In the fight against obesity, exercise rules. New research reveals in the lands of Pennsylvania's Amish, one obesity gene has no effect if carriers are very active.

Researchers compared a very physical group of Amish men and women against a less active Amish group holding more conventional jobs (e.g., factory work). All participants carried FTO, an obesity-related gene. The very physical group weighed about the same as others not carrying the gene, while members of the less active group were significantly more likely to be overweight or obese. The most physically active Amish burned about 900 more calories a day than the less active group.

Hand-plowing five acres isn't exactly a realistic strategy to prevent obesity, but it does illustrate the power of daily, vigorous exercise. Researchers suspect modern living has turned genes we've been carrying for years into liabilities.