Prevalence of overweight and obese children between 1989 and 1998: population based series of cross sectional studies.

OBJECTIVE To determine trends in weight, height, and body mass index in children between 1989 and 1998. DESIGN Retrospective series of cross sectional studies of routinely collected data. SETTING Primary care in the Wirral Health Authority. PARTICIPANTS 35 662 infants aged 1-3 months (representing 88% of live births) and 28 768 children aged 2.9-4.0 years. 21 582 infants and children (25.1%) were excluded because of missing or inaccurate data. MAIN OUTCOME MEASURES Weight, height, sex, and age routinely recorded by health visitors. Height, weight, and body mass index standardised for age and sex. SD score >1.04 for body mass index (>85th centile) was defined as overweight and >1.64 (>95th centile) as obese. Body mass index was not calculated in infants as it is difficult to interpret. RESULTS From 1989 to 1998 there was a highly significant increasing trend in the proportion of overweight children (14.7% to 23.6%; P<0.001) and obese children (5.4% to 9.2%; P<0.001). There was also a highly significant increasing trend in the mean SD score for weight (0.05 to 0.29; P<0.001) and body mass index (-0.15 to 0.31; P<0.001) but not height. Infants showed a small but significantly increasing trend in mean SD score for weight (-0.17 to -0.05; P=0.005). CONCLUSIONS From 1989 to 1998 there was a highly significant increase in weight and body mass index in children under 4 years of age. Routinely collected data are valuable in identifying anthropometric trends in populations.