Brigham and Women's Hospital researchers studied more than 34,000 women starting at an average age of 54. They followed their activity level for 13 years. The women were divided into three groups. Those exercising 60, 30 and less than 30 minutes daily.
"These two lesser activity groups of women were significantly more likely to gain weight compared to the most active group of women," said Dr. I-Min Lee, Brigham and Women's Hospital.
And women had to be near their ideal weight to reap the benefits.
"We found that physical activity was effective in controlling weight only among women who started off with a normal BMI," Dr. Lee. "The women who were overweight or obese, physical activity, with the range done in the study was not sufficient to control their weight."
For heavier women, researchers say don't let the 60 minutes of daily exercise discourage you from starting or continuing to exercise. It helps reduce the risk of many chronic diseases.
Researchers also add that women in the study consumed a regular American diet and did not restrict their calories.