Mapping Metabolic Organ Plasticity in Energy Adaptation

Brief Summary (Plain Language) Many people who lose weight experience a slowdown in their metabolism that is greater than expected. This response, called metabolic adaptation, makes it harder to continue losing weight or to keep weight off over time. The biological reasons for this slowdown are not fully understood. Some organs in the body, especially the liver and kidneys, use a large amount of energy even when the body is at rest. Although these organs make up only a small portion of body weight, they account for a large share of daily energy use. Changes in the size or function of these organs may play an important role in metabolic adaptation, but this has not been well studied in humans. The purpose of this study is to understand how different lifestyle approaches affect metabolic adaptation and the size of key metabolic organs. Specifically, the study compares three common strategies: * resistance training without calorie restriction, * a calorie-restricted diet, and * time-restricted eating (eating all daily food within a limited time window). Adults with overweight will take part in one of these approaches for 10 weeks. Before and after the study period, participants will undergo advanced measurements, including magnetic resonance imaging (MRI) scans to measure liver and kidney size, tests to measure resting metabolism, and assessments of body composition. Some participants will also undergo additional testing to measure daily energy use. By understanding how different lifestyle strategies influence metabolism and organ size, this study aims to improve knowledge about why weight loss is difficult to maintain and to support the development of more personalized approaches to long-term weight management.