Trends in body mass index in young adults in England and Scotland from 1973 to 1988.

STUDY OBJECTIVE The aim was to determine whether the mean body mass index of young adults in England and Scotland had increased during the years 1973 to 1988. DESIGN The study was an analysis of reported heights and weights for parents of children participating in a mixed longitudinal study of children's growth. SETTING 20 study areas (16 in England and four in Scotland) were selected by stratified random sampling. SUBJECTS Subjects were parents of 5229 children who were new entrants to the study in the years 1973-6 and 1982-8. After excluding cases containing missing values on continuous variables, data for 4568 (87%) women (mean age 30 years) and 4029 (77%) men (mean age approximately 32 years) were analyzed. MEASUREMENTS AND MAIN RESULTS Changes in weight for height over time were determined using body mass index as dependent variable, adjusting for age, social class, family size, and study area. In women, mean body mass index showed an annual increase of 0.10 (95% CI 0.03 to 0.17%) per year of study. Body mass index also increased with increasing age and family size and was greatest for women with husbands in manual occupations. The secular trend in body mass index in women was not explained by changes in the distribution of these variables. The proportion of women with BMI greater than 25 kg/m2 increased over the study period. In men the secular trend in body mass index was not quite significant in this age group [annual increase 0.05% (-0.01 to 0.12%)]. CONCLUSIONS There has been an increase in the body mass index of young women in England and Scotland over the years 1973 to 1988. This increase was not explained by changes in the age, parity, social class of the subjects sampled. Evidence of a trend in men was not found.