The Effects of Aerobic and Resistance Exercise Training on the Cardiometabolic Health of Adolescents with Obesity

Abstract

Physical inactivity and obesity in adolescence are associated with an increased risk of cardiovascular disease (CVD). Although exercise is recommended for the management of obesity, we know little about which types of exercise training are the most effective in reducing excess body fat and improving CVD risk in obese adolescents. This dissertation examined the effects of aerobic training, resistance training and their combination on the cardiometabolic health (body composition, CVD risk markers, resting metabolic rate (RMR), and fitness) of obese adolescents who participated in the Healthy Eating Aerobic and Resistance Training in Youth (HEARTY) trial. After a 4-week supervised moderate-intensity exercise run-in period, 304 overweight and obese adolescents were randomized to 4 groups for 22 weeks: Aerobic training, Resistance training, Combined aerobic and resistance exercise training, or a non-exercising Control. All four groups received dietary counseling designed to promote healthy eating with a maximum daily energy deficit of 250 kcal. Participants were assessed at baseline and after 3 and 6 months. Body composition was assessed using magnetic resonance imaging. Blood tests for traditional and non-traditional CVD risk markers were measured after a 12-hour fast. RMR and cardiorespiratory fitness were assessed using indirect calorimetry at rest and during a maximal treadmill test respectively. Musculoskeletal fitness (muscular strength, endurance, flexibility) was assessed using eight repetition maximum tests (8-RM) on the leg press, chest press and upright row machines and using the Canadian Society for Exercise Physiology- Canadian Physical Activity Fitness and Lifestyle Appraisal (CSEP-CPAFLA) tests for grip strength, push-ups, sit-ups, sit and reach and vertical jump. Decreases in percent body fat and abdominal fat were greatest in the combined training group. Although body weight, RMR and traditional CVD risk markers did not improve following the exercise intervention, the combined training group showed improvements in cardiorespiratory and musculoskeletal fitness and some non-traditional CVD risk markers. Cumulatively, combined aerobic and resistance exercise training showed the greatest improvements in cardiometabolic health in overweight and obese adolescents. This thesis concludes with a knowledge translation article detailing the practical lessons learned from exercise interventions with obese youth with hopes of increasing adherence to future exercise programs and improving the overall health of children and adolescents with obesity.