A data essay
The Frontier
On its top maintenance dose, retatrutide cut mean body weight by 28.3% — against 22.5% for tirzepatide and 14.9% for semaglutide. The ladder steps up with each drug.
The Frontier
In absolute terms that's about 70 lb lost at the top dose, versus 52 for tirzepatide and 34 for semaglutide — roughly double the first-generation drug.
Read the fine print
These figures come from three separate studies — STEP-1, SURMOUNT-1, TRIUMPH-1 — run years apart, in different populations, against different placebo arms.
Read the fine print
TRIUMPH-1's patients began heavier — BMI 40 and 113 kg, against ~38 and ~105 elsewhere — and ran longest, at 80 weeks. No head-to-head trial exists. Read the gap as indicative, not a race.
The Depth
Plot the share of patients hitting each loss threshold. The averages hide the tail: what matters is how many reach the deep end.
The Depth
Over a quarter of retatrutide patients lost ≥35% of body weight — a threshold the others barely register. (Its shallow thresholds aren't published yet; full data lands at ADA, June 2026.)
Dose economy
Within TRIUMPH-1, the three doses line up cleanly: 19.0% at 4 mg, 25.9% at 9 mg, 28.3% at 12 mg.
Dose economy
Retatrutide's smallest tested dose — 4 mg, 19% — clears semaglutide's maximum, 14.9%. The floor of the new drug sits above the ceiling of the old one.
The Cost
Discontinuation for adverse events at 4 mg ran 4.1% — below TRIUMPH-1's own placebo arm at 4.9%. Efficacy with tolerability to spare.
The Cost
Push to 9 and 12 mg and discontinuation rises to 6.9% and 11.3% — the highest of any dose tested across all three drugs. The dose that loses the most also sheds the most patients.
The Cost
Plot efficacy against dropout and the curve bends: from 9 to 12 mg you buy ~2 more points of weight loss for a near-doubling of discontinuation.
The Signal
Retatrutide carries a signal the older drugs don't: dysesthesia — tingling or burning skin sensations — rising from 0.9% on placebo to 12.5% at the top dose.
The Signal
Nausea and GI effects are shared across the family. Dysesthesia isn't — it's largely absent from the GLP-1 and GLP-1/GIP drugs. Something retatrutide adds is doing this.
The Mechanism
The drugs differ by reach. Semaglutide hits GLP-1. Tirzepatide adds GIP. Retatrutide adds a third — the glucagon receptor, GCGR.
The Mechanism
Glucagon-receptor agonism is the new pathway — it raises energy expenditure and fat oxidation, the likely source of the extra loss. It's also the leading suspect for the dysesthesia. The same receptor that takes the frontier may carry the cost.
The Horizon
At two years the top dose hadn't plateaued: −30.3% and about 85 lb at 104 weeks, still drifting downward. How deep it ultimately goes is an open question.
Retatrutide posts the deepest weight loss the class has produced — and pays for it at the top of the dose ladder, through a side effect the older drugs don't share. Both trace to the same third receptor. The evidence is real but early: investigational, drawn from separate trials, with the full TRIUMPH-1 dataset still to be presented at ADA in June 2026. The frontier moved. The map of its edge is still being drawn.