A new study concludes that for at least two years following weight loss surgery, patients will continue to lose bone even after their overall weight stabilizes. The results come from patients who have undergone gastric bypass surgery, the most common weight loss surgery type. The study was presented June 30, 2014, at the joint meeting of the International Society of Endocrinology and the Endocrine Society: ICE/ENDO 2014 in Chicago, Illinois.
According to the study’s principal investigator Elaine Yu, MD, MSc and endocrinologist at Massachusetts General Hospital, bone health should be monitored in patients who have weight loss. The team of researchers once found that patients who had gastric bypass surgery did, in fact, lose bone mineral density, an important factor in bone fragility, just one year following weight loss surgery. Because the rate of bone loss is so high, the researchers continued to monitor these factors in this study, which was funded by the National Institutes of Health.
Bone mineral density is typically measured with a standard imaging method called dual-energy x-ray absorptiometry or DXA. However, this method can often give inaccurate results in obese patients. This means that the researchers measured bone density differently with a method using a 3-D type of computed tomography or CT called a complete CT scan. They compared the bone density at the lower spine and the hip in 50 obese adults – 30 who had surgery and 20 who had lost weight in a non-surgical way. All of these non-surgery patients were similar to the baseline age, body mass index and sex. After surgery, the surgery patients all received high-dose vitamin D supplements as well as Calcium.
The study found that two years later, the bone ‘density was nearly 5-7% lower at the spine and over 7-10% lower at the hip in the surgical group studied then the nonsurgical control group in their research using both the DXA and the complete CT scans. Yu and her team also found that the surgical patients had persistent and substantial increases in bone resorption markers, which is the process of which bones break down. The bone loss in surgical patients occurred despite that they were not losing additional weight in the second year following surgery, and all had stable blood levels with adequate vitamin levels. This means that the bone loss is probably not related to weight loss on its own.
This study leads to the question of when is bone loss going to stop? The study’s researchers recommend that weight loss surgeries who have risk factors for osteoporosis receive bone density tests. It is common knowledge that obese adults do have higher bone densities then non-obese people. The study’s team plans to continue to investigate possible causes for bone loss. Yu and her team speculate that major changes in the fat and gastrointestinal hormones could affect bone density in these patients.