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NEW YORK (Reuters Health) - Sedentary overweight children who start exercising after school become more fit -- and may also be less likely to slam doors, hit other children, and express their anger in other aggressive ways, researchers report.
"It may help children control their anger, and that might be because they're in a better mood because they don't get angry as much, and it might also be an aspect of self-control," Dr. Catherine L. Davis of the Medical College of Georgia in Augusta, the lead researcher on the study, told Reuters Health.
While there's no evidence that overweight kids are significantly more aggressive than their normal-weight peers, they are more likely to be bullied or to bully others.
Given that exercise is known to help improve mood and reduce hostility in adults, Davis and her colleagues set out to determine if it might have the same effect in overweight young people.
They randomized 208 overweight, sedentary 7- to 11-year-old public school students to a no-exercise control group, 20 minutes of exercise daily, or 40 minutes of exercise for 10 to 15 weeks. Both exercise groups were bussed to and from the research gym, and spent 75 minutes there daily.
Children in both exercise groups scored lower on the Anger Out and Anger Expression components of the so-called Pediatric Anger Expression Scale after they had completed the program. Scores did not change in the control group.
The exercisers also increased their fitness levels. The amount of time the exercise groups were able to walk on a treadmill rose from an average of 485 seconds to 551 seconds, while for the control group treadmill time stayed about the same. The more a child's fitness increased, the greater his or her reduction in anger expression.
Getting attention from the program staff, being punished for behaving aggressively while participating in the program, and even spending less time watching violent shows on TV could all have been factors in why the children in the exercise group showed reductions in anger expression, the researchers say.
However, Davis points out, she and her colleagues have shown that overweight children who exercise regularly have improved cognitive function, which could translate to better anger control.
To better understand the independent effect of physical activity, the researchers are now conducting a 5-year, $3.6 million study funded by the National Heart, Lung and Blood Institute in which the control group will also come to the research gym, but will do arts and crafts and other activities that don't require them to break a sweat.
SOURCE: Pediatric Exercise Science, November 2008.