The hardest part about starting a new exercise routine is just that: starting. But two new studies in the Journal of the American Medical Association should help get you off the couch. In the first, researchers put 184 sedentary, overweight women on diets of 1,200 to 1,500 calories a day and exercise plans of varying intensity that ranged in duration from 30 to 60 minutes a day. The scientists expected that more exercise would yield greater benefits, and it did. But to their surprise, the difference was only marginal. Even 30 minutes a day of moderate exercise, such as walking, led to a weight loss of 14 lbs. over a year. Women who worked out vigorously for an hour a day lost only 6 lbs. more. The second study, part of the Women's Health Initiative, showed that women who exercised moderately for 75 to 150 minutes a week were 18% less likely than inactive women to develop breast cancer. The more the women exercised, the more their risk declined, but once again the incremental difference was small. You don't have to run a marathon; you just have to get moving.