What it means
Glucagon is secreted by the pancreas when glucose is low; it tells the liver to release glucose and burn fat, and it raises energy expenditure. On its own it would raise blood sugar. Paired with GLP-1 and GIP, which drive insulin and suppress appetite, the glucose rise is cancelled while the fat-burning and thermogenic effects remain.
Retatrutide is the first triple agonist (GLP-1 + GIP + glucagon) to reach late-stage trials; survodutide and mazdutide are dual GLP-1/glucagon agonists on the same principle.
Why it matters for longevity
Incretin drugs lose weight mainly by cutting intake, which also lowers metabolic rate and takes lean mass. Adding glucagon signalling raises expenditure and preferentially clears liver fat, which could mean more fat loss per kilogram, better outcomes for fatty liver, and perhaps less metabolic slowdown. Those are hypotheses the phase 3 trials are testing.
What the evidence says
The retatrutide phase 2 trial (Jastreboff 2023, NEJM, 338 adults with obesity) reported 24.2% weight loss at 48 weeks on the highest dose, with weight still falling at the end — the largest effect yet recorded for a drug. A sub-study found liver fat reduced by over 80% in most participants with fatty liver.
Side effects were gastrointestinal, as for the incretins, with a higher rate of heart-rate increase and some reports of skin sensitivity. Phase 3 (TRIUMPH) results are expected from 2025–2026; no cardiovascular outcome or long-term safety data exist yet, and nothing is known about lean-mass preservation versus the dual agonists.
How to measure or use it
- Not a biomarker; nothing to measure in blood beyond the usual metabolic panel.
- If the class is ever part of a plan, the questions are the same as for GLP-1: muscle protection, a DEXA baseline, HOMA-IR and liver enzymes tracked.
- Retatrutide remains investigational; it is not licensed anywhere as of 2025.
Related
- Retatrutide (research page) — what the triple agonist is studied for
- Tirzepatide (research page) — the dual agonist comparison
- Metabolic health — the markers the class moves
Frequently asked questions
Why add glucagon to a weight-loss drug?
For energy expenditure and liver fat oxidation, which the incretins do not provide. The incretin components cancel the glucose-raising effect.
How much weight did retatrutide trials show?
24% at 48 weeks in phase 2 at the highest dose, with the curve still falling.
Is retatrutide available?
No. It is in phase 3 trials, with results expected from 2025–2026.
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