February 2010
If you're not overweight and want to stay that way, you may need to exercise even more than the 150 minutes per week that federal guidelines recommend. And if you're already overweight, it may be too late for exercise to get you slim — although physical activity can still have important benefits against chronic disease. Those were the depressing findings of a new analysis of data on 34,079 healthy US women, average age 54, from the Women's Health Study. Over an average follow-up of 13 years, the women gained an average of nearly 6 pounds. Among the 13.3% who gained less than this, the average amount of exercise was 60 minutes daily — 420 minutes a week — of moderate physical activity, such as brisk walking (or half as much intense exercise, such as jogging). Physical activity was associated with reduced weight gain, but only among normal-weight women; for those with a BMI of 25 and up, exercise had no effect on weight control. The women maintained a "usual diet," suggesting that if you can't carve out an hour for activity daily, the only way to keep the pounds off is restricting calories. — JAMA
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