Endocrine Abstracts

In general, higher body weight in adults is associated with higher bone mineral density and is protective against fracture, but may be associated with an increased risk of some fractures. Possible mechanisms for higher bone density include mechanostat response to increased loading and increased oestrogen production by adipocyte aromatase.

It has been increasingly recognised that bone interacts with other organs and tissues (such as fat, the gastrointestinal tract and the CNS), and also that fat is not just a passive energy reservoir but an endocrine organ with regulatory functions. Fat may have effects on bone through the actions of leptin in the CNS and directly on bone cells, and other adipokines such as adiponectin may also affect bone metabolism.

Subcutaneous and visceral fat may have differing effects on bone; visceral fat produces inflammatory cytokines which have pro-resorptive effects on bone, and higher visceral fat mass has been associated with increased bone turnover and lower bone density.

Intramuscular fat may also have effects on the skeleton, possibly through modulation of muscle loading.

There is generally an inverse relationship between bone density and the amount of bone marrow fat. It is not yet clear whether increased marrow fat contributes to the causation of osteoporosis, but models of osteoporosis with high marrow fat such as anorexia nervosa may offer insights into this relationship.

Understanding the inter-relationship of fat and bone can improve our understanding of the causes of osteoporosis and may offer new therapeutic targets.