Lack of exercise 'does not cause childhood obesity'

The modern stereotype of a childhood spent playing video games and being driven to and from school is often blamed for the rise in obesity among the UK's children. But a new study from the Peninsula Medical School in Plymouth has suggested that children reduce their activity levels because they become overweight, rather than the other way around.

A previous study found that programmes to reduce children's weight by increasing physical activity led to an average weight loss of just 90g. So the Plymouth researchers decided to investigate this link in more detail.

The Early Bird research program has been following a group of children for the past 11 years so the researchers used this data to find out if lack of activity comes before weight gain, or vice-versa.

Results of the study

The researchers analysis found that weight gain was followed by a reduction in physical exercise, but changes in activity levels had no impact on a child's weight.

An increase in body weight of 10 per cent led to a reduction in activity of four minutes less exercise per day for a 7 year-old child, they said.

While this reduction does not seem like a great deal, the study authors claim that it adds up to a significant impact over time. Lead author Terry Wilkin explains: "Moderate and physical activity only occupies in boys a little less than an hour a day and in girls about 45 minutes. So it's a not insubstantial amount of activity that is gained by having the lower body mass."

"And that of course is energy expenditure day in day out, week in week out, month in month out so the balance is changed substantially" he added.

Obesity begins at home

Becoming overweight may make children more conscious of their body and therefore less willing to become involved in physical activities such as sport. The extra weight may also make them more uncomfortable when exercising, reducing their incentive to continue.

In fact weight gain in children starts before they begin school. The strongest predictor of being obese is having an obese parent of the same sex (i.e. girls with obese mothers and boys with obese fathers are most likely to be obese themselves).

Published in the Archives of Disease in Childhood, this research suggests that health campaigners would be better off focussing on eating habits in younger children rather than trying to encourage more exercise in already overweight children as a means of reducing the overall health of our children.

Other viewpoints

Others have challenged the findings, pointing out that exercise delivers more health benefits than just reducing weight, and that children should continue to be encouraged to exercise more despite these findings.

A spokesman for the Department of Health commented "We will consider this evidence alongside other research which has different findings on the link between physical activity and weight when we are developing our policy to produce better public health outcomes."

This article was published on Thu 8 July 2010