Teenagers trying to lose weight should engage in an exercise program that includes both aerobic and resistance training, a randomized trial has found. It also found that diet without exercise accomplishes little.
Canadian researchers put 304 obese teenagers on a diet with a daily energy deficit of 250 calories (measured from their resting energy expenditure). Then they assigned them randomly to one of four groups for 22 weeks: aerobic training on exercise machines like treadmills, resistance exercise using weight machines and free weights, combined aerobic and resistance training, and a diet-only group with no exercise. The study appeared in JAMA Pediatrics.
Aerobic exercise is usually recommended, but the lead author, Dr. Ronald J. Sigal, a professor of medicine at the University of Calgary in Alberta, said it is clear that “those who did both resistance and aerobic exercise had significantly more fat loss and decreased waist size than those who did aerobic exercise alone.”
Diet alone produced a 0.6 percent decline in body fat. But among adolescents who were at least 70 percent adherent to the programs, body fat decreased 2.5 percent for aerobic exercise, 3.2 percent for resistance, and 4.8 percent for the two combined. Waist circumference went down insignificantly in the diet group, but declined 1.2 inches for aerobic exercise, 0.8 inches for resistance, and 1.6 inches for the combined program.
An earlier version of this post misstated the name of the institution at which the lead author of the study works. It is the University of Calgary, not Calgary University.