EVIDENCE MATRIX / FOUR FILES
Compare the endpoint, not the hype
Tesamorelin, MOTS-c, tirzepatide, and semaglutide answer different questions in different species. Here is the honest side-by-side.
The short version
The four compounds cannot be ranked on one simple “muscle” scale. Tesamorelin has human randomized evidence for visceral-fat reduction and an increase in lean body mass in people with HIV-associated lipodystrophy [1]. MOTS-c has the most direct strength and movement tests—grip, gait, and running—but those intervention results come from mice [11]. Tirzepatide and semaglutide have large human programs showing weight and metabolic outcomes [13][16][18][19][20], while direct muscle-function testing is not the headline evidence in this corpus.
The useful comparison therefore has two axes. One is evidence maturity: cells, animals, observational human research, or randomized human trials. The other is endpoint directness: total weight, body composition, biomarkers, or measured physical function. A compound can be strong on one axis and weak on the other. The matrix below preserves that tension instead of declaring a winner the studies never tested.
The comparison matrix
| File | Primary mechanism | Strongest evidence in this corpus | Body-composition signal | Direct muscle-function signal | Central gap |
|---|---|---|---|---|---|
| Tesamorelin | GHRH receptor; endogenous GH/IGF-1 axis | Human randomized trials in HIV lipodystrophy [1][3][5][6] | Visceral, trunk, hepatic fat; lean body mass [1] | Not established in cited trials | Functional meaning and broader-population generalizability |
| MOTS-c | Mitochondrial stress signaling; AMPK, NRF2, CK2 | Cell and animal intervention studies; human observational cohort [8][9][11][12] | Atrophy and metabolic pathways in animal models [8] | Grip, gait, treadmill performance in mice [11] | No human efficacy or safety trial |
| Tirzepatide | Dual GIP/GLP-1 receptor agonism | Large randomized human obesity and diabetes trials [13][16][17] | Weight loss; lean-tissue concern in broader program | Not a primary endpoint in cited core trials | Function during substantial weight reduction |
| Semaglutide | GLP-1 receptor agonism | Large randomized weight, cardiovascular, and kidney trials [18][19][20] | Weight loss; lean-tissue concern in broader program | Not a primary endpoint in cited core trials | Function, frailty, and tissue quality during loss |
First axis: what did the instrument measure?
A scale measures total body weight. Imaging can estimate fat compartments and lean mass. Laboratory tests measure glucose, lipids, hormones, or other biomarkers. Grip dynamometry, walking speed, gait analysis, chair-rise tests, and treadmill protocols measure aspects of function. These instruments answer related but non-identical questions.
Tesamorelin's evidence is unusually specific about fat location. Trials detected visceral and hepatic changes, and pooled data recorded lean body mass [1][3]. MOTS-c studies are unusually direct about function, but only in animal models [8][11]. The incretin trials are unusually large and clinically consequential, yet their signature claims are weight, glycemic, cardiovascular, and kidney outcomes [13][17][18][19][20].
A responsible synthesis does not demote one endpoint simply because another is missing. It names the measured benefit and the unmeasured question separately.
Second axis: who was studied?
Species and population determine how far a result can travel. Tesamorelin's randomized results come mainly from adults with HIV-associated fat redistribution, not a general population seeking weight loss [1][3][5][6]. MOTS-c intervention work comes from cells and mice; its human cohort examined circulating peptide as a risk marker in chronic hemodialysis [9]. Tirzepatide and semaglutide trials enrolled large but still defined human populations, including adults with obesity, type 2 diabetes, cardiovascular disease, or kidney disease [13][16][17][18][19][20].
The question is never merely “Was there a study?” It is “Does this study's population match the claim being made?” A mouse grip result cannot establish human strength. A result in HIV lipodystrophy cannot silently become a general bodybuilding claim. A cardiovascular outcome does not answer a muscle-quality question.
Evidence maturity is not endpoint directness
MOTS-c makes the distinction visible. Its animal experiments directly measure performance, yet its human evidence is immature [9][11]. Semaglutide makes the opposite point. Its human evidence includes large clinical-outcome trials, but those trials do not directly settle the strength question [18][19]. Tesamorelin sits between: randomized human body-composition evidence without matching function tests [1]. Tirzepatide adds powerful human weight-loss evidence and the same need to connect tissue change to physical capability [13][16].
This two-axis view blocks a common rhetorical trick. A marketer can borrow the directness of an animal endpoint and the prestige of an unrelated human trial, then speak as though both belong to one proven claim. They do not. Each citation on this site stays attached to its own compound, population, and outcome.
What would close the gap?
The next informative trial would measure body weight, fat mass, appendicular lean tissue, and muscle quality alongside grip strength, walking speed, chair-rise performance, endurance, and patient-important mobility. It would repeat those measures rather than relying on a single snapshot, and it would report whether baseline age, frailty, disease, or rate of weight change altered the result.
Until such evidence is available across compounds, no credible winner can be named for strength preservation. The best-supported conclusions are narrower. Tesamorelin changes fat distribution and lean mass in a particular HIV population [1]. MOTS-c changes functional outcomes in mice [11]. Tirzepatide and semaglutide produce clinically meaningful weight and metabolic outcomes in defined human trials [13][16][18][19][20]. Those statements are strong precisely because they stop where the data stop.