What are the mechanisms of bariatric surgery and how do they affect bone health?

In general, there are 3 established procedures for dramatic weight loss: laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy, and laparoscopic Roux-en-Y gastric bypass. The first procedure is purely restrictive; however, the other 2 procedures combine restrictive and malabsorptive mechanisms of action.

Sleeve gastrectomy resects a significant part of the gastric fundus where ghrelin production is dramatically reduced, which, in turn, induces the action of appetite-regulating hormones.1 In Roux-en-Y gastric bypass, the digestive tract is rearranged, which causes changes in the production and secretion of neuroendocrine and gastrointestinal hormones (and leads to metabolic effects).

Both malabsorptive procedures are associated with a greater increase in bone turnover markers (in favor of increased bone resorption); also, losses in bone mineral density profoundly increase skeletal fragility. In fact, studies show that malabsorptive weight loss procedures were associated with increased risk for fracture, whereas there was no such association found with weight loss procedures such as gastric banding that were only restrictive in nature.1

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What are the consequences of bariatric surgery?

The primary consequence of bariatric surgery that poses a major risk to a rheumatic population is its deleterious effects on bone. As discussed, malabsorptive procedures cause hormonal adaptations and changes in body composition that result in a more fragile musculoskeletal system.

Another consequence of bariatric surgery that affects the musculoskeletal system is acute gout flare, which may be triggered by large changes in serum uric acid levels. In addition, early studies on bariatric procedures have associated various arthritic syndromes and rare joint and skin conditions with circulating immune complexes along with bacterial overgrowth and other byproducts from the resected bowel.1

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How is weight loss indicated in disease management?

Body mass index is a theoretically modifiable risk factor. While obesity is associated with worse rheumatic disease outcomes, excess weight loss has been indicated to improve the ability of an individual to respond to treatment. This was demonstrated in a study linking obesity in early rheumatoid arthritis with decreased likelihood of achieving disease control: the response rate to anti-tumor necrosis factor was much lower among obese patients than those at a normal weight.1

Weight loss has often been indicated for the management of a number of conditions. For example, losing weight can reduce uricemia levels and the incidence of gouty arthritis. In a study of patients with lupus and obesity, 42% of patients were able to decrease the number of immunosuppressive drugs they were taking and 19.3% were able to stop glucocorticoid therapy.1

Can bariatric surgery improve rheumatic diseases?

Labeling bariatric surgery as a “metabolic procedure” is thoroughly appropriate as these interventions can result in the improvement of metabolic parameters, including those of rheumatic conditions, eg, modifying hyperuricemia. However, if bariatric surgery is recommended, healthcare professionals should weigh its negative impact on bone health — and on a deeper level, the complications that occur when metabolic changes intersect with musculoskeletal function.

For individuals with morbid obesity and chronic comorbid conditions, excess weight loss can benefit overall health. But for rheumatoid conditions, awareness of the impact of bariatric surgery on musculoskeletal integrity is a crucial consideration. Understanding the appropriateness of the procedure (less malabsorptive and more restrictive) and aggressive supplementation with calcium and vitamin D may be valuable for improving clinical outcomes.4

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  1. Lespessailles E, Hammoud E, Toumi H, Ibrahim-Nasser N. Consequences of bariatric surgery on outcomes in rheumatic diseases. Arthritis Res Ther. 2019;21:83.
  2. Nikiphorou E, Fragoulis GE. Inflammation, obesity, and rheumatic disease: common mechanistic links. A narrative review. Ther Adv Musculoskelet Dis. 2018;10(8):157-167.
  3. Shi YC, Baldock PA. Central and peripheral mechanisms of the NPY system in the regulation of bone and adipose tissue. Bone. 2012;50(2):430-436.
  4. Dimitriadis GK, Randeva MS, Miras AD. Potential hormone mechanisms of bariatric surgery. Curr Obes Rep. 2017;6(3):253-265.

This article originally appeared on Rheumatology Advisor