In this study, doctors want to find out more about why people who lose weight often regain the weight that they have lost once they resume a regular diet and whether hormones might play a role in weight regain. The study is divided into two parts, called the meal replacement period and the follow-up period. The meal replacement period will consist of drinking a shake for breakfast and lunch and eating a frozen meal for dinner that is calorie controlled. Individuals will also be asked to eat two servings of fruit and three servings of vegetables each day. The study will provide the shakes and the frozen entrees, participants are asked to supply the fruits and vegetables. Participation in this study will last for up to 35 weeks. There will be 10 in-person visits and 13 visits by phone or over Zoom over the 35 weeks.