Weight Loss Drugs Linked to Higher Muscle Loss, UNC Study Finds

Chapel Hill, United States, April 18, 2026 — A new study from the University of North Carolina School of Medicine has found that widely used weight loss and diabetes drugs are associated with higher-than-expected muscle loss during weight reduction, raising concerns about patient health and clinical monitoring.

The research, published in the Annals of Internal Medicine, examined incretin-based medications such as semaglutide and tirzepatide. These drugs are commonly prescribed to treat obesity and type 2 diabetes, but findings indicate that patients using them may be losing a disproportionate amount of muscle alongside fat.

Study finds elevated muscle loss during treatment

The study, led by Professor John A. Batsis, focused on evaluating body composition changes in patients undergoing weight loss with incretin-based therapies. Researchers found that while weight reduction occurred as expected, the proportion of muscle mass lost during the process was consistently higher than anticipated.

Muscle loss is a known component of weight reduction, but the extent observed in patients using these medications exceeded typical expectations. This suggests that current treatment approaches may not adequately account for changes in muscle mass during rapid or medically assisted weight loss.

The findings highlight a critical gap in understanding how these medications affect overall body composition, rather than simply total body weight.

Doctors urged to monitor muscle health

Based on the results, researchers are calling for increased clinical attention to muscle health in patients prescribed these drugs. The study recommends that healthcare providers regularly assess muscle mass and function in addition to tracking weight loss.

Monitoring muscle health is particularly important because loss of muscle can impact strength, mobility and metabolic health. Without proper oversight, patients may achieve weight loss goals while experiencing unintended declines in physical function.

The researchers also emphasized the need to include muscle-related measurements as standard endpoints in future clinical trials involving weight loss medications.

Limited data on older adults raises concern

A key limitation identified in the study is the lack of research involving older populations. According to the findings, very few clinical trials of these medications have included participants over the age of 60, and none have specifically focused on individuals aged 65 or older.

This gap is significant because older adults are more vulnerable to the effects of muscle loss, including increased risk of falls, reduced independence and lower quality of life. The absence of targeted data makes it difficult to assess how safe or effective these treatments are for aging populations.

The study underscores the need for dedicated research examining how incretin-based therapies affect muscle preservation in older patients.

Call for expanded research and revised evaluation methods

Researchers are urging the development of new clinical trials designed to better understand the relationship between these medications and muscle health. Future studies should incorporate detailed body composition analysis and focus on outcomes such as mobility, strength and overall wellbeing.

The findings also contribute to a broader discussion about how weight loss success is measured in clinical settings. Current approaches often rely heavily on total weight reduction, which does not distinguish between fat loss and muscle loss.

By highlighting the limitations of weight-based metrics, the study suggests that more comprehensive evaluation tools are needed to ensure that treatments support long-term health outcomes.

Implications for obesity and diabetes treatment

Incretin-based medications like semaglutide and tirzepatide have become increasingly popular due to their effectiveness in reducing body weight and improving blood sugar control. However, the new findings indicate that their impact on muscle mass must be carefully considered.

The study emphasizes that while these drugs remain valuable tools in managing obesity and type 2 diabetes, their use should be accompanied by strategies to preserve muscle mass. This may include nutritional interventions, resistance exercise or adjustments in treatment protocols.

As the use of these medications continues to expand, the research highlights the importance of balancing weight loss outcomes with overall physical health, ensuring that patients benefit without unintended negative effects on muscle and mobility.