Muscle & Bone Loss Risks After Bariatric Surgery: What You Need to Know

Bariatric surgery refers to a group of procedures designed to help individuals with severe obesity lose weight by altering the digestive system. Common types include gastric bypass, sleeve gastrectomy, and adjustable gastric banding. These surgeries limit food intake to promote weight loss.

Although bariatric surgery effectively improves obesity-related health conditions like type 2 diabetes, high blood pressure, and sleep apnea, it can also lead to muscle and bone loss, making ongoing health monitoring and nutritional support essential after surgery.

Muscle Loss

A 2021 systematic review found that, on average, patients experienced a lean mass loss of >8 kg within the first year after weight loss surgery. This reduction in lean mass occurred predominantly within the initial three months, during which approximately one-third of the total weight lost was attributed to lean mass, underscoring that the majority of fat-free mass reduction happens shortly after surgery.

Subsequently, another study highlighted an increase in sarcopenia (a degenerative loss of muscle strength, muscle quantity and quality, and low physical performance that occurs with aging or immobility) within patients from 8% to 32% within 1‐year postbariatric surgery.

This significant loss in muscle poses serious risks such as an increase in falls and fractures, decreased mobility, increased risk of metabolic disorders such as type II diabetes and other chronic diseases, increased fatigue, and impaired immune function.

This is largely attributed to a significant reduction in calorie and protein intake which is compromised because of reduced gastric capacity.

For example, one study found a 66% reduction in protein intake in the first month post-surgery, which remained significantly below baseline even one year later.

Another important factor to consider is that the reduction in gastric capacity complicates the ability to consume 20-40 grams of protein in one sitting, which is considered optimal for stimulating muscle protein synthesis (MPS).

Bone Loss

A 2020 review showed a notable decrease in bone mineral density (BMD) post-surgery, with a 2%-5% drop observed at the lumbar spine within six months and a more severe 6%-10.5% reduction at the total hip within 9-12 months.

Additionally, a 2018 meta-analysis showed that there was a 29% increased risk of fractures among those who underwent biartric surgery compared to non-surgical counterparts.

The rate of falls leading to fractures is also shown to be five times higher in gastric bypass patients (8.3%) compared to those on intensive medical therapy (1.7%) over two years.

Bariatric surgery can significantly impact bone health for several reasons. For example, there is a dramatic reduction in calcium absorption from 32.7% to 6.9% post-surgery, a significant reduction in micronutrient intake, mechanical unloading secondary hyperparathyroidism, and shifts in gut and gonadal hormones.

Subsequently, nutritional deficiencies tend to persist for months to years, exacerbating the effects on BMD. It’s also important to note that adolescents, who are still developing peak bone mass, are particularly at risk.

These insights underscore the importance of regular monitoring of BMD and proactive management of micronutrients to mitigate bone health risks in bariatric surgery patients.

Why DEXA Scans Are Essential for Post-Bariatric Patients

Given the risks of both muscle and bone loss, DEXA scans offer a comprehensive way to monitor changes in body composition after bariatric surgery.

DEXA scans accurately measure muscle, fat, and bone – something standard scales and other measurement tools cannot do.

This data establishes a valuable baseline after surgery, which can help act as a reference to track changes over time and detect any rapid muscle or bone loss that may require intervention.