Aerobic and resistance training fights teen obesity
According to the American Heart Association using BMI values on the CDC growth chart, the prevalence of overweight in adolescents ages 12–19 increased from 6.1 percent to 18.4 percent. John Hopkins explains Adolescents live sedentary lives. Teens spend the school day mostly sitting, and then go on to spend an average of three more hours’ parked in front of a TV or computer screen. Teens are participating in either moderate or vigorous physical activity. Little evidence exists on which exercise modality is optimal for obese adolescents.
According to Dr. Ronald J. Sigal, MD, MPH, FRCPC, Professor of Medicine, Cardiac Sciences, Kinesiology and Community Health Sciences, University of Calgary, Obesity is an epidemic among youth.” “Adolescents who are overweight are typically advised to exercise more, but there is limited evidence on what type of exercise is best in order to lose fat.”
The Healthy Eating Aerobic and Resistance Training in Youth (HEARTY) study, led by researchers at the University of Calgary and University of Ottawa, involved 304 participants of previously inactive post pubertal adolescents aged 14 to 18 years .
All participants received dietary counseling, with a daily energy deficit of 250 calories for four weeks. Participants were randomly assigned to one of four groups for 11 weeks; aerobic training (75 participant’s) that consisted of aerobic exercise on treadmills, elliptical machines and stationary bikes; the second group (8 participant’s) performed resistance training involving weight machines and some free weights, the third group (75 participants) underwent combined aerobic and resistance training and the last group (6 participant’s) had no exercise and served as the control group.
Participants in the exercise groups were supervised by trainers. Changes in body fat were measured using Magnetic Resonance Imaging (MRI) machines. Because aerobic exercises such as cycling or jogging can be challenging for overweight people, resistance training is potentially attractive because excess body weight poses far less of a disadvantage, and gains in strength come much more quickly than gains in aerobic fitness.
In the overall study population, each type of exercise reduced body fat significantly and similarly. All three exercise groups had significantly more fat loss compared to the control group. Among the teens who had completed at least 70 per cent of the study’s exercise sessions, the percentage of body fat decreased “significantly more in those who did combined aerobic and resistance exercise than in those who only did aerobic exercise,” says co-principal researcher Dr. Glen Kenny, PHD, professor of the School of Human Kinetics at the University of Ottawa’s Faculty of Health Sciences. He continues “Remarkably, among participants who completed at least 70 per cent of the prescribed exercise sessions, waist circumference decreased close to seven centimeters in those 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.”
The research team noted that “In more adherent participants, combined training may cause greater decreases than aerobic or resistance training alone.
Researchers hope that the study will contribute to a national debate about childhood and teenage obesity, potentially leading to a consistent, long-term strategy on how to best deal with the problem. Eighty per cent of overweight youth typically continue to be obese as adults, adversely affecting the quality of their lives and contributing to chronic disease problems. Adult obesity increases risk of diabetes, heart disease, cancer and disability.
Aerobic Training, Resistance Training, or Both on Percentage Body Fat and Cardiometabolic Risk Markers in Obese Adolescents. JAMA Pediatrics, 2014; DOI: 10.1001/jamapediatrics.2014.1392
Public Release University of Calgary, Faculty of Medicine