The Study
(470) Preservation of Lean Mass under GLP-1/GIP-Based Pharmacotherapy: Effects of Testosterone and Resistance Training – A Five-Arm, Randomized, Open-Label Parallel-Group Study in Obese Men
This study gave different treatments to groups of men trying to lose weight and saw which group kept more muscle. Because they randomly assigned who got what, we can guess that the treatments caused the differences in muscle loss — but only in men with low testosterone. It doesn't prove it works for everyone.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
When obese men with low testosterone take weight-loss drugs, they often lose muscle too. This study tested if adding testosterone, lifting weights, and eating more protein can stop that.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 564 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — losing 38% of weight as muscle is harmful; gaining muscle while losing fat is ideal for health and strength.
- 2Without extra help: 38% of weight lost was muscle.
- 3With testosterone only: 26% muscle loss.
- 4With testosterone + weights: 16% muscle loss.
- 5With all three (testosterone + weights + high protein): muscle GAINED by 4.2%.
- 6Sexual function improved with testosterone, worsened without it.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
The Journal of Sexual Medicine
Year
2026
Authors
F. Sommer, S. Nocht
Related Content
Claims (5)
In obese men with low testosterone taking GLP-1/GIP agonists to lose weight, adding testosterone therapy, three weekly resistance training sessions, and a high-protein diet prevents muscle loss and increases fat-free mass by 4.2% over 26 weeks, whereas GLP-1/GIP therapy alone causes 38% of the weight lost to come from muscle tissue.
In obese men with low testosterone who are taking GLP-1/GIP therapy, adding testosterone replacement changes the composition of weight loss so that a smaller percentage comes from muscle tissue and more comes from fat.
In obese men with low testosterone on GLP-1/GIP therapy, adding resistance training to testosterone replacement reduces the amount of muscle lost during weight loss from 26% to 16% compared to testosterone replacement alone.
In obese men with low testosterone on GLP-1/GIP therapy, consuming 2.2 grams of protein per kilogram of fat-free mass daily results in lean mass loss accounting for 32% of total weight loss.
In obese men with low testosterone who are taking GLP-1/GIP medication, adding testosterone replacement raises sexual function scores by 3.8 to 4.6 points, while not adding testosterone results in a drop of 2.1 points in those scores.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.