How much weight can you lose on retatrutide?

In Phase 3 trials, retatrutide 12 mg produced a mean weight loss of 28.3% over 80 weeks (TRIUMPH-1) and 28.7% over 68 weeks (TRIUMPH-4). The earlier Phase 2 trial showed 24.2% at 48 weeks. Results are dose-dependent, and individual outcomes vary.

What were the weight loss results by dose in retatrutide trials?

In the pivotal Phase 3 TRIUMPH-1 trial (80 weeks, efficacy estimand): 4 mg produced about 19.0% weight loss, 9 mg about 25.9%, and 12 mg about 28.3%, versus 2.2% for placebo. The earlier Phase 2 trial (48 weeks) showed roughly 8.7% at 1 mg, 17.1% to 22.8% at intermediate doses, and 24.2% at 12 mg.

Is retatrutide the most effective weight loss drug?

Based on Phase 3 data, retatrutide's mean weight loss (up to 28.3% in TRIUMPH-1 and 28.7% in TRIUMPH-4 at 12 mg) is the highest reported for any anti-obesity medication in a pivotal trial, exceeding tirzepatide (about 22.5% in SURMOUNT-1) and semaglutide 2.4 mg (about 14.9% in STEP 1). However, no head-to-head trials have directly compared these drugs, and retatrutide is not yet approved.

Retatrutide Weight Loss Results — Phase 2 Clinical Trial Data

Phase 2 Trial Results: The Headline Numbers

The Phase 2 clinical trial of retatrutide, published in The New England Journal of Medicine in 2023, evaluated multiple dose levels in adults with obesity (BMI of 30 or greater) or overweight (BMI of 27 or greater) with at least one weight-related comorbidity.

Over 48 weeks of treatment, mean percentage body weight loss was:

Placebo: -2.1%
1 mg: -8.7%
4 mg (escalated from 2 mg): -17.1%
4 mg (escalated from 4 mg): -22.8%
8 mg: -22.8%
12 mg: -24.2%

The 24.2% mean weight loss at the 12 mg dose represents one of the largest reductions reported in any anti-obesity medication trial to date.

Responder Analysis

Beyond averages, responder analysis shows the proportion of participants who achieved specific weight loss thresholds:

At the 12 mg dose, over 90% of participants achieved at least 5% body weight reduction.
Approximately 75% to 80% achieved at least 10% weight loss.
More than 50% of participants on the 12 mg dose achieved at least 20% weight loss.
A notable subset of participants on higher doses achieved 25% or more total body weight reduction.

These responder rates indicate that the majority of participants, not just a few exceptional cases, experienced clinically meaningful weight loss.

Dose-Response Relationship

The data show a clear dose-response gradient: higher doses produced greater weight loss. The escalation strategy also mattered — participants who were escalated more gradually to 4 mg (starting from 2 mg) lost less weight than those escalated more directly, suggesting that achieving the target dose level is important for optimal results.

Notably, weight loss curves at 48 weeks had not yet fully plateaued at higher doses, suggesting that longer treatment durations could potentially yield even greater reductions. This is a key question that the longer Phase 3 trials are designed to answer.

Important Caveats

While these results are notable, several important factors must be considered:

Phase 2 data: This was a Phase 2 trial with approximately 340 participants. Phase 2 trials are smaller and often produce results that differ from larger Phase 3 confirmatory studies.
Controlled conditions: Participants in clinical trials receive regular monitoring, dietary counseling, and follow structured protocols. Real-world results may differ.
No head-to-head trials: Direct comparisons with other drugs like semaglutide or tirzepatide cannot be made from separate trials due to differences in study populations, design, and endpoints.
Not yet approved: Retatrutide is not approved or commercially available. The only access is through clinical trial participation.
Individual variation: Average results do not predict individual outcomes. Some participants lost substantially more or less than the mean.

What Phase 3 Trials Will Tell Us

The ongoing TRIUMPH Phase 3 program includes multiple trials with thousands of participants, longer treatment durations, and diverse populations. These trials will provide more definitive data on the magnitude and durability of weight loss with retatrutide, as well as longer-term safety information. Results are expected over the coming years.