Overweight and obese children who dedicate at least an hour a day to exercising may improve their metabolic health, but they won't shed fat, found researchers here.

 Exercise No Panacea for Overweight Children but May Kick Start Metabolism

By Peggy Peck, Executive Editor, MedPage Today
Published: June 30, 2008
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco

PLYMOUTH, England, June 30

Action Points 

•   Explain to interested patients that this report suggests that exercise at the current recommended level for children does not decrease BMI or slim waists.
•    Explain to interested patients that this study demonstrated that girls and boys improve metabolic function with exercise.

A longitudinal study of 113 boys and 99 girls found that only 11% of girls and just 42% of boys met guideline requirements for daily exercise, and those who did were not rewarded with a significant change in body mass index, investigators reported in online in the Archives of Disease in Childhood.

Boys and girls who regularly exercised had a small, but significant, improvement in composite metabolic score (P<0.01) and that improvement was more pronounced among the most active children compared with less active children (P<0.001), wrote Brad S. Metcalf, B.Sc., of Derriford Hospital, and colleagues.

Current guidelines in the United States and England recommend that children exercise at least once a day for 60 minutes or more at an intensity of at least three metabolic equivalents of thermogenesis (METs) or more.

Although girls were less likely to exercise than boys, those who did reaped the same benefits as boys.

The improvement in metabolic health was evident when exercise intensity exceeded three METs, which suggests that "girls in particular should be encouraged to do more, or the recommendations [should be] adjusted for girls," they wrote.

The children were participants a non-intervention prospective cohort study of 307 healthy children (170 boys) who were recruited at age five and followed annually through age eight. Most of the children were white (98%).

The 212 children included in this analysis had physical activity, changes in BMI, fatness (skin-fold and waist circumference) and metabolic status (insulin resistance, triglycerides, cholesterol/HDL ratio, and blood pressure) measured at age five, six, seven, and eight.

At baseline the mean BMI for boys was 16.3 and for girls it was 16.2. The mean waist circumference was 51.5 cm (20.27 inches).
The authors cautioned that BMI, which is a measure of both fat and lean mass, "may be an inappropriate outcome measure for assessing changes in physical activity as any decrease in fat mass may have been off-set by an increase in lean mass."

But they added that both skin-fold and waist circumference measures found no decrease in fat mass.

The study was funded by Diabetes U.K., Bright Futures Trust, Smiths Charity, Child Growth Foundation, Diabetes Foundation, Beatrice Laing Trust, Abbott, AstraZeneca, GSK, Ipsen, and Roche. The authors declared no conflicts.

Primary source: Archives of Disease in Childhood

Source reference:
Metcalf BS, et al "Physical activity at the government-recommended level and obesity-related health outcomes: a longitudical study (Early Bird 37)" Arch Dis Child DOI: 10.1136/adc.2007.135012.