Metabolic Impact of Bariatric Surgery on Rheumatic Diseases

Obesity is associated with a number of comorbid conditions, including rheumatic diseases. However, in some cases, excess weight loss can reverse the risk for disease progression and even improve these conditions.

While bariatric surgery is considered the sole option for long-term dramatic weight loss, it is primarily indicated for people with obesity and severe associated comorbidities.¹ To understand the long-term effects of bariatric surgery — not just on weight loss, but also on other chronic conditions — it is essential to view the physiological responses in context of changes to the gastrointestinal tract morphology.

Bariatric procedures have shown positive effects on comorbid diseases like diabetes and hypertension; therefore, it is not farfetched to suggest that surgically induced weight loss may have similar effects on rheumatic disease outcomes. However, through metabolic and musculoskeletal interactions, it is important to recognize potential consequences of bariatric surgery on rheumatic comorbidities, especially in bone health.

How does bariatric surgery promote weight loss?

Obesity is a metabolic condition, and dramatic weight loss changes the way bodies utilize energy and maintain homeostasis. Even though bariatric surgery is largely restrictive, several procedures rely on malabsorptive mechanisms to increase weight loss.² In other words, bariatric surgery cuts calories as well as alters the pathways that regulate the appetite and control the distribution and the rate of energy use.

Besides reducing the mechanical load of joints, bariatric surgery also affects changes to energy metabolism by mediating bone and fat crosstalk.¹ For example, certain neuropeptides that typically regulate bone formation in an environment of high calorie intake and weight gain, repress osteoblast activity based on signals of starvation (as occurs in dramatic weight loss).³ Also, due to the reduction of ingestion of nutrients and minerals, calcium from the bone is released into the blood, further changing the composition of bone tissue.⁴

This means that while bariatric procedures can be successful at weight loss, they can have a rather deleterious effect on bone tissue. Hence, it is important to explore the effects of bariatric surgery on diseases that are not only influenced by metabolic function, but also by those diseases that further modulate the musculoskeletal system.

How are obesity and rheumatic diseases related?

Rheumatic diseases are primarily characterized by inflammation of musculoskeletal tissues, including joints, tendons, ligaments, bones, and muscles. Obesity, while chiefly a metabolic condition, has also been associated with low-grade inflammation, specifically of white adipose tissue.¹

The impact of obesity on rheumatic diseases — besides imposing an abnormally large mechanical load on structural tissues — attenuates the inflammatory mechanism by triggering increased production of proinflammatory mediators.² Obesity can induce the initiation and progression of rheumatic diseases through altered hormonal and metabolic pathways, and secondarily, by promoting inflammation.

A few studies observed improvements in rheumatic arthritis outcomes (in terms of disease severity and activity) following bariatric surgery. In these studies, the proportion of participants reporting moderate to severe disease activity dropped from 57% to 6% a year after surgery. In subsequent follow-up visits, 74% of patients achieved remission compared with 26% at baseline.¹

This article originally appeared on Rheumatology Advisor