Bariatric surgeries are powerful and effective therapeutic approaches to combat obesity and Type 2 Diabetes (T2D). However, the long-term effect of gastrointestinal surgical procedures on bone health needs to be investigated. A recent study was conducted on patients undergoing RNY gastric bypass surgery, a common weight loss surgery type.

The study shows bone remodeling post-surgery, as early as three months. But the patients who initially gain bone mass will lose bone mineral density following weight loss surgery even after their overall weight stabilizes.

Anatomical changes can put patients at risk for mineral insufficiencies and consequent osteoporosis.[1] The patients are more prone to falls and fractures after the bariatric operation. Routine exercise and bariatric-specific vitamins are effective tools to mitigate bone loss in high-risk patients undergoing weight loss surgery.

Bone Metabolism

Bone physiology in obese individuals is a complex subject. It is a widespread belief that obese adults have higher bone densities than non-obese people, partially due to mechanical loading. Despite this common knowledge, there is a strong association between obesity and osteoporosis.

Osteoporosis is a bone disease that is more common in postmenopausal women and older men, leading to an increased risk of fractures.

An increase in total body fat is directly related to decreased bone mineral density. Lack of physical activity, lower levels of vitamin D, and poor nutrition contribute to reduced BMD in obese patients.

Study: Skeletal Response to Bariatric Surgery

On June 30, 2014, the bone loss after bariatric surgery study was presented 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, an endocrinologist at Massachusetts General Hospital, bone health should be monitored in weight loss patients. A team of researchers once found that patients who had RYGB surgery did lose bone mineral density just one year following weight loss surgery. Because the rate of bone loss is so high, the researchers continued to monitor the factors in this study, funded by the National Institutes of Health.

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. These non-surgery patients were similar in baseline age, body mass index, and sex. After surgery, the bariatric patients all received high-dose vitamin D supplements as well as Calcium.

bone loss osteoporosis weight loss surgery - BMD

Bone Mineral Density Testing

Bone Mineral Density (BMD), an important factor in bone fragility, 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 the obese population. The researchers measure bone density differently using a 3-D Computed Tomography type called a quantitative CT.

Study Results

Their research study used both the DXA and the complete CT scans. The data collected show that two years into post-op, the bone density was nearly 5-7% lower at the spine and over 7-10% lower at the hip in the surgical group than in the nonsurgical group.  Yu and her team also found that surgical patients had persistent and substantial increases in bone resorption markers, which is the process by which bones break down.

Several factors are involved in post-surgical BMD decline, including nutritional deficiencies, rapid weight loss, skeletal unloading, abnormalities in calciotropic hormones, as well as fat and gastrointestinal hormones.

The metabolic bone disease in surgical patients occurred despite not losing additional weight in the second year following surgery, and all had stable blood levels with adequate vitamin concentrations. This means that bone fragility is probably not related to weight loss on its own.

Bariatric-induced osteoporosis is not limited to malabsorptive procedures like RNY gastric bypass only. Vertical Sleeve Gastrectomy (VSG) or gastric sleeve causes similar bone loss to gastric bypass. Reports show rapid demineralization and reduced bone formation in VSG patients.


This study leads to the question of when the bone loss will stop. The study recommends that weight loss surgery patients with high-risk factors for osteoporosis receive bone density tests. Taking vitamins (D and Calcium) and nutritional supplements after malabsorptive procedures, such as Roux-en-Y gastric bypass, is a must for continued overall health.

The study’s team plans to investigate the factors involved in skeletal regulation and its mechanism. Yu and her team speculate that significant changes in fat-derived adipokines and gut hormones regulating appetite could affect bone density in these patients.

UPDATED September 2022 by Ron Elli, Ph.D.