A recent study that analyzes the effects of exercise in the Amish community of Lancaster County, Pennsylvania, shows that three to four hours of moderate daily exercise like brisk walking or house and yard work can override the genetic variation that predisposes some people to excessive weight gain.

The genetic variant exists in about 30 percent of individuals of European ancestry, including some of the Swiss-German Amish. The 19th century lifestyle of the Amish of Pennsylvania, which is mostly devoid of modern conveniences, was chosen because of the high level of daily activity (Lindsey Tanner, "3-4 Hours of Exercise Might Fool Fat Gene," Associated Press, Sept. 9, 2008).

Experts recommend that those who tend to gain weight easily should look for ways to add extra activity and walking to their day to counteract the gene.