Aerobic and/or Resistance Exercise Improves Fitness and Body Composition Interview with:
Angela Alberga, PhD
Eyes High Postdoctoral Fellow
Werklund School of Education
University of Calgary

Ronald J. Sigal, MD, MPH, FRCPC
Professor of Medicine, Kinesiology, Cardiac Sciences and Community Health Sciences
Division of Endocrinology and Metabolism, Cumming School of Medicine, University of Calgary
Health Senior Scholar, Alberta Innovates-Health Solutions
Member, O’Brien Institute of Public Health, Libin Cardiovascular Institute and Julia McFarlane Diabetes Research Centre

Medical Research: What are the main findings of the study?

Response: The Healthy Eating, Aerobic and Resistance Training in Youth study examined the effects of exercise on body composition and cardiometabolic risk markers in adolescents with obesity. A total of 304 overweight or obese adolescents were randomized to four groups. The first group performed resistance training involving weight machines and some free weights; the second performed only aerobic exercise on treadmills, elliptical machines and stationary bikes; the third underwent combined aerobic and resistance training; and the last group did no exercise training. All four groups received nutritional counseling. In analyses involving all participants regardless of adherence, each exercise program reduced percent body fat, waist circumference and body mass index to a similar extent, while the diet-only control group had no changes in these variables. In participants who exercised at least 2.8 times per week, we found that combined aerobic and resistance training produced greater decreases in percentage body fat, waist circumference, and body mass index than aerobic training alone. Waist circumference decreased close to seven centimeters in adherent participants randomized to combined aerobic plus resistance exercise, versus about four centimeters in those randomized to do just one type of exercise, with no change in those randomized to diet alone.

Medical Research: What was most surprising about the results?

Response: One surprise was that we saw significant body composition improvements in spite of less than optimal overall adherence. We asked exercise group participants to work out 4 times per week, but the median number of sessions completed was only about 2.4 per week. Nevertheless, modest but clinically and statistically significant favorable changes were observed.

Another surprise was that, despite the improvements in body composition, there were no significant changes in body weight, HDL and LDL cholesterol, triglycerides, blood pressure, fasting glucose, and HemoglobinA1c. This can possibly be explained by the fact that most of our participants had normal glucose tolerance HbA1c and lipids at baseline, leaving little room for improvement.

Medical Research: What should clinicians and patients take away from your report?

Response: Aerobic exercise, resistance exercise and their combinations each had significant favorable effects on body composition and fitness. Adolescents who want to maximize the health benefits of exercise should ideally perform both aerobic and resistance exercise 3-4 times per week, but significant benefit can still be achieved through either type of exercise alone.

Medical Research: What recommendations do you have for future research as a result of this study?

Response: The results of this study improved our understanding of the effects of aerobic exercise, resistance exercise and their combination on body composition and cardiovascular disease risk factors in adolescents with obesity. Future research should evaluate the effects of exercise training in adolescents who have metabolic complications associated with their obesity to determine if there are differences in their responses to exercise. Future studies should also examine the long-term effects and adherence to structured exercise programs into adulthood.


Sigal RJ, Alberga AS, Goldfield GS, et al. Effects of Aerobic Training, Resistance Training, or Both on Percentage Body Fat and Cardiometabolic Risk Markers in Obese Adolescents: The Healthy Eating Aerobic and Resistance Training in Youth Randomized Clinical Trial. JAMA Pediatr. 2014;168(11):1006-1014. doi:10.1001/jamapediatrics.2014.1392.

Last Updated on November 5, 2014 by Marie Benz MD FAAD