Diet and Exercise in Type 2 Diabetes and Prediabetes

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.

This study will enroll people who are overweight or obese and have type 2 diabetes or prediabetes. Participants will attend a baseline study visit and complete blood pressure measurements; muscle strength measurements; a treadmill test to evaluate cardiovascular fitness; an echocardiogram to obtain images of the heart; tests to measure blood vessel function; a dual energy x-ray absorptiometry (DEXA) scan to measure body fat, muscle tissue, and bone density; questionnaires to assess physical activity levels, quality of life, and mood; and a blood collection. A portion of blood will be stored for future genetic testing. Women will also provide a urine sample for pregnancy testing. Participants will also keep a food diary for 3 days. Participants will then be randomly assigned to either a weight loss diet group or a weight loss diet plus exercise group. All participants will attend study visits with a dietitian for weight loss counseling once a week during Months 1 and 2, and every other week in Months 3 through 6. At each of these visits, participants' weight will be measured. Blood pressure measurements will also occur at least once a month.

Participants who are assigned to the diet plus exercise group will also attend a supervised exercise session three times a week for 6 months. Each session will last 1 to 1 ½ hours and will include aerobic exercise and weight training. Participants who have diabetes or who are receiving medication to control their blood sugar will have their blood sugar measured before and after exercising, based on study staff recommendations. At the end of Month 6, all participants will attend a study visit for repeat baseline testing.