Quantifying the Persistence of Metabolic Adaptation and Weight Regain Following Extreme Weight Loss

Overview

Background: Many people regain the weight they lose through diet and exercise. This might happen because the weight loss slows their metabolism. This slowing is called metabolic adaptation. It may cause people to regain weight if they do not keep up high levels of exercise or major caloric restrictions. Researchers want to find the long-term effects of metabolic adaptation in the previous Biggest Loser study participants. They hope to learn the body s response to lifestyle changes that result in weight loss. They also want to see if certain changes can lead to longer-term success in maintaining weight loss. Objectives: To better understand the long-term metabolic changes caused by rapid weight loss achieved through diet restriction and vigorous physical activity. Eligibility: Former Biggest Loser research study participants (Protocol No. PBRC29008). Design: Participants will be screened with a phone interview. This study has 3 phases. Phase 1 will last at least 3 weeks. Participants will receive a physical activity monitor and wireless scale. These will send their daily weight and activity back to NIH. In Phase 2, participants will stay at NIH for 3 days. Their metabolism will be measured through: Their activity monitor Urine samples and daily body weight Medical review and physical exam Fasting for 12 hours each night for a blood draw the following morning DEXA: a low-dose x-ray of the body BIS: Electrodes on the hand/wrist and foot/ankle measure body water content. Phase 3 will last at least 3 weeks. Participants will: Continue to monitor their daily weight and activity Collect urine samples and send them back to NIH

Weight loss is accompanied by a slowing of metabolic rate. Metabolic slowing often occurs to a degree greater than predicted by the amount of weight lost, a phenomenon called metabolic adaptation , and is hypothesized to persist over time and promote weight regain. We previously discovered large metabolic adaptations in response to the intensive lifestyle intervention as part of The Biggest Loser weight loss competition. Those subjects rapidly lost massive amounts of weight and their resting energy expenditure decreased by \~500 kcal/d more than was expected based on their body composition at the end of the intervention. The purpose of this study is to investigate whether the metabolic adaptation has persisted in the years following the intervention in the same subjects. Furthermore, we will measure body weight and composition in these subjects and investigate the correlates of weight regain.