Research
Hormonal
GLP-1 receptor agonists (semaglutide, tirzepatide, retatrutide) cause significant loss of lean muscle mass (up to 40% of total weight loss), which contributes to reduced resting energy expenditure and increased risk of sarcopenia and weight regain.
If you are taking GLP-1 drugs, expect to lose some muscle along with fat. To protect your metabolism and strength, you must prioritize resistance training and adequate protein intake during your weight loss journey.
GoodSupportsHIGH confidence
While much of the weight loss comes from fat mass, these treatments also result in the loss of lean mass, including muscle. This loss of muscle may contribute to difficulties in maintaining weight over the long term and can lead to sarcopenia.
Why this rating
Based on multiple cited clinical trials (STEP-1, SURMOUNT-1, Retatrutide Phase 2) and meta-analyses.
Source
Saving muscle while losing weight: A vital strategy for sustainable results while on glucagon-like peptide-1 related drugs
Maja Cigrovski Berković et al. · World Journal of Diabetes · 2025
DOI 10.4239/wjd.v16.i9.109123
narrative_reviewCited 2×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Combining GLP-1 receptor agonists with resistance training and/or specific nutritional strategies (e.g., higher protein, ketogenic therapy) preserves fat-free mass and muscle strength better than pharmacotherapy alone.Good
- Myostatin and activin A inhibitors (e.g., bimagrumab, trevogrumab, garetosmab) combined with GLP-1 agonists can increase lean mass and reduce fat mass more effectively than GLP-1 agonists alone.Moderate
Related findings · Hormonal
- Initial treatment for type 2 diabetes should be a combination of metformin and either an SGLT-2 inhibitor or a GLP-1 receptor agonist to achieve cardiorenal protection, rather than monotherapy or older agents like sulfonylureas.Strong
- For patients with specific monogenic obesity syndromes (leptin deficiency, POMC/PCSK1/LEPR mutations), targeted pharmacotherapy (recombinant leptin or setmelanotide) is highly effective and should be prioritized, unlike in polygenic obesity.Strong
- Continued weekly administration of 2.4 mg subcutaneous semaglutide prevents weight regain and promotes further weight loss in adults with overweight or obesity, whereas switching to placebo results in significant weight regain.Strong
This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →