Abstract
Objective. Early adiposity rebound ([AR], when body mass index [BMI] rises after reaching a nadir) strongly predicts later obesity. We investigated whether the upswing in BMI at AR is accompanied by an increase in body fat. Design. Community-based cohort study. Subjects. A total of 299 first-born children (49% male). Measurements. Six-monthly anthropometry and bioelectrical impedance, 4–6.5 years; lean and fat mass index (kg/m2) for direct comparison with BMI. Supplementary (0–2 years) weight and length measures (needed for growth curve modelling) were drawn from subjects’ child health records. Methods. AR was estimated from individually modelled BMI curves from birth to 6.5 years. Two main analyses were performed: 1) cross-sectional comparisons of BMI, fat mass index (FMI), lean mass index (LMI) and percent body fat in children with early (<5 years) and later (>5 years) rebound; and 2) investigation of linear trends in BMI, FMI, LMI and percent body fat before and after AR. Results. The 81 children (27%) experiencing early AR had higher BMI, FMI, LMI and percent fat at 6.5 years. Overall, FMI decreased steeply pre-AR, at −0.56 (0.02) kg/m2 per year (mean [Standard Error]), then flattened post-AR to 0.07 (0.05) kg/m2 per year. In contrast, LMI increased pre-AR (0.34 [0.01]) and steepened post-AR (0.47 [0.03] kg/m2 per year). Conclusion. The ‘adiposity rebound’ is characterised by increasing lean mass index, coupled with cessation of the decline in fat mass index. Understanding what controls the dynamics of childhood body composition and mechanisms that delay AR could help prevent obesity.
Acknowledgments
The PEAS Kids Growth Study was funded by the Murdoch Childrens Research Institute seed funding and NHMRC project grant #284582. The authors’ work was independent of the funders (the funding source had no involvement). MW was supported by NHMRC Population Health Career Development Awards #284556 and #546405, and MC by NHMRC Public Health Capacity Building Grant #436914.
We would like to acknowledge the past contributions of Susie Gallagher and Louise Canterford. We thank all the research staff, Maternal & Child Health Nurses and families involved in the PEAS Program and PEAS Kids Growth Study.
We declare that there are no competing financial interests in relation to the subject matter or materials described in this manuscript. The PEAS Kids Growth Study was funded by the Murdoch Childrens Research Institute seed funding and NHMRC project grant #284582. The authors’ work was independent of the funders (the funding source had no involvement). MW was supported by NHMRC Population Health Career Development Awards #284556 and #546405, and MC by NHMRC Public Health Capacity Building Grant #436914.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.