Bone Abstracts

Obesity is associated with greater risk of proximal humerus and ankle fracture, despite greater areal BMD (aBMD). We aimed to investigate whether greater risk of some fractures in obesity was due to skeletal or non-skeletal determinants. 100 individually-matched pairs of normal weight (NW) (18.5–24.9 kg/m²) and obese (OB) (BMI >30 kg/m²) individuals, aged 25–40 and 55–75 years underwent DXA to determine hip and lumbar spine aBMD, whole body lean mass (WBLM) and appendicular lean mass (ALM). We used HR-pQCT to determine volumetric BMD (vBMD) at the distal radius and tibia and micro-finite element analysis to estimate bone strength. Falls in the 6 months prior to recruitment were reported by questionnaire. Grip strength was measured with a dynometer. Short physical performance battery (SPPB) score was derived from gait speed, balance (from 6 m narrow walk), and repeated chair-stand time quartile. OB had greater hip and spine aBMD, tibia and radius vBMD (all P<0.001) and estimated failure load (Table 1). 15% of OB reported having fallen, compared to 5% of NW (P=0.07). OB had greater WBLM, ALM and skeletal muscle index (all P<0.001). Despite greater LM, SPPB score was poorer in OB, due to slower gait speed (P<0.001), slower chair-stand time (P<0.001) and poorer balance (P<0.01). There was no difference in grip strength between OB and NW. Obese individuals have higher BMD at all sites, so excess of some fractures in obesity may not be due to lower bone strength. Obesity appears protective against sarcopenia due to greater LM, but physical function is impaired. Poor physical performance in obesity could contribute to greater risk of falls and some fractures.