A new study has found that normal-weight, middle-aged women need to exercise an hour a day to prevent weight gain as they get older.
Researchers from Brigham and Women's Hospital and Harvard Medical School conducted the study, one of the first large-scale studies on exercise and weight control. They tracked the leisure-time physical activity and weight of more than 34,000 healthy middle-aged women over 13 years and concluded that women need an hour a day of moderate-intensity physical activity such as brisk walking to maintain their weight.
Women who participated were an average age of 54 at the start of the study, followed a regular diet and weren’t trying to lose weight. Researchers divided them into three groups:
- Active women doing at least 60 minutes a day of moderate-intensity physical activity, mostly walking.
- Moderately active women exercising at least 150 minutes a week
- Women exercising less than 150 minutes a week.
At the end of the study, 13 percent of participants turned out to be “successful weight maintainers,” meaning they did about 60 minutes a day of moderate-intensity exercise and gained less than 5 pounds at any checkpoint during the 13 years. Women in the less active groups were more likely to gain 5 pounds, and overweight and obese women were more likely to be less active. Overall, study participants gained an average of 6 pounds in the 13-year span.
Karen Sutton, MD, a Yale Medical Group orthopaedist and former athlete who specializes in women’s sports injuries, agreed that an hour a day is an excellent goal for many healthy, motivated women, but expressed concern that some women might give up on exercise if they set the bar too high.
“I do encourage most of my patients to do more aerobic and weight-bearing exercise as they get older, because metabolism does decrease, and they will need to increase exercise or limit calories to avoid gaining weight,” Sutton says. “But I wouldn’t necessarily encourage them to exercise for a particular number of minutes a day. A better strategy would be to figure out what their daily calorie intake is and match that with an exercise equivalent.”
Sutton often quotes 2008 U.S. physical activity guidelines that recommend adults get 2 hours and 30 minutes of moderate-intensity aerobic activity a week in addition to muscle-strengthening activities. She encourages women to use a pedometer to track their daily walking, and find an activity they like, such as cycling, jogging, swimming or walking, combined with a weight-training activity.
The Brigham and Women's Hospital and Harvard Medical School study was reported in an article in the Journal of the American Medical Association in March.