Participants will first attend a baseline study visit, at which time blood will be collected, and height, weight, waist circumference, and blood pressure will be measured. Questionnaires to assess medical history, physical activity levels, and dietary habits will be completed. An ultrasound will be used to evaluate blood vessel function and arterial stiffness. All participants will then take part in a 12-month behavioral and dietary intervention. The intervention will emphasize increasing physical activity and decreasing caloric intake by modifying lifestyle choices, physical and social environments, and attitudes toward food and exercise. Participants will be randomly assigned to follow either a low sodium diet or a normal sodium diet. During Months 1 through 4, participants will attend weekly study visits for group counseling sessions; during Months 4 through 8, study visits will occur once every two weeks; and during Months 8 through 12, they will occur once a month. At each study visit, weight, waist circumference, and blood pressure will also be measured. If necessary, individual counseling sessions will be scheduled. Participants will also document daily physical activity and caloric intake in a diary. Baseline evaluations will be repeated at Months 6, 12, and 24.