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Abstract
Objective To compare changes in BMI and waist circumference in the past 30 years among English children aged 11–16 years.
Design Cross-sectional health examination surveys.
Setting The Health Survey for England (HSE) is a survey of a random sample of the general population living in private households in England.
Participants A new, nationally representative sample is selected each year. 1988 children aged 11–16 years had a nurse visit in the three HSE years 2005–2007, of whom 1770 had valid waist circumference measurements. HSE data were compared with age-specific centile charts for waist circumference for British children aged 5.0–16.9 years derived from baseline surveys of 3585 boys in 1977 and 4770 girls in 1987.
Main outcome measures BMI and waist circumference z-scores derived from the baseline data, as BMI and waist circumference vary by age and sex.
Results The mean z-scores for waist circumference for children aged 11–16 years in 2005–2007 was substantially higher than the mean z-score for BMI, for both sexes: WC 1.0 (95% CI 0.93 to 1.1), BMI 0.54 (0.44 to 0.63) for boys; WC 1.3 (1.2 to 1.4), BMI 0.48 (0.40 to 0.56) for girls (both p<0.001). There were no significant differences by sex in mean z-score for BMI, weight or height but the mean waist z-score for girls was significantly higher than that for boys (p<0.001). There were no significant differences by age in waist circumference or BMI. All children except for those in the lowest decile of waist circumference for girls had an increase in waist circumference of at least +1 SD since the 1977/87 baseline. BMI z-score increased across the top nine deciles of the BMI distribution by 0.4SD (2nd to 4th deciles) to 0.9SD (top decile). There were no significant differences by sex in the change over time except for the 10% of girls with the largest waist circumference for their age (1.6SD in girls vs 1.4SD in boys, p<0.01).
Conclusion Waist circumference in adolescents has increased more than BMI, which may result in greater obesity-related adverse health impacts in the future. The increase in waist circumference has been greater for girls than for boys. Increases in the mean z-score across the majority of the population suggests that the whole population is becoming more obese, although this effect is more pronounced at the upper end of the distribution.