Questioning Government Guidelines For Childhood Physical Activity And The Association With Childhood Obesity

Main Category: Obesity / Weight Loss / Fitness
Also Included In: Pediatrics / Children's Health
Article Date: 03 Jul 2008 - 2:00 PST

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A longitudinal study of childhood physical activity at the Government-recommended level and obesity-related health outcomes questions the value of UK and US government guidelines and the use of BMI as the outcome measure.

The study carried out by the EarlyBird Diabetes Research Centre at the Peninsula Medical School in Plymouth aimed to determine the extent to which physical activity at the Government-recommended intensity is associated with change in body mass/fat and metabolic health in pre-pubertal children.

In this non-intervention longitudinal study of 113 boys and 99 girls (born 1995-96) recruited from 54 local schools, physical activity (MTI accelerometers), changes in body mass (raw and age/gender-standardized BMI), fatness (skin-fold thickness and waist circumference) and metabolic status (insulin resistance, triglycerides, cholesterol/HDL ratio and blood pressure - separately and combined as a composite metabolic score) were measured on four annual occasions (5, 6, 7 and 8y).

Results showed that mean physical activity did not change over time in either sex. Averaging the seven-day recordnigs from four time-points rather than one increased the reliability of characterising a child's activity from 71% to 90%. Some 42% of boys and 11% of girls met the guideline.

There were no associations between physical activity and changes in any measure of body mass or fatness over time in either sex (e.g. BMI-SDS: r=-0.02, p=0.76). However, there was a small-to-moderate inverse association between physical activity and change in composite metabolic score (r=-0.19, p<0.01). Mixed effects modeling showed that the improvement in metabolic score among the more active compared to the less active children was linear with time (-0.08 z-scores/year, p=0.001).

Although physical activity in children above the Government-recommended intensity of 3 METs is associated with a progressive improvement in metabolic health, it is not associated with a change in BMI or fatness (though direction of causality is not certain). Girls habitually undertake less physical activity than boys, questioning whether girls in particular should be encouraged to do more, or if the recommendations should be adjusted for girls.

PENINSULA MEDICAL SCHOOL
Tamar Science Park
Davy Road
Plymouth
PL6 8BX
http://www.pms.ac.uk