CHICAGO -- Rev up the treadmill: Sobering research spells out just how much exercise women need to keep the flab off as they age -- and it's a lot.
At least an hour of moderate activity a day is needed for older women at a healthy weight who aren't dieting. For those who are overweight -- and that's most U.S. women -- even more exercise is called for to avoid gaining weight without eating less, the study results suggest.
"We all have to work at it. If it were easy to be skinny, we would all be skinny," said John Foreyt, a behavioral medicine expert who reviewed the study but wasn't involved in the research.
Brisk walking, leisurely bicycling and golfing are examples of moderate exercise. But don't throw in the towel if you can't do those things for at least an hour a day. Even a little exercise is good for your health even if it won't make you thin, the researchers said.
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Their findings are based on 34,079 nondieting middle-aged women, mean age 52, followed for about 13 years. The women gained an average of 6 pounds during the study.
Those who started at a healthy weight, with a body mass index less than 25, and who gained little or no weight during the study consistently got the equivalent of about an hour of moderate activity daily. Few women -- only 13 percent -- were in this category.
Few overweight women got that much exercise, and the results suggest that it wasn't enough to stop them from gaining weight.
"Talk to any group of women, and they all say the same thing," said Janet Katzin, 61, a "slightly overweight" marketing director from Long Island, N.Y., who exercises for an hour twice a week.
Thin as a younger adult, Katzin said the pounds started creeping up after she had her two children in the 1980s, despite exercising and watching what she eats. "It's just extremely frustrating and discouraging."
The study appears in today's Journal of the American Medical Association. Only women were studied, so the researchers from Harvard's Brigham and Women Hospital said it's uncertain whether the results would apply to men.
Hormonal changes in menopause can make women prone to weight gain, especially around the belly.