A new study found that for two years after bariatric surgery patients continue to experience bone loss.

Gastruc bypass is the most common form of weight loss surgery, but bone loss could persist following the procedure even after weight is stabilized, an Endocrine Society news release reported.

"The long-term consequences of this substantial bone loss are unclear, but it might put them at increased risk of fracture, or breaking a bone," said Elaine Yu, MD, MSc, the study's principal investigator and an endocrinologist at Massachusetts General Hospital, Boston. "Therefore, bone health may need to be monitored in patients undergoing bariatric surgery."

The most common method of measuring bone mineral density, called dual-energy x-ray absorptiometry (DXA), can also turn up with false results. The team decided to measure bone density loss using a a three-dimensional type of computed tomography (CT) dubbed quantitative CT. They looked at bone density in the lower spine and hip of 50 obese adult patients; 30 of the participants had bariatric surgery and 20 used a non-surgical weight loss method.

Two years later bone density was between five to seven percent lower in the spine and seven to 10 percent lower at the hip in the surgical group compared with those in the non-surgical group. Even after the patients stopped losing weight the bone density loss persisted.

"Therefore, the cause of the bone loss is probably not related to weight loss itself," Yu said. "The question is when is the bone loss going to stop? Over time this could be a problem in terms of fracture."

Obese adults tend to have above average bone densities, but they have higher rates of fracture in the lower legs than non-obese individuals. The study suggest people who have bariatric surgery and have risk factors for osteoporosis should get regular bone density tests.

 "This surgery is the most effective treatment for severe obesity and offers phenomenal health benefits," Yu said.