CHICAGO – One hour of moderate to vigorous exercise a day can help teenagers beat the effects of a common obesity-related gene with the nickname “fatso,” according to a new European study.

The message for adolescents is to get moving, said lead author Jonatan Ruiz of the Karolinska Institute in Sweden.

The study, released Monday, appears in the April edition of Archives of Pediatrics and Adolescent Medicine.

The research supports U.S. guidelines that tell children and teenagers to get an hour or more of physical activity daily, most of it aerobic activity such as running, jumping rope, swimming, dancing and bicycling.

Scientists are finding evidence that lifestyle and genes cause obesity and they’re just learning how much diet and exercise can offset the inherited risk.

One gene involved with obesity, the FTO gene, packs on the pounds when it shows up in a variant form. Adults who carry two copies of the gene variant — about one in six people — weigh on average 7 pounds more than people who don’t.

In the new study, 752 teenagers who had had their blood tested for the gene variant wore monitoring devices for a week during waking hours to measure their physical activity.

Exercising an hour or more daily made a big difference for the teenagers who were genetically predisposed to obesity. Their waist measurements, body mass index scores and body fat were the same, on average, as the other teenagers with regular genes.

But the teenagers with the gene variant had more body fat, bigger waists and higher BMI if they got less than an hour of exercise daily. The results were similar for boys and girls.

The teenagers lived in Greece, Germany, Belgium, France, Hungary, Italy, Sweden, Austria and Spain. The study was funded by the Spanish and Swedish governments and the European Union.