Longitudinal modelling of body mass index from birth to 14 years.

BACKGROUND

To examine the tracking of BMI from birth to age 14 years.

PARTICIPANTS AND METHODS

Linear mixed model (LMM) analysis was used to model the trajectories of BMI (n = 1,403). Adiposity rebound was investigated for a subset of individuals (n = 173).

RESULTS

Adolescents who were overweight or obese at 14 years followed a different BMI trajectory from birth compared to those of normal weight. There was a difference between weight status groups for the timing of adiposity rebound (p < 0.001) and BMI at nadir (p < 0.001). The LMM depicted a significant difference in rate of change of BMI over time for males and females (p < 0.001), with female BMI increasing at a faster rate, and for weight status groups (p < 0.005), with the obese cohort having the faster increase in BMI over time. BMI at birth was significantly lower for the normal weight cohort compared to the overweight (p = 0.029) and obese (p = 0.019) cohorts.

CONCLUSION

This study introduces a powerful analytic tool, LMM, to model BMI and shows that weight status at 14 years is the result of a distinct path in earlier years. Compared to their normal weight peers, overweight and obese adolescents experience an earlier adiposity rebound, with a higher BMI at rebound.