3. Measurement of bone density and body composition by DXA

Anthropometric data, including weight, height, and body mass index, were assessed during the first visit. All participants underwent DXA (Discovery-W fan-beam densitometer; Hologic Inc., Waltham, MA, USA) to assess BMD and body composition without specific preparation. Their BMD was measured at the lumbar spine (L1–L4), the femoral neck, and the total femur, and the resulting value was expressed in g/cm². The least significant change (LSC) was also computed to determine if BMD changes were significant (95% confidence interval). The LSC of the total femur and the lumbar spine are 0.027 g/cm² and 0.022 g/cm², respectively.

Body fat, LBM, total body mass, and specific region mass, such as the arm, leg, trunk, head, android region, and gynoid region, were measured using DXA. The Hologic Apex software (13.6.05) used in the scan analysis defined the android and gynoid regions. The android region is found around the waist, located between the lumbar spine’s midpoint and the pelvis’s top. Meanwhile, the gynoid region is found between the femur head and the middle of the thigh.[⁷] Appendicular skeletal muscle mass was calculated as the sum of muscle mass in the arms and legs, assuming that all non-fat and non-bone tissues are skeletal muscle. Skeletal muscle mass index (SMI) was calculated by dividing the limb skeletal muscle mass (kg) by the square of the height (m²).