Regular exercise may trump the obesity gene in teens

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Genetics may be one factor that causes obesity, but according to a new study those genes might not hold sway over an adolescent’s weight--if that teen exercises.

Researchers looked at data on 752 teens who took part in the Health Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study. The participants were tested to see if they had one or two copies of a gene mutation that may be linked with obesity. It’s thought that each mutation of the gene is linked to about a 3.3-pound heavier body weight, and the estimated risk for this gene among whites is about 40%.

In the adolescent study group, 37% had no copies of the mutated gene, 47% had one copy, and 16% had two copies. Having the gene mutation was associated with a higher body mass index, a higher body fat percentage, and a larger waist circumference.

However, researchers noticed physiological differences among the teens when they looked at how much activity they got. Among those who did at least an hour a day of moderate to vigorous exercise, the gene was not linked with a higher BMI, higher body fat percentage, or larger waist size. Those who had the gene and did less than hour of exercise had higher BMIs, body fat percentage and larger waist circumferences. The U.S. Department of Health and Human Services recommends that children and teens exercise at least an hour a day, most of it at a moderate to vigorous level.

In the study, each copy of the mutated gene was linked with an average 0.65 higher BMI among those who exercised less than an hour a day, versus 0.17 among those who exercised at least an hour a day. Among those who met the exercise recommendations, each gene mutation was associated with an increase of 0.4% body fat and 0.6-centimeter larger waist circumference. Among those who exercised less than an hour, the increases were 1.7% and 1.15 centimeters, respectively.

The study was released today in the journal Archives of Pediatrics & Adolescent Medicine.

-- Jeannine Stein

Teens exercise in a group cycling class.