A new study led by a Northwestern researcher shows inactivity may not affect a child’s amount of body fat, but lack of exercise can increase it greatly.

The lead author of the study is Soyang Kwon, an NU research assistant professor in pediatrics at the Feinberg School of Medicine.

Kwon and her co-authors from the University of Iowa based their conclusions on data about 554 children in Iowa from 2000 to 2009 showing their body fat and their body movement levels, according to Reuters Health.

The study showed 13-year-old girls who exercised sparingly gained seven pounds more body fat than those who exercised more regularly. For 13-year-old boys, those who exercised little gained 11 more pounds. However, 13-year-olds who sat for 6.5 hours per day all had about the same body fat.

The research was recently published in the Journal of Pediatrics.

— Ally Mutnick