predisposition for obesity, may help inform the debate over whether changes in diet or physical activity will make the biggest difference in fighting obesity.

Consumer groups have pushed for laws such as July's moratorium on new fast-food restaurants in certain Los Angeles neighborhoods, while the food industry often maintains that a lack of exercise is more to blame.

Researchers focused their study on a group of 704 Old Order Amish men and women in Lancaster County, Pennsylvania, a religious group whose members often do not drive cars or have electricity in their homes.

Snitker said the group offered a unique mix of activity levels, with some farmers in the community still using horse-drawn plows while others holding more conventional jobs, including factory work.

He and colleague Evadnie Rampersaud of the University of Miami were looking to see if physical activity in this group might offset the effects of the fat mass and obesity associated with the FTO gene, found in more than half of all people of European descent.

RISK OF OBESITY

People with two copies of the FTO gene on average weigh nearly 7 pounds (3 kg) more and are about 70 percent more likely to be obese than those who do not have the gene.

The volunteers wore a device called an accelerometer to track motion for a week.

The researchers compared body mass index or BMI, a measure of weight to height, and found those who were less active and had the FTO gene variant were significantly more likely to be overweight or obese.

But among the most physically active, the FTO gene made no difference.

Snitker said the study gives some perspective on how the obesity epidemic has evolved, as modern conveniences have reduced the need and opportunity for physical activity.

People in the most physically active group expended about 900 more calories per day than the low-activity group. That would equal three to four hours of moderately intense physical activity such as brisk walking, house cleaning or gardening.

"We probably carry genes that 150 years ago were not risk factors for obesity, but because of changes in our environment, they become liabilities," he said.

Snitker believes societies should step in to make more opportunities for what he called "free" exercise, making it easier to walk or bike to work, or to use public transportation that requires some walking.

The World Health Organization estimates 1.6 billion adults worldwide are overweight and at least 400 million adults are obese. That includes a third of all U.S. adults.

(Editing by Maggie Fox and Todd Eastham)