Association of fat distribution with changes in bone outcomes in young girls

Abstract

BackgroundChildhood obesity may impair bone growth but the relationship remains unclear.ObjectiveExamine longitudinal associations between total body fat (TBF), android fat (AF), and skeletal muscle fat (SMF) content, with bone outcomes in 260 girls aged 8–13y.MethodsPeripheral quantitative computed tomography measured changes in bone strength index (BSI, mg2/mm4), strength‐strain index (SSI, mm3) and volumetric bone density (vBMD, mg/cm3) at distal metaphyseal and diaphyseal regions of the femur (fem) and tibia (tib), and baseline calf (CMD) and thigh (TMD) muscle density (mg/cm3), an index of SMF content. Baseline TBF and AF were assessed by dual‐energy X‐ray absorptiometry.ResultsTBF and AF were positively associated with fem BSI (r=0.193; r=0.174), tib SSI (r=0.184; r=0.142), and fem trabecular vBMD (r=0.196; r=0.203), and inversely associated with tib cortical vBMD (r= −0.146; r= −0.172). Lower CMD and TMD was associated with fem BSI (r= −0.222; r= −0.145), tib BSI (r= −0.193; r= −0.128), fem tot vBMD (r= −0.208; r= −0.168), and trabecular vBMD (fem: r= −0.263; r= −0.192, tib: r= −0.215; r= − 0.161). CMD was significantly associated with tib SSI (r= −0.141) and tot vBMD (r= −0.130). ANCOVA showed that girls in the middle thirds of TBF and AF had higher fem and tib cortical vBMD than girls with greater TBF and AF. Greater changes in fem BSI, tot fem vBMD and fem and tib trabecular vBMD were observed in the lowest vs. highest thirds of CMD and TMD. All results were significant at p<0.05.ConclusionsGains in TBF or AF may negatively impact tib bone development, while increases in CMD or TMD predict greater gains in various bone outcomes.Grant Funding Source: NIH/NICHD #HD‐050775