Type 2 diabetes and prediabetes are conditions that are largely caused by excess weight and physical inactivity. These conditions have adverse effects on heart and blood vessel structure and function, including left ventricular diastolic dysfunction, endothelial vasodilator dysfunction, and increased vascular stiffness, each of which increase the risk of cardiovascular disease. Reducing the amount of calories consumed and increasing physical activity are both important factors for losing weight, increasing fitness, and improving blood glucose control. However, little research has been conducted on the combined effects of diet and exercise on general and abdominal obesity, fitness, heart and blood vessel structure and function, and heart disease risk factors. The purpose of this study is to determine whether people who follow a diet program plus an exercise program experience better improvements in body composition and cardiovascular health than people who follow only a diet program.