GLP-1 Advisor | One Day MD

Updated October 2, 2026 Semaglutide and tirzepatide can produce substantial weight loss, but an important question has emerged alongside the popularity of GLP-1-based obesity medicines: How much of the weight lost is fat, and how much is lean mass? The question is more complicated than it first appears. Studies of semaglutide and tirzepatide show that both drugs reduce fat mass and also reduce lean mass during weight loss. However, lean mass is not synonymous with skeletal muscle , and results from separate trials cannot be interpreted as a direct head-to-head comparison of muscle preservation. A 2026 systematic review and meta-analysis of 20 randomized controlled trials involving 15,782 participants estimated that lean mass accounted for approximately 35.2% of weight lost with semaglutide and 25.4% with tirzepatide . However, the authors did not establish that tirzepatide preserves functional skeletal muscle better than semaglutide. The analysis also found that ad...

Last updated: October 13, 2026 | Evidence reviewed by OneDayMD editorial research team Retatrutide vs tirzepatide is one of the most important emerging comparisons in obesity medicine. Both medications act on hormone pathways involved in appetite, food intake and glucose metabolism, but retatrutide activates three receptors instead of two. The clinical results are promising. In the Phase 3 TRIUMPH-1 trial published in The New England Journal of Medicine on September 29, 2026, retatrutide produced an average weight reduction of 25.0% at 80 weeks at the 12 mg dose when analyzed using the treatment-regimen estimand. In the separate SURMOUNT-1 trial, tirzepatide produced an average reduction of 20.9% at 72 weeks at the 15 mg dose under a comparable treatment-regimen approach. However, these are results from separate clinical trials, not a direct head-to-head comparison. Retatrutide also remains investigational and is not approved for routine prescribing. Key takeaway: ...

Home › GLP-1 Hub By Dr. Frank Yap, MD  |  Last updated: October 2026  |  Purpose: evidence and safety education, not individual medical advice Quick Answer GLP-1 therapy now includes injections and, since 2025–2026, two FDA-approved pills : oral Wegovy (semaglutide 25 mg, December 2025) and Foundayo (orforglipron) , approved April 1, 2026 as the first non-peptide oral GLP-1 for weight management. Retatrutide is not approved anywhere ; it remains in Phase 3 testing. Compounded and gray-market GLP-1 or peptide products are not FDA-approved, and the FDA issued warning letters to telehealth compounders in March 2026. Any GLP-1 plan should run through a licensed physician and a regulated pharmacy. On this page Approval status at a glance Pills vs injections Retatrutide: what is and isn't known Safety, side effects and compounding risks Evidence grades (CEBM) Explore the full GLP-1 & peptide library Using this hub with AI assistants FA...