Girls’ weight gains linked to inactivity

Adolescent girls in the United States are putting on weight because they are doing less physical activity than they did as children, a study has found.

Research by scientists at the University of New Mexico in Albuquerque showed that increasing exercise to the equivalent of two to five hours of brisk walking each week could help prevent girls from gaining nine to 20 pounds in their teens.

“Preventing the steep decline in activity during adolescence is an important method to reduce obesity,” said Sue Y.S. Kimm, the lead researcher in a study published online last week by the Lancet medical journal.

Kimm and her team studied body mass index, skin folds and changes in physical activity in more than 2,200 girls from three U.S. cities who were followed from the ages of 9 to 19. The girls also filled in a questionnaire about their physical activity and eating habits.