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"Excess body weight increases the load on the skeleton, and the high levels of leptin seen in obesity provide stimulation of bone formation," Dr. Torquati says. "This results in higher levels of bone density. However, the protective effect of high bone density on fracture risk is controversia l and very difficult to prove. More straightforward is to speculate that the benefit of sustained and significant weight loss can lead to less risk of fall-related injuries that are the ultimate cause for traumatic bone fracture." Intrigued by a spate of studies suggesting that bariatric surgery could contribute to bone density changes, Dr. Torquati and colleagues set out to investigate the longitudinal effect of surgical weight loss on real risk of fracture. "Our initial hypothesis was that, in bar- iatric surgery patients receiving adequate calcium and vitamin D supplementation, the risk of bone fracture was going to be similar to that observed in a matched population that did not undergo surgery," Dr. Torquati says. "Our study's hypothesis was confirmed by the results, including an expected lower odds of fracture in patients undergoing sleeve gastrectomy." SLEEVE GASTRECTOMY SUPERIOR TO GASTRIC BYPASS AT FRACTURE RISK REDUCTION Using Medicare records from 2004 to 2014, Torquati and colleagues separated 49,113 bar- iatric surgery-eligible patients into three groups of 16,371 individua ls each: a group of patients who did not undergo bariatric surgery, a group of patients who had under- gone Roux-en-Y gastric bypass and a group of patients who had undergone sleeve gastrec- tomy. Over a three-year period, fracture rates between the individua ls who did not have bariatric surgery and those who underwent gastric bypass were comparable, but people who underwent sleeve gastrectomy had much lower rates of fracture. For individua ls in the nonsurgica l and gastric bypass cohorts, the overall likelihood of experiencing a fracture was similar, as were the odds of fracture of the humerus, radius or ulna, pelvis, or vertebrae. Patients who underwent sleeve gastrectomy had a lower risk of fracture in all categories compared with individuals who did not have surgery, and a lower risk of total fracture and humeral fracture compared with patients who under- went gastric bypass. The sleeve gastrectomy and gastric bypass groups had similar odds of radius or ulna, hip, pelvis, or vertebrae fracture. The study was published in JAMA Network Open earlier this year. Gastric bypass effects weight loss, in part, by changing how the body absorbs nutrients, which can elevate fracture risk and may play a role in the development of metabolic bone disease, according to the researchers. After more than a decade of studying the relation- ship between metabolic bone disease and gastric bypass, Dr. Torquati believes a dearth of a key vitamin and mineral may explain why gastric bypass patients may be more susceptible to fracture. "In the early years of bariatric surger y expansion, we saw many patients develop- ing changes in the bone metabolism that potentially increase their risk of fractures," Dr. Torquati says. "At that time, this was sec- ondary to inadequate supplementation with vitamin D and calcium. In the last 10 years, all the patients undergoing bariatric surgery are receiving supplemental doses of vitamin D and calcium, and we very rarely see detrimental changes in the bone metabolism." REASSESSING OBESITY'S BENEFITS FOR BONES This study may prompt a reevaluation of obe- sity's role in protecting against osteoporosis. "The generally accepted notion that obesity is protective when considering the risks of fracture may not be as straightforward as previously thought," the researchers wrote. "The relationship between BMI, body compo- sition and bone density may play an important role when evaluating the risk of fracture in patients with obesity." Dr. Torquati says the study should provide peace of mind to patients who may be con- sidering bariatric surgery but worry about bone health. "Our results showed that bariatric surgery may be associated with lower odds of fracture in the general population of patients with obesity," he says. "Therefore, patients who are concerned about worsening osteoporosis after bariatric surgery should be reassured knowing this will not result in an increased risk of postoperative fractures, especially in patients undergoing sleeve gastrectomy." n More Research Needed Into High-Risk Patient Population A RUSH UNI V ER SIT Y Medical Center study found that reduced risk of bone fracture is a benefit of bariatric surgery, possibly as a result of improved mobility and reduced fall risk deriving from weight loss. "We were pleasantly surprised that the risk of bariatric surgery is reduced when we considered the entire age group of patients having surgery," says study author Alfonso Torquati, MD, MSCI, Helen Shedd Keith Professor and Chair of the Department of Surgery at Rush University Medical Center. "More studies are needed to evalu- ate the fracture risk in postmenopausal women who are already at higher risk of osteoporosis." SPECIAL CLINICAL SECTION: BARIATRICS M D N E W S . 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