Dr. Jeff Horowitz directs the Substrate Metabolism Laboratory (SML). His laboratory studies the regulation of fat, carbohydrate, and protein metabolism in humans, with particular interest in how exercise and diet affect energy metabolism. Dr. Horowitz’s laboratory studies whole-body and regional lipid, glucose, and amino acid metabolism in human subjects using stable-isotope tracers, microdialysis, and indirect calorimetry. In addition, Dr. Horowitz's laboratory examines cellular regulation of substrate metabolism in skeletal muscle and adipose tissue. The combination of these approaches provides a powerful tool to identify cellular variations in tissues and the associated alterations in systemic or tissue-specific substrate metabolism. Therefore, this integrated approach makes it possible to associate cellular adaptations to exercise with clinical outcomes, which could lead to improved methods to treat chronic diseases or to advancements in "healthy aging."