Children’s Exercise Interventions Show Negligible Impact on Obesity
Interventions such as additional exercise classes appear to have only a minor effect on the rising problem of obesity amongst children, according to a recent review published in the British Medical Journal.
A plethora of previous research has confirmed that the more physically active children are the more they are likely to be of a healthy weight (as measured by BMI) and furthermore the more likely they are to remain active and maintain a healthy weight into adulthood.
Not surprisingly this has led to the development of interventions aimed at increasing levels of physical activity in children by providing them with extra exercise sessions during or after school.
However according to the review these interventions have only a negligible effect on improving children's BMI.
Measuring Daily Activity – Only ‘Hard Data’ Included
Researchers from Plymouth and Exeter Universities carried out a systematic review of studies. What made this review distinct was that they did not rely on data from questionnaires, but used "hard" measures of actual physical activity obtained from accelerometry devices. The study also took into account whole day activity, or total bodily movement across waking hours.
For the purpose of the review, the authors used only databases and references lists for peer-reviewed journal studies. Furthermore the interventions included in the review had to have been designed to increase activity levels in children under 16, must have been observed for at least four weeks and measured results objectively using accelerometers.
30 randomized controlled trials that took place between January 1990 and March 2012 matched these requirements. All the studies were matched on age, ethnicity, and socio-economic status, and the results were adjusted for gender and activity levels at the start of the intervention period.
Eight of the studies had included only overweight or obese children, while the rest included children from all BMI ranges.
The researchers assessed the effect of interventions on total physical activity and time spent on moderate or vigorous physical activity.
Small to Negligible Effects
Following the review the research team concluded that the interventions had a "small-to-negligible" impact: there was little increase in total activity volume and only a small increase in time spent in moderate or vigorous intensity activity (about the same as four minutes of walking or running per day).
Such tiny improvements in physical activity levels would not be sufficient to make significant reductions in children's BMI or body fat.
Previous studies have suggested such interventions don't achieve reductions in BMI and body fat because they make children eat more calories.
The authors suggest another reason for the failure to impact BMI: the interventions could be displacing equally active periods, such as after-school clubs, which would usually take place outdoors.
While it is understandable for us to jump to the conclusion that the answer to the obesity crisis in kids is to make them do more exercise, the authors suggest we think carefully first, and urge future studies to take into account the effect of any interventions on whole day activity as well as activity-specific periods, as "small increase gained from formal interventions seems insufficient to improve the body mass / fat of children."