Predicting obesity in early adulthood from childhood and parental obesity.

Objective: To determine the degree of tracking of adiposity from childhood to early adulthood, and the risk of overweight in early adulthood associated with overweight in childhood and parental weight status in a cohort of children born in the mid-1970s.

Design: Longitudinal observational study.

Subjects: Approximately 155 healthy boys and girls born in Adelaide, South Australia, 1975-1976 and their parents.

Measurements: Height and weight of subjects at 2 y, annually from 4 to 8 y, biennially from 11 to 15 y and at 20 y, and of parents when subjects were aged 8 y. Body mass index (BMI) of subjects converted to standard deviation scores and prevalence of overweight and obesity determined using worldwide definitions. Parents classified as overweight if BMI> or =25 kg/m(2). Tracking estimated as Pearson's correlation coefficient. Risk ratio used to describe the association between weight status at each age and parental weight status and weight status at 20 y and weight status at each earlier age, both unadjusted and adjusted for parental weight status.

Results: The prevalence of overweight/obesity increased with age and was higher than that reported in international reference populations. Tracking of BMI was established from 6 y onwards to 20 y at r-values >0.6, suggesting that BMI from 6 y is a good indicator of later BMI. Tracking was stronger for shorter intervals and for those subjects with both parents overweight compared with those with only one or neither parent overweight. Weight status at an earlier age was a more important predictor of weight status at 20 y than parental weight status, and risk of overweight at 20 y increased further with increasing weight status of parents.

Conclusion: Strategies for prevention of overweight and targeted interventions for prevention of the progression of overweight to obesity are urgently required in school-aged children in order to stem the epidemic of overweight in the adult population.