It is well recognised that bariatric (weight loss) surgery can harm bones. Bone mineral density can suffer because of changes in calcium and vitamin D metabolism. The section on What is the risk to the health of bones after bariatric surgery? in my website gives a simple outline of calcium and vitamin D physiology. Nutritional guidelines from the British Obesity and Metabolic Surgeons Society explain the necessary care for bone health.
A recently published study in the British Medical Journal highlights the increase risk for fractures after bariatric surgery. Also, the pattern of fractures is different before and after bariatric surgery. Before surgery, obese people have increased risk for distal lower limb fractures (fractures below the knee) than non-obese people. After surgery, the risk of below knee factures is halved. But, the proportion of fractures of the hip, pelvis and femur (thigh bone) is tripled! Also, the risk for arm fractures is increased. This change in the distribution of fractures can be explained by osteoporosis. Fractures after bariatric surgery occur in the sites that are most prone to loss of bone mineral density (osteoporosis).
There are some limitations in this study, and further research is needed. But, one message is clear: we should emphasize attention to bone health after bariatric surgery.