Fat Mass Influences Femur Bone Strength and Geometry Parameters, but Not Bone Mineral Density, in Autoimmune Diabetes: A Pilot Study

Background Autoimmune diabetes (AD) increases fracture risk. Overweight worsens bone health despite increasing bone mineral density (BMD). This study examines how adiposity influences BMD and Dual X-Ray Absorptiometry (DXA)-derived parameters of bone geometry and strength in AD.Methods DXA scan was used to assess body mass composition, BMD, trabecular bone score (TBS), and hip structural analysis (HSA)-derived parameters at narrow neck (NN), intertrochanteric (IT) and femur shaft (FS) in 52 normal weight adults with AD and 51 with AD and overweight. Multilinear regression models were used to adjust the associations for age, sex, BMI, HbA1c%, lean mass % and physical activity.Results Total Fat% was negatively associated with markers of bone strength and geometry at different femur sites, including cross-sectional moment of inertia (CSMI) and section modulus (Z) at IT site, cross-sectional area (CSA), CSMI and Z at the FS site and CSMI, buckling ratio (BR) and Z at the NN site, after adjustment for confounders. Visceral adipose tissue emerged as a negative independent predictor of BR at IT and NN. Lean mass % was positively associated with TBS, CSA, CSMI and Z at the IT and FS sites. Negative predictors of bone health were female sex and age.Conclusion In adults with AD, excess fat mass, including visceral adiposity, is independently associated with impaired hip bone strength and geometry at the femur shaft. These findings highlight the limitations of BMD alone in evaluating bone health in people with AD and overweight, emphasising the negative skeletal effects of adiposity.