How Much Exercise Prevents Weight Gain?

A new study from Harvard sheds some light on a perpetual question: how much exercise is needed to avoid gaining weight. More than 30,000 healthy women were surveyed every few years between 1992 and 2007. They followed their usual diet and were asked about their exercise. During the course of those 13 years, the average woman gained almost 6 pounds. But women of normal weight at the start of the study were less likely to add pounds if they exercised more. It took about an hour a day of moderate intensity activity to avoid gaining weight.
[JAMA, March 24/31, 2010]