This randomized phase III trial studies whether weight loss in overweight and obese women may prevent breast cancer from coming back (recurrence). Previous studies have found that women who are overweight or obese when their breast cancer is found (diagnosed) have a greater risk of their breast cancer recurring, as compared to women who were thinner when their cancer was diagnosed. This study aims to test whether overweight or obese women who take part in a weight loss program after being diagnosed with breast cancer have a lower rate of cancer recurrence as compared to women who do not take part in the weight loss program. This study will help to show whether weight loss programs should be a part of breast cancer treatment.