Growing up before growing out: secular trends in height, weight and obesity in 5--6-year-old children born between 1970 and 2006.

BACKGROUND: This was a whole-population study of height, weight and obesity prevalence in 5-6-year-old children born between 1970 and 2006 in the Grampian region, north east Scotland.
METHODS: Heights and weights collected as part of routine primary school medical entry were obtained from different sources. Obesity was defined as body mass index (BMI)≥98th centile.
RESULTS: Anthropometric measurements were made in 194391 children, mean age 5.6 years (SD 0.8). The mean height z scores rose for those born between 1970-2000 respectively and were static thereafter. Obesity prevalence was non-linear over time and initially fell for birth years 1970-1977, rising between 1977 and 1998 before falling for those born between 1998 and 2006. For the whole population, the prevalence of obesity rose from 1.3% for those born in 1976 to 6.9% for those born in 1998 and fell back to 5.7% for children born in 2006. Obesity was initially highest in girls and most affluent communities but became most prevalent among boys and least affluent communities.
CONCLUSIONS: The secular increase in height at school entry in children born in 1970 and afterwards was followed by an increase in weight leading to an initial reduction in obesity prevalence. Whole-population obesity prevalence for children born in the 2000s is now falling but prevalence remains considerably higher compared with those born in the 1970s. Obesity prevalence continues to rise among less affluent communities.