Lack of physical activity is not the cause of weight gain in children, according to a study in Archives of Diseases in Childhood. Researchers measured physical activity and body fat percentage in 202 children annually from age 7 to age 10. The amount of physical activity did not result in changes in body fat. Although physical activity is important, the researchers concluded that focusing on food intake may have a larger impact on weight loss.

Metcalf BS, Hosking J, Jeffery AN, Voss LD, Henley W, Wilkin TJ. Fatness leads to inactivity, but inactivity does not lead to fatness: a longitudinal study in children (EarlyBird 45). Arch Dis Child. Published ahead of print June 23, 2010. doi: 10.1136/adc.2009.175927.