Determinants of Adiposity Rebound Timing in Children

Abstract

Objective: Adiposity rebound (AR) or BMI (body mass index) rebound refers to the increase in BMI following the minimum BMI in early childhood. Early AR (before age 5) is predictive of adult obesity. To determine how 4 domains - demographics, maternal BMI, food security, and behavioral characteristics - may affect timing of AR.

Study design: A total of 248 children, ages 2.5-3.5 years, in Latino farmworker families in North Carolina were examined at baseline and every 3 months for 2 years. BMI was plotted serially for each child and the onset of BMI rebound was determined by visual inspection of the graphs. Given the ages of the children, all rebounds were detected before age 5 years and were deemed "early," whereas other children were classified as "nonrebounders." Classes were then compared in terms of the 4 domains with the use of bivariate analyses and linear mixed models.

Results: A total of 131 children demonstrated early rebound, 59 children were nonrebounders, and a further 35 had inconclusive data. Parents of early rebounders were less likely to have documentation permitting legal residence in the US. Mothers of early rebounders were on average 3 BMI units heavier. Sex, household food security, diet quality, caloric intake, and daily activity did not differ between classes. In multivariable analysis, female sex, limited maternal education, increased maternal BMI, and increased caloric intake were significant predictors of early rebound.

Conclusion: High maternal BMI was the strongest predictor of early BMI rebound, but increased caloric intake also was significant. Limiting excess calories could delay premature AR and lower the risk of future obesity.

Keywords: Latino farmworker families; childhood obesity; determinants of adiposity rebound timing; diet; early adiposity rebound; food security; maternal body mass index; physical activity.

Figure 1: online

Four representative growth trajectories. Panel A is representative of very early rebounders, with minimum body mass index (BMI) before the age of 3.5 years and steady increase thereafter. Panel B demonstrates early rebound (between the ages of 3.5 and 5 years), with minimum BMI at around 4.5 years followed by an increase. Any increase after the adiposity rebound (AR) must be at least 0.2 BMI units per year. Panel C shows an individual who has not yet rebounded–there is no rise in BMI. Panel D shows data deemed inconclusive, because there is not sufficient data to indicate whether the point of minimum BMI constitutes the beginning of AR. Data was deemed inconclusive if there were either fewer than 4 total observation points or fewer than 2 observations after the BMI minimum. This step was taken to account for the possibility of measurement error and random fluctuation in BMI.

Figure 2

Longitudinal Change in Body Mass Index (BMI) and Weight-for-Age Percentile (WAPCT). BMI and WAPCT are shown for each class of children at baseline, the end of year 1, and the end of year 2.