Increasing prevalence of obesity in primary school children: cohort study

From 1996 to 1999 an auxologist (JW) measured children in 10 primary schools in Leeds participating in a health promotion programme.3 Children in years 3 and 4 (age 7-9 years) were measured in July 1996 and again in July 1997 and 1998. These children were marginally more advantaged than average for Leeds, with 1-42% of pupils from ethnic minorities and 7-29% entitled to free school meals (a measure of social disadvantage). Height was measured to 0.1 cm with a free standing Magnimeter stadiometer (Raven, Dunmow). Weights were recorded to 0.1 kg without shoes or jumpers. The mean of three triceps measurements was taken.4 Body mass index (weight (kg)/(height (m)2)) was calculated and converted to standard deviation scores using the revised 1990 reference standards5 and the Tanner Whitehouse (1975) standards for skinfold thickness.4 The following conventional cut-off points were applied: body mass index standard deviation score greater than 1.04 (85th centile) for overweight and greater than 1.64 (95th centile) for obesity. Using these definitions the expected percentages were 15% for overweight and 5% for obesity, relative to British children in 1990. Observed levels were compared with expected levels using χ2 goodness of fit test. All but 21 children agreed to participate. Overall, 608 children were measured in 1996, 540 in 1997, and 499 in 1998 (some of whom were not measured in 1997). In addition 86 new children joined the study in 1997 and 1998. In total 694 children were measured, resulting in 1762 measurements. The table shows the proportion of children with body mass index and triceps measurements above the 85th and 95th centiles according to age. A significant increase in the proportion of overweight and obese children was observed in those aged 9, 10, and 11 years.