GLP-1 Agonists: The Hidden Risks of Muscle and Bone Loss

GLP-1 receptor agonists (GLP-1RAs) like semaglutide have advanced the management of obesity and diabetes care, offering clinically meaningful and sustained weight loss and significant cardiovascular protection. Beneath the news headlines, there’s a critical part of the story we can’t afford to miss: not all weight loss is necessary nor healthy, and the loss of muscle and bone mass can have lasting consequences for patient function, frailty, and long-term outcomes.

GLP-1RAs are powerful hormones offering clinically relevant and patient desired outcomes, and their impacts on body composition warrant our focus. Data presented at the 2025 Diabetes Canada Conference and recent meta-analyses highlight that weight reduction from these medications isn’t just adipose, it’s also lean tissue, including muscle and bone. For health professionals, this means a new level of vigilance is needed to protect individuals’ strength, mobility, and independence, particularly in older adults and those at risk for sarcopenia.

Lean mass loss associated with GLP-1 therapy is clinically significant, with approximately 25–30% of total weight loss attributable to reductions in lean tissue, including skeletal muscle and bone. These changes have meaningful functional consequences for individuals, as measurable declines in muscle strength have been observed, including reductions in grip strength of approximately 20–25%, which can impair activities of daily living and contribute to an individual’s functional decline.

In addition, bone health may be adversely affected, with evidence indicating reductions in bone mass and strength that increase fracture risk, particularly among vulnerable populations. Although some recovery of muscle and bone mass may occur following discontinuation of therapy, this restoration of loss is often incomplete and proceeds more slowly in older or frail individuals.