Most of my work started with body composition and energy expenditure studies in children with Prader-Willi syndrome (PWS), but has progressed to children with all forms of obesity. My work has focused on the relationship with cardiovascular fitness and body composition in children, and includes school- based interventions to both assess, and improve cardiovascular fitness levels as well as insulin sensitivity. I have collaborated with the Wisconsin Department of Public Instruction on school-based interventions over the past 7 years. These studies have focused upon collaborations with schools, communities, and statewide agencies. I am also a founding member of the multidisciplinary University of Wisconsin Initiative to Prevent Obesity and Diabetes (WIPOD). I am the Medical Director of the Pediatric Fitness clinic, where I routinely recruit adolescents with obesity, low cardiovascular fitness, and insulin resistance for clinical studies.