Aims: The long-term relationship of fatness during growth and bone health in adulthood is uncertain. We aimed to determine associations between fat mass (FM) and overweight/obesity status at different stages of growth with bone measures in early adulthood.
Methods: A birth cohort followed at ages 8, 16 and 25 years (n=201). At age 25 years, lumbar spine, hip and total body bone mineral density (aBMD) were measured by DXA, and trabecular, cortical volumetric BMD (vBMD) and microarchitecture at the distal radius and tibia were measured by HRpQCT. Multivariable linear regression was used to examine associations of FM (by DXA/skin fold), body mass index (BMI) at ages 8, 16 and 25 years and change in overweight/obesity status (BMI ≥85th percentile on CDC growth charts/>25 kg/m2) from 8 to 25 years with bone outcomes at age 25 years. FM, BMI and bone outcomes were standardised, i.e. coefficients give SD change in outcome per SD of exposure.
Results: The prevalence of overweight/obesity was 18%, 25% and 55% at ages 8, 16 and 25, respectively. FM had beneficial associations with cortical vBMD, cortical porosity (at ages 8 and 25), and trabecular number (at ages 16 and 25) at radius and tibia (β=-0.24 to 0.31) but no associations with aBMD. Higher BMI and persistent overweight/obesity from age 8 to 25 years were associated with higher aBMD (BMI: β=0.18 to 0.31; overweight: β=0.58 to 0.73), higher cortical thickness, greater trabecular number, less separation but thinner trabecular bone (BMI: β=-0.32 to 0.42; overweight: β=-0.54 to 0.97) at radius and/or tibia; they were not associated with vBMD.
Conclusions: Higher FM and overweight/obesity in childhood and early adulthood may be beneficial for bone at the age of peak bone mass. However, this should be weighed against the proven detrimental effect of obesity on other health outcomes.