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...

By Dr. Frank Yap, MD | Medically reviewed by One Day MD Review Team | Originally published: August 24, 2026 | Last updated: September 29, 2026 Quick Answer: A healthy lifestyle may add years to life, and potentially a decade or more in some populations, but no scientifically valid number applies to everyone. The biggest gains come from not smoking, regular physical activity, a high-quality diet, a healthy body weight, and controlled cardiovascular and metabolic risk factors . One influential U.S. analysis projected about 14 more years for women and 12 for men at age 50 for people with five low-risk habits versus none, but that is an observational estimate, not a guarantee. Supplements and anti-aging drugs are not proven to add a specific number of years. Preventing falls and injury also protects healthspan: balance and strength training is the best-supported strategy. In this guide What the Best Evidence Shows Other Studies Point the Same Way How Much Does Each Lifestyle...