New Insights: GLP-1s and Lean Muscle in Weight Loss
A common concern with weight loss, including that achieved with GLP-1 drugs, is the potential for muscle loss. However, new research suggests that GLP-1 and dual GLP-1/GIP receptor agonist treatments can effectively promote fat loss while minimizing the reduction in lean muscle mass.
This research, which will be presented at the European Congress on Obesity (ECO 2025), indicates that combining these medications with supervised care, strength training, and adequate protein intake is crucial for preserving muscle during weight loss. The study, conducted by obesity experts in New York, supports the growing evidence that these medications are effective tools for managing obesity.
Understanding GLP-1 Receptor Agonists
GLP-1 receptor agonists, such as semaglutide and liraglutide, were initially developed for type 2 diabetes but have proven effective for obesity and weight loss. GLP-1 is a gut hormone that regulates blood sugar. GLP-1 agonists mimic or enhance this hormone’s effects, working by:
- Stimulating insulin release from the pancreas in response to food.
- Reducing glucagon secretion, which lowers blood sugar.
- Slowing gastric emptying.
- Suppressing appetite and promoting feelings of fullness.
These actions, including direct effects on the brain’s hunger centers, contribute to weight loss. Tirzepatide, a newer medication, targets both GLP-1 and GIP receptors and is also used for type 2 diabetes and obesity.
The Importance of Monitoring Body Composition
As the use of these therapies expands, it’s essential to monitor body composition, particularly muscle mass. Obesity medicine specialists play a key role in developing treatment plans that help patients lose weight while preserving lean muscle.
Study Details and Results
A six-month prospective cohort study involving 200 adults (ages 18-65) with overweight or obesity (BMI ≥ 25 kg/m²) examined the effects of GLP-1 receptor agonists on body composition. Participants received either semaglutide (n=80) or tirzepatide (n=120), along with guidance from a board-certified obesity physician on medication use, resistance training, and protein intake.
Body composition was assessed at the beginning, at three months, and at six months using multi-frequency bioelectrical impedance analysis. Researchers focused on changes in fat and muscle mass, and also tracked medication adherence, physical activity, and dietary intake. All 200 participants (99 men and 101 women) completed the study.
The average age of participants was 47, with a mean baseline BMI of 31.4 kg/m². After six months, women experienced an average weight loss of 12% (from 71 kg to 62 kg), and men experienced an average weight loss of 13% (from 101 kg to 88 kg).
Importantly, women lost an average of 10.8 kg of fat mass with only a minimal loss of 0.63 kg of muscle. Men lost an average of 12 kg of fat mass, with a minimal muscle loss of 1 kg.
Participants reported high rates of medication adherence (95% at three months and 89% at six months). Interviews indicated that regular strength training and sufficient protein intake were associated with better muscle preservation. The study is ongoing, and further data is being collected.
Source: Medical News Today, April 14, 2025