Vigorous Play Keeps the Pounds Off

Are fat people fat because they don't exercise enough? Or do they not exercise enough because they are fat? These questions are actually tougher to answer than you might suppose, as a study from the U.K. in the open-access journal PLoS: Medicine makes clear.

Investigators found that moderate to vigorous physical activity in a group of 5,500 12-year olds was associated with a lower risk of obesity. But the researchers couldn't say whether the kids were active because they were already slim. Or in their own words: "our study is cross-sectional and we cannot therefore rule out the possibility that these associations represent reverse causality, and that obesity leads to a reduction in physical activity."

However the data are consistent with the idea that brief bursts of vigorous physical activity on a daily basis--running around, playing soccer--increased calorie output enough to lower the risk of obesity in children. Total physical activity (which included more leisurely exercise) was not as important as moderate to vigorous activity.

Naturally, most press accounts emphasized the word "brief" in their reports. But as the study makes clear, the more active the children were, the less likely they were to have trouble with their weight.

Bottom line: Kids still have to eat healthfully--calorie intake being the other half of the weight equation--but physical activity should not be overlooked.

Update: See also my post from April 20, 2007 that helps you determine the difference between moderate and vigorous excerise.

Source: Ness AR, Leary SD, Mattocks C, Blair SN, Reilly JJ, et al. (2007) Objectively Measured Physical Activity and Fat Mass in a Large Cohort of Children. PLoS Med 4(3): e97v doi:10.1371/journal.pmed.0040097