Does carrying a gene tied to obesity doom a teenager to becoming obese? Not if that teen stays physically active, a new study shows.

Among genes related to obesity, mutations in the so-called fat mass-and-obesity-associated gene (FTO) appear to be particularly important. In fact, each copy of a mutation in this gene has been tied to an average jump in weight of about 3.3 pounds, the researchers say.

However, an hour of physical activity a day largely negated the gene's effect, the new study found.

"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 [gene variant] in adolescents," said lead researcher Jonatan R. Ruiz, a scientist in physical activity and fitness epidemiology at the Karolinska Institute in Huddinge, Sweden.

The report is published in the April issue of the Archives of Pediatrics & Adolescent Medicine.

For teens who got at least an hour of physical activity each day, the effect of the obesity-linked gene mutation on weight was much smaller, Ruiz said.

Exercise also helped trim back gene-linked increases in body fat mass and waist circumference, the study found.

Ruiz' advice to teens worried about excessive weight gain? "Be active. Try to do at least 60 minutes of moderate and vigorous physical activity every day -- like playing sports," he said.

p>Source: US News & World Report
http://www.usnews.com/health/diet-fitness/fitness/articles/2010/04/05/exercise-helps-teens-overcome-obesity-gene.html