Quick Answer: Retatrutide is an investigational weight loss drug from Eli Lilly that targets three hormone receptors (GLP-1, GIP, and glucagon) — one more than Mounjaro and two more than Ozempic. Phase 3 trial results released in December 2025 showed participants lost an average of 28.7% of their body weight (about 71 pounds) over 68 weeks, the highest weight loss reported for any obesity medication to date. It's not yet FDA approved, but could be by 2027. If you're currently on a GLP-1 medication or preparing for one, the same high-protein, portion-controlled eating strategies apply.
What Is Retatrutide and Why Is Everyone Talking About It?
If you've been following the weight loss medication space — Ozempic, Wegovy, Mounjaro, Zepbound — you've probably noticed a new name popping up: retatrutide. And there's good reason for the buzz. In December 2025, Eli Lilly released Phase 3 clinical trial results showing that retatrutide produced an average weight loss of 28.7% of body weight at 68 weeks.1 That's roughly 71 pounds for the average participant in the study. To put that in perspective, it's nearly double the weight loss seen with semaglutide (Wegovy) in similar trials.2
Retatrutide is what's called a "triple agonist" — it targets three hormone receptors in your body rather than one or two. While Ozempic works on one receptor (GLP-1), and Mounjaro works on two (GLP-1 and GIP), retatrutide hits all three: GLP-1, GIP, and glucagon.3 That third receptor — glucagon — is what makes retatrutide different, and potentially more powerful, than anything currently available.
It's still not FDA approved, and you can't get a prescription for it yet. But with seven more Phase 3 trial results expected throughout 2026 and potential approval projected for 2027, it's the drug that weight loss researchers and patients alike are watching most closely.1
How Retatrutide Works: The Triple Agonist Explained
To understand why retatrutide is getting so much attention, it helps to understand what "triple agonist" actually means in practical terms. Your body uses hormones to regulate hunger, blood sugar, and metabolism. GLP-1 medications work by mimicking some of these hormones — but each generation of drugs has added another layer.
GLP-1 (glucagon-like peptide-1) slows digestion, reduces appetite, and tells your brain you're full. This is what Ozempic and Wegovy target. GIP (glucose-dependent insulinotropic polypeptide) works alongside GLP-1 to further reduce appetite and improve how your body handles blood sugar. Mounjaro and Zepbound target both GLP-1 and GIP. Glucagon is the new addition with retatrutide — and this is where things get interesting. Glucagon tells your liver to release stored energy and appears to increase your body's resting energy expenditure, meaning you burn more calories even at rest.3
Think of it this way: the first two receptors help you eat less, while the third helps you burn more. That combination is likely why retatrutide's trial results have outperformed every approved weight loss drug on the market. A systematic review comparing these medications found that retatrutide (12 mg) achieved 22% weight loss from baseline, compared to 18% for tirzepatide and 14% for semaglutide.2 And those were Phase 2 numbers — Phase 3 results came in even higher.
What the Latest Clinical Trial Data Shows
The TRIUMPH-4 trial, whose results Eli Lilly announced in December 2025, is the first completed Phase 3 study for retatrutide.1 It enrolled 445 adults with obesity or overweight who also had knee osteoarthritis. Here's what the data showed at 68 weeks:
Participants on the 12 mg dose lost an average of 28.7% of their body weight — about 71.2 pounds from a starting average of 248 pounds. Nearly 59% of participants on the highest dose achieved at least 25% weight loss, and a meaningful subset exceeded 30% or even 35%.1 Beyond weight loss, participants also experienced a 75.8% reduction in knee pain scores, and about 1 in 8 patients on retatrutide were completely free of knee pain by the end of the trial.1
The side effects were consistent with what you'd expect from GLP-1-class drugs: nausea, diarrhea, constipation, and decreased appetite were the most common. One new finding was a signal for dysesthesia — a mild altered skin sensation — that hadn't been seen in Phase 2 trials. It was generally mild and rarely caused people to stop treatment.4
Seven additional Phase 3 trials are evaluating retatrutide for obesity without osteoarthritis, type 2 diabetes, obstructive sleep apnea, chronic low back pain, liver disease, and cardiovascular outcomes. Those results are expected throughout 2026.1
What This Means for Your GLP-1 Nutrition Strategy
Here's where this matters for your day-to-day eating: whether you're currently taking a GLP-1 medication, considering one, or keeping an eye on retatrutide for the future, the nutritional principles are the same — and they're more important than ever with a drug this powerful.
Retatrutide dramatically suppresses appetite through its triple-receptor mechanism. That means when you do eat, every bite counts more. Research consistently shows that people on GLP-1 medications who don't prioritize protein lose significant amounts of muscle along with fat — studies suggest up to 40% of weight lost can be lean muscle mass.5 With retatrutide producing even greater weight loss, protecting muscle through nutrition becomes critical.
The core principles haven't changed from what works with current GLP-1 medications. Aim for 100-120 grams of protein daily, which means prioritizing lean proteins at every meal — chicken, fish, eggs, Greek yogurt, cottage cheese. Eat smaller, more frequent meals (four to six per day rather than two or three large ones) to minimize the GI side effects that come with slower gastric emptying. Stay well hydrated with at least 64 ounces of water daily, and avoid greasy, fried, or heavy foods that tend to sit poorly in your stomach.5
For a complete breakdown of what to eat, portion strategies, and side effect management on GLP-1 medications, our Ultimate Guide to the GLP-1 Diet covers everything. And if you're just starting a GLP-1 medication now, our First Week on GLP-1 guide walks you through day by day.
Retatrutide vs. Current Medications: How It Compares
The question most people ask is straightforward: how does retatrutide stack up against what's already available? The short answer is that it appears to produce meaningfully more weight loss, though it's worth noting that we're comparing Phase 3 data (for retatrutide) to real-world data (for approved drugs), and head-to-head trials haven't been conducted yet.
Semaglutide (Wegovy) typically produces about 14-15% body weight loss in clinical trials. Tirzepatide (Zepbound) raised the bar to about 18-21%. Retatrutide's Phase 3 data shows 28.7% — nearly double Wegovy and significantly more than Zepbound.12 Analysts have projected that the longer TRIUMPH-1 trial (80 weeks) could show weight loss exceeding 30%.4
All three medications share similar side effect profiles — primarily GI issues like nausea and constipation — and all require the same protein-first, smaller-meal nutritional approach. If you're already doing well on a GLP-1 medication with a solid nutrition plan, you're building the habits that would serve you on retatrutide too. And the simplest way to make sure you're hitting your protein targets without the daily planning headache is a GLP-1-friendly high-protein meal plan — whether you use our ready-made meals or build your own from the template.
When Will Retatrutide Be Available?
As of early 2026, retatrutide is not FDA approved and cannot be legally prescribed or purchased. Any website or pharmacy claiming to sell retatrutide outside of a clinical trial is not offering a legitimate product — full stop.
The timeline looks like this: seven Phase 3 trials are expected to report results throughout 2026. If those results are positive (and the TRIUMPH-4 data strongly suggests they will be), Eli Lilly would then file a New Drug Application with the FDA. Based on typical review timelines, analysts project a potential approval in late 2026 or 2027.6 Retatrutide is made by the same company that makes Mounjaro and Zepbound, so manufacturing and distribution infrastructure is already in place.
In the meantime, you don't have to wait to start building the nutrition foundation that makes any weight loss medication work better. Getting your protein intake dialed in, building a meal prep routine, and establishing portion-controlled eating habits will position you for success — whether you're on a current GLP-1 or planning for the next generation. Our guide to preventing muscle loss on GLP-1 medications is a great place to start.
Frequently Asked Questions
Is retatrutide FDA approved?
No. As of early 2026, retatrutide is still in Phase 3 clinical trials. Eli Lilly has seven Phase 3 trials expected to report results in 2026, with potential FDA approval projected for 2027. It cannot be legally prescribed or purchased from any pharmacy.
How much weight can you lose on retatrutide?
In the Phase 3 TRIUMPH-4 trial, participants on the 12 mg dose lost an average of 28.7% of their body weight — about 71 pounds — over 68 weeks. These results are the highest reported for any obesity medication in clinical trials to date.
How is retatrutide different from Ozempic or Mounjaro?
Retatrutide targets three hormone receptors (GLP-1, GIP, and glucagon), while Ozempic targets one (GLP-1) and Mounjaro targets two (GLP-1 and GIP). The added glucagon activity appears to boost metabolic rate and fat burning, which likely explains the greater weight loss seen in trials.
What should you eat while taking retatrutide?
While retatrutide isn't available yet, its mechanism is similar to current GLP-1 medications. Experts recommend prioritizing protein (100-120g daily), eating smaller and more frequent meals, choosing whole foods rich in fiber and lean protein, staying hydrated, and avoiding greasy or fried foods. Our GLP-1 Diet Guide covers comprehensive nutrition strategies.
What are the side effects of retatrutide?
The most common side effects in trials were gastrointestinal: nausea, diarrhea, constipation, vomiting, and decreased appetite. These are consistent with other GLP-1 medications and were generally mild. A new signal for dysesthesia (altered skin sensation) was noted but was mild and rarely led to discontinuation.
The Bottom Line
Retatrutide represents the next leap in weight loss pharmacotherapy. Its triple-agonist approach — targeting GLP-1, GIP, and glucagon receptors simultaneously — has produced the most impressive weight loss results we've seen from any medication: nearly 29% body weight loss in 68 weeks. When the remaining Phase 3 trials report later this year, the picture will become even clearer.
But medication alone isn't a complete strategy. The people who get the best results from GLP-1 medications — current ones and future ones like retatrutide — are those who pair them with a protein-first nutrition plan, regular strength training, and consistent meal habits. If you want to build that foundation now, our Ultimate GLP-1 Diet Guide has everything you need. And if meal planning feels like one too many things to manage, Clean Eatz Kitchen's high-protein meal plans deliver 35+ grams of protein per serving, perfectly portioned for GLP-1 users — no subscription required.
References:
1. Eli Lilly and Company. "Lilly's triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial." Press release. December 11, 2025.
2. Moiz A, et al. Efficacy of Tirzepatide, Retatrutide, and Semaglutide for Weight Loss in Obese Individuals Without Diabetes. TheNNT. Systematic review of 26 RCTs.
3. Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine. 2023;389:514-526.
4. BioSpace. "Lilly's Retatrutide Scores Triple Trial Triumph With 26% Weight Loss, But New Safety Signal Emerges." December 12, 2025.
5. UCHealth. "Many people using GLP-1 weight loss drugs may not be eating enough nutritious food." May 2025.
6. Honest Care. "Retatrutide FDA Approval Timeline & Status 2025-2027." November 2025.
