Immediate Weight Loss Program Group If the participant is placed in the Immediate Weight Loss Program group, the participant will participate in the weight loss program soon after signing up for the study. The program consists of 15 sessions focused on reducing calories and increasing exercise. Sample goals of the program include reducing weight by 1-2 pounds per week and increasing exercise to at least 150 minutes of moderate exercise (such as walking) per week. Weight loss sessions will take place once per week for 15-weeks at Dana-Farber. The participant will meet with a dietician and exercise specialist weekly during the sessions to set diet and exercise goals for the week. Each session will consist of discussion of a diet and/or exercise topic for 30 minutes and 30 minutes of group exercise, such as moderate-paced walking or step aerobics. The participant will also be given the opportunity to be weighed, either as part of the group or in private with one of the weight loss study staff members, at each session in order to track their progress.