About 30 of  people of Northern European heritage have variations of a particular gene, known as the fat mass and obesity associated (FTO) gene, can predispose them to be overweight. But does this genetic predisposition guarantee fat? Apparently not, at least not if people exercise.

Researchers at the University of Maryland studied DNA samples from 704 healthy Amish adults, average age 43.6. Fifty-four percent of men and 63.7 percent of women were overweight, while 10.1 percent of men and 30.5 percent of women were obese. The participants were also fitted with “accelerometers,” measuring their precise movements over a period of time.

The researchers surprisingly found that Amish people with the genetic variant were no more likely to be overweight than those who had the regular version of the gene as long as they exercised three to four hours every day (that included moderate activity such as brisk walking, housecleaning and gardening).

The authors concluded in the September 8 issue of the journal Archives of Internal Medicine, confirming once again that staying active keeps pounds away.

“Our results strongly suggest that the increased risk of obesity due to genetic susceptibility can be blunted through physical activity. Some of the genes shown to cause obesity in our modern environment may not have had this effect a few centuries ago when most people’s lives were similar to that of present-day Amish farmers,” Dr. Soren Snitker, of the University of Maryland and lead-author of the research, said:

“These findings emphasize the important role of physical activity in public health efforts to combat obesity, particularly in genetically susceptible people.”