The Journal of American Medical Association published a study titled "Physical Activity and Weight Gain Prevention" in March 2010. In this study, they followed over 34,000 women from 1992-2007. These women were all over 45, and they were not given any dietary restrictions.
The women gained an average of 5.7 pounds over the course of the study. They found that women who started at a healthy weight, with a body mass index (BMI) under 25 achieved weight maintenance if they exercised moderately for 60 minutes every day.
Moderate exercise includes walking, riding a bike at a slower pace, or any activity that raises the heart rate moderately. Similar results were found for women who exercised intensely for 30 minutes a day, such as running, swimming, or participating in a gym workout.
Women who were overweight or obese with a BMI over 25 could not maintain weight with one hour of moderate exercise each day, suggesting dietary changes would need to be made to maintain weight.
Food for Thought? ummmm, let me rephrase that..... "words for thought"