Low levels of physical activity in 5-year-old children.

As the prevalence of obesity in Western societies has increased to disturbing levels, interest in the role of physical inactivity in promoting this trend has increased. We assessed physical activity energy expenditure (AEE) in 127 5-year-old children, 43 of whom were white children and 84 Pima Indian children; the latter group represents a population with an extremely high prevalence of obesity. Total energy expenditure (TEE) and resting metabolic rate (RMR) were measured by the doubly labeled water method and indirect calorimetry, respectively. From these measured values, different indexes of physical activity were calculated, including AEE = TEE-(RMR + 0.1 x TEE) and physical activity level (PAL = TEE/RMR). By the age of 5 years, Pima Indian children were significantly heavier (23.0 +/- 5.3 kg vs 19.1 +/- 2.6 kg) and fatter (30 +/- 7% vs 21 +/- 5% body fat) than white children (p < 0.0001), whereas TEE (5996 +/- 1005 kJ/day vs 5690 +/- 760 kJ/day) and RMR (4431 +/- 625 kJ/day vs 4236 +/- 534 kJ/day) were similar in the 2 groups in both absolute values and after adjustment for fat-free mass, fat mass, and sex. Both white and Pima Indian children had physical activity levels 20% to 30% lower (PAL = 1.35 +/- 0.13) than currently recommended by the World Health Organization (1.7 to 2.0). However, the different calculated indexes of physical activity were comparable in the two racial groups. Differences in TEE or AEE are unlikely to explain the obesity seen in Pima Indian children at a later age, suggesting that excess food intake is likely to play a major role in the cause of obesity in this obesity-prone population. However, both white and Pima Indian children have surprisingly low levels of physical activity, a condition that portends poorly for the prevention of obesity in adulthood.