Weight loss surgery can increase the risk of bone loss

New studies show patients continue to lose bone even two years after weight loss surgery; patients’ bone health should be monitored and nutritional supplements prescribed.

It is no secret that obesity is on the increase and reaching epidemic levels in many countries.

According to the World Health Organization (WHO) more than 10% of the world’s adult population was obese in 1980 and obesity has since more than doubled. In the USA, the Centers for Disease Control and Prevention estimate that more than one-third of the adult population is obese. Not surprisingly, hospitals have seen a large increase in the number of bariatric surgeries performed.

What is bariatric surgery?

Bariatric surgery (also known simply as weight loss surgery) is a procedure that helps people to lose weight. Ranging from gastric bypass to gastric banding, the different types of bariatric surgery aim to restrict food intake and decrease the absorption of food in the stomach and intestines.

The surgical route is often an option of last resort, when pharmacologic and dietary measures have already failed and the patient is at high-risk of obesity-related health issues. However, although bariatric surgery is undisputedly one of the most effective long-term medical solutions for weight loss, it is also accompanied by significant biochemical, hormonal and mechanical changes in the body.

Obese people are at higher risk of chronic vitamin D deficiency and inadequate calcium intake to begin with - following bariatric surgery, they are at even higher risk, due to decreased oral intake and malabsorption, in which the intestine's ability to absorb important nutrients is affected. This raises concern about compromised bone health and increased risk of osteoporosis.

In fact, various research has shown that weight loss surgery may have an impact on the skeleton, such as bone loss and increased fracture risk. One recent study found that within a group of 258 severely obese bariatric surgery patients with an average body mass index (BMI) of 49 kg/m2 there was a two-fold increased risk of fractures at the hip, spine and wrist as well as a 2.3-fold increased risk at other sites.1 BMI is a measure of body fat based on height and weight that applies to adult men and women, with the normal range being 18.5-24.9 kg/m2. Although fracture rates appeared increased in the bariatric surgery patients, it is worth noting that rates in these patients were compared with those in the general population, and rates were not assessed in similar individuals who did not undergo surgery. Interestingly, in an earlier paper of a much larger population from the UK, in which bariatric surgery patients were matched to control subjects of similar BMI, there appeared to be no increased fracture risk over the 1st few years, but a suggestion of a potentially increased risk at around 5 years. Clearly further studies will be needed to definitively confirm that bariatric surgery in itself predisposes individuals to fracture. However, these recent studies suggest that bone health should be considered as part of overall care of these patients. 

Various other studies have also shown evidence of calcium and vitamin D deficiency as well increased bone loss. The latest study by investigators at the Massachusetts General Hospital in Boston has found that patients who have had gastric bypass surgery (a form of bariatric surgery) not only have a high rate of bone loss in the first year after surgery, but that the bone loss persists two years after surgery, even after the patients’ weight stabilizes.

Pay attention to bone health before and after surgery

Experts therefore recommend that prior to surgery the patient’s bone health be assessed, with attention also given to risk factors for osteoporosis.3 After the surgery, patients should ensure that they take the necessary mineral and vitamin supplements, including calcium and vitamin D, and that the absorption of the key nutrients is monitored. Patients at risk need to be considered for bone density testing and be prescribed osteoporosis therapy if needed.

IOF CEO Judy Stenmark stated,

Severely obese people worldwide are now benefiting from new and improved methods of weight loss surgery. It is therefore important that both doctors and patients are aware of the potential impact of the surgery on bone health. Early preventive action needs to be taken so that patients can enjoy the health and lifestyle benefits that result from weight loss, without the threat of disability due to osteoporotic fractures.”

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