Retatrutide Before and After: Results, Timeline & Efficacy Data

Phase 3 TRIUMPH-1 Results: 28.3% Weight Loss at 80 Weeks

Eli Lilly announced topline TRIUMPH-1 (NCT05929066) results on May 21, 2026. The randomized, double-blind, placebo-controlled trial enrolled 2,339 adults with obesity or overweight plus at least one weight-related comorbidity, excluding people with diabetes. At 80 weeks, mean weight loss was 19.0% on 4mg, 25.9% on 9mg, and 28.3% on 12mg. A prespecified extension followed 532 participants with baseline BMI of 35 or higher to 104 weeks at their maximum tolerated dose; those originally randomized to 12mg reached 30.3% mean loss.

For context, 28.3% weight loss on a 250-pound person is roughly 70 lbs. This is the current, larger, and longer-duration result. It supersedes the earlier Phase 2b figure below, which is retained here as historical context because it is still widely cited and because it is the source for most of the granular secondary-endpoint data (waist circumference, blood pressure, lipids) available for retatrutide so far.

For Comparison: The Earlier Phase 2b Trial (Superseded)

For three years the number attached to retatrutide was 24.2%, from the 48-week Phase 2b trial published in the New England Journal of Medicine in 2023 (n included dose-ranging arms from 1mg to 12mg, placebo-controlled, no active comparator). At 48 weeks, least-squares mean weight change was -8.7% on 1mg, -17.1% on 4mg, -22.8% on 8mg, and -24.2% on 12mg, versus -2.1% on placebo. That trial is where the site-wide secondary-endpoint data below comes from; TRIUMPH-1's full secondary-endpoint breakdown had not been published as of this writing.

Key Phase 2b Secondary Endpoints (12mg Dose, NEJM 2023)

Month-by-Month Timeline: What to Expect

Weight loss on retatrutide follows a predictable pattern tied to titration phase: slower in the first month while the body adapts, then accelerating as the dose rises toward 12mg. The breakdown below reflects typical titration experience and general GLP-1-class patterns, not a specific trial-reported monthly figure — trials measure at fixed checkpoints (80 and 104 weeks for TRIUMPH-1), not month by month.

Month 1: Starting Dose

Typical weight loss: 1-3 lbs

• Appetite changes: Noticeable reduction in hunger by week 2; cravings diminish
• Physical changes: Minimal visible change; mostly internal metabolic adaptation
• Energy: May dip slightly in week 1; usually stabilizes by weeks 2-4
• Side effects: Mild nausea is common in the first 1-2 days after each injection during early titration

Months 2-3: Escalation Phase

Typical weight loss: 3-8 lbs per month, accelerating

• Appetite changes: Suppression becomes the dominant experience for most users as the dose escalates
• Physical changes: First noticeable changes in waist and upper body by week 8-12
• Nausea: Tends to recur briefly at each dose step, then settle within a week or two

Month 4 Onward: 12mg Dose

Typical weight loss: 4-10 lbs per month, gradually slowing over time

• Physical transformation: Cumulative change becomes evident to people around you
• Side effects: Generally diminish once GI adaptation to the maintenance dose is complete
• Trial checkpoint: TRIUMPH-1 measured 28.3% mean loss at 80 weeks (roughly month 18-19) on 12mg — weight loss on this class continues well past the one-year mark for most people, which is a large part of why the Phase 3 number is higher than the older 48-week Phase 2b figure

Body Composition Changes Beyond Total Weight Loss

Retatrutide does not just reduce weight; it changes body composition. The glucagon-receptor component is thought to preferentially mobilize visceral fat — the metabolically active fat surrounding organs — which is consistent with the waist-circumference reductions reported in the Phase 2b trial exceeding what total weight loss alone would predict for some participants.

Subcutaneous Fat and Visible Changes

Users commonly report facial slimming, reduced neck and jaw fullness, and upper-arm changes as subcutaneous fat decreases, alongside abdominal fat loss. As with any large, relatively fast weight loss, some loose skin is common and varies by age, starting weight, and rate of loss.

Retatrutide vs Tirzepatide and Semaglutide

Retatrutide's Phase 3 result (28.3% at 80 weeks, 12mg) is higher than tirzepatide's Phase 3 SURMOUNT-1 result (20.9% at 72 weeks, 15mg) and semaglutide's STEP program result (approximately 15% at 68 weeks, 2.4mg). None of these are head-to-head trials — each drug was tested in its own placebo-controlled study with a different population, duration, and titration schedule, so read the gaps as estimates, not measured differences. Full breakdowns: retatrutide vs tirzepatide and retatrutide vs semaglutide.

Post-Treatment Weight Regain

Retatrutide is still investigational, and neither the Phase 2b nor the Phase 3 TRIUMPH-1 trial has published a dedicated post-discontinuation follow-up dataset as of this writing. Based on general experience with GLP-1/GIP/glucagon-class drugs, stopping treatment without a maintenance plan is commonly followed by appetite return and gradual weight regain over months, which is why most clinicians treat this class as a long-term therapy rather than a fixed course. Specific regain percentages quoted for retatrutide are extrapolated from the broader drug class, not retatrutide-specific data.

For more, see our guides on retatrutide efficacy and results, retatrutide dosing basics, and comparisons with Zepbound (tirzepatide) results and Wegovy (semaglutide) results.

Informational only, not medical advice. Retatrutide is an investigational drug not approved by the FDA or any other regulator as of August 2026. TRIUMPH-1 figures are from Eli Lilly's topline announcement of May 21, 2026; full peer-reviewed results had not published as of this writing. Talk to a licensed clinician about treatment decisions.