It has been known for some time that overweight children are less active than their normal weight counterparts. But it's been hard to show which comes first, the extra weight or the lower activity. A three-year study of British children suggests that being overweight lowers activity, but the amount of a child's activity does not influence weight gain or loss.
The implications of the study are obvious: The childhood obesity epidemic will not be solved through exercise.
EarlyBird is a study of 307 schoolchildren in Plymouth, UK that has been ongoing since 2000. All the children in the study have a range of measurements, including physical activity and body fat, taken once a year.
The EarlyBird study suggests that effectively tackling childhood obesity requires focusing on what and how much children are eating.
The more body fat children had at age seven, the less active they were over the next three years. But the amount of physical activity at age seven had no effect on the amount of body fat at age ten. Taken together, these results suggest that being overweight appears to be the cause of inactivity, not a result of it.
This isn't a license to avoid exercise. The many and varied health benefits of exercise are well known. It merely suggests that lack of exercise is not why people get fat in the first place.
The EarlyBird study is only a single study of a few hundred children. But it does have some backing from other studies. A 2009 analysis of several studies using physical activity as a tool to reduce childhood obesity showed an average weight loss of just 90 grams (3 oz.) over three years. Together, they add up to the simple idea that obesity comes from food.
Overweight children tend to become overweight adults. The EarlyBird study suggests that effectively tackling childhood obesity requires focusing on what and how much children are eating.