Adolescents who meet physical activity recommendations may offset genetic obesity predisposition

Adolescents who partake in one hour or more of physical activity per day may offset the effect of fat mass and the obesity-associated gene FTO.

Researchers in Sweden conducted a cross-sectional study to examine whether current physical activity recommendations minimized the effects of mutations in the FTO gene on body fat in adolescents. The U.S. Department of Health and Human Services guidelines recommend at least one hour of moderate- to vigorous-intensity physical activity per day for children and adolescents.

The study included 752 adolescents who were part of the Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study. Researchers genotyped the FTO gene, assessed physical activity by accelerometry and also measured weight, height, waist circumference, triceps, subscapular skinfolds, BMI and body fat percentage.

Thirty-seven percent of adolescents did not have the FTO rs9939609 polymorphism; 47% had one copy of the mutation; and 16% had two copies.

Adolescents who had the gene mutation also had a higher BMI (0.42 per risk allele), body fat percentage (1.03% per risk allele) and waist circumference (0.85 cm per risk allele) compared with adolescents who did not have the mutation.

However, among adolescents who met the daily physical activity requirements, the effect of the gene mutation was much lower. For each copy of the mutated gene, adolescents who performed one hour or more of daily physical activity had a BMI an average of 0.17 higher than those with no mutations, compared with 0.65 higher per mutation among those who did not meet physical activity requirements. Further, each mutated gene was associated with a 0.4% body fat increase and 0.6-cm increase in waist circumference among those who met physical activity guidelines compared with a 1.7% increase in body fat and a 1.15 cm increase in waist circumference among those who did not.

The researchers also identified significant gene x physical activity interactions for body fat percentage estimates for BMI (P=.02), body fat percentage (P=.06) and waist circumference (P=.10).

“These findings have important public health implications and indicate that meeting the physical activity recommendations may offset the genetic predisposition to obesity associated with the FTO polymorphism in adolescents,” the researchers wrote.

Ruiz JR. Arch Pediatr Adolesc Med. 2010;164:328-333.

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