Regaining weight after losing it is the most significant obstacle to treating obesity. Regular exercise has emerged as one of the most potent strategies for successful weight loss maintenance. Paul MacLean, PhD, from the University of Colorado Anschutz Medical Campus, will discuss his research on the effects of regular exercise on energy expenditure and nutrient trafficking during weight regain after weight loss through the use of with a Comprehensive Lab Animal Monitoring System (Oxymax®-CLAMS). This system allows for comprehensive phenotyping to establish a picture of how regular exercise affects energy balance, whole body metabolism and the molecular profiles of key metabolic tissues.