BEST EXERCISE FOR OBESE YOUTHS ANALYZED
What exercise program
can best fight the "epidemic" of teen obesity? According to a study
published in the Journal of the American
Medical Association (JAMA) Pediatrics, by combining aerobic exercise with resistance training
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 overweight
teens in the Ottawa/Gatineau area between the ages of 14 to 18. All were given
the same four weeks of diet counseling to promote healthy eating and weight
loss before being randomly placed into 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.
"Obesity is an
epidemic among youth," says Dr. Ron Sigal of the University of Calgary's
Institute for Public Health and Libin Cardiovascular Institute of Alberta.
"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."
In the overall study
population, each type of exercise reduced body fat significantly and similarly.
All three exercise programs caused significantly more fat loss than in the
diet-only control group. Among youths who 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 of the University of Ottawa. "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."
Supervised by personal
trainers, youths in the three exercise groups were asked to train four times
per week for 22 weeks at community-based facilities. 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.
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.
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