The rise and the recent decline of childhood obesity in Swedish boys: the BEST cohort.

BACKGROUND/OBJECTIVES: Childhood obesity increases the risk for adult obesity and diseases. The aim of this study was to investigate secular changes of childhood body mass index (BMI), overweight and obesity in boys born during 1946-2006, using the population-based BMI Epidemiology STudy (BEST) cohort in Gothenburg, Sweden.

SUBJECTS/METHODS: We collected height and weight from archived school health records for boys born every 5 years 1946-2006 (birth cohort 1946 n=1584, each birth cohort 1951-2006 n=425). Childhood BMI at 8 years of age was obtained for all the participants.

RESULTS

Childhood BMI increased 0.18 kg m (95% confidence interval: 0.16-0.20) per decade increase in birth year, during 1946-2006. The increase was significant from birth year 1971, peaked 1991 and was then followed by a stabilization or tendency to a reduction. Next, we aimed to thoroughly explore the trend after birth year 1991 and therefore expanded birth cohorts 1991 (n=1566), 2001 (n=6478) and 2006 (n=6515). Importantly, decreases in mean BMI (P<0.01), prevalences of overweight (P<0.01) and obesity (P<0.05) were observed after birth year 1991. For boys born in Sweden and with parents born in Sweden, a substantial reduction in the prevalences of overweight (-28.6%, P<0.001) and obesity (-44.3%, P<0.001) were observed between birth year 1991 and birth year 2006.

CONCLUSIONS

This long-term study captures both the rise and the recent decline of childhood obesity. As childhood obesity is strongly associated with subsequent adult obesity, we anticipate a similar reduction in adult obesity during the coming decades in Swedish men.