Relationship of upper body fat distribution to higher regional lean mass and bone mineral density

We investigated the relationship of upper body fat distribution to regional bone mineral density (BMD). Subjects were 361 regularly menstruating premenopausal women with right-side dominance. Age, height, and weight were recorded. Regional (arms, L2–L4 of the lumbar spine, and legs) BMD, regional (arms, trunk, and legs) lean mass, and the ratio of trunk fat mass to leg fat mass amount (trunk–leg fat ratio) were measured by dual-energy X-ray absorptiometry. Body fat distribution was assessed by trunk–leg fat ratio. Trunk–leg fat ratio was positively correlated with regional BMD (r = 0.120–0.216; P < 0.05–P < 0.001) and regional lean mass (r = 0.162–0.229; P < 0.01–P < 0.001). Regional lean mass was more positively correlated with regional BMD (r = 0.319–0.475; P < 0.001). These relationships remained significant after adjusting for age and height. However, correlation of trunk–leg fat ratio with regional BMD disappeared after additionally adjusting for regional lean mass. In premenopausal women, upper body fat distribution is associated with higher regional BMD via greater regional lean mass irrespective of age and height.