Trim the gut, lose the weight - and the bone.

Vertical sleeve gastrectomy (VSG) is an effective therapeutic approach for obesity and type 2 diabetes but is associated with osteoporosis. In this issue of the JCI, Li et al. report that VSG rapidly reduces bone mass, as observed in humans, via rapid demineralization and decreased bone formation, independent of weight loss or Ca2+/vitamin D deficiency. VSG also reduces bone marrow adipose tissue, in part via increased granulocyte-colony stimulating factor (G-CSF). The interplay between VSG-mediated effects on systemic metabolism and bone biology remain to be investigated. These findings suggest novel mechanisms and therapeutic targets for bariatric surgery-induced osteoporosis.