Adolescent overweight and obesity have increased dramatically in the past several decades. High schools are well-positioned to deliver weight loss treatment to overweight and obese adolescents, as they have the facilities and staff to deliver a physical activity program, school nurses with the skills to provide counseling, and are easily accessible by adolescents. This exploratory study will test the feasibility and ability of a school-based intervention, consisting of school nurse counseling and a school-based exercise program, to reduce BMI and improve dietary quality, physical activity, and sedentary behaviors in overweight and obese adolescents. If effective, this could prove to be a cost-effective and relatively easy intervention to disseminate widely for significant public health impact.