Retatrutide - A Game Changer in Obesity Pharmacotherapy

I have not had very good experiences with GLP-1 drugs. The appetite suppression was nice, but the gastrointestinal side effects were a deal breaker. Semaglutide and Tirzepatide both shut down my digestive system. My wife has been on Retatrutide for a few months with very good results. I need to lose some stubborn belly fat, so I decided to give it a try. After 2 weeks of use, I have lost 8 pounds and have zero side effects. Retatrutide is not yet FDA approved but has gone through clinical trials and has so far been deemed safe and effective. This drug is a GLP-1, GIP and Glucagon Receptor activator.

So far so good... we'll see how it goes.

Could a single weekly injection deliver unprecedented weight loss while preserving muscle mass and improving cardiovascular health? For men on testosterone replacement therapy (TRT) struggling with stubborn body fat despite optimized hormone levels, this question has taken on profound significance. Retatrutide, a groundbreaking triple hormone receptor agonist, is reshaping our understanding of metabolic pharmacotherapy and offering hope where previous GLP-1 medications have fallen short.

The December 2024 release of Phase 3 TRIUMPH-4 trial results marked a watershed moment in obesity medicine: participants on the highest dose achieved an average weight loss of 28.7% over 68 weeks—the most substantial efficacy demonstrated in any obesity trial to date. Beyond the numbers, retatrutide addresses a critical concern for TRT patients: the quality of weight loss. While traditional GLP-1 medications have shown impressive weight reduction, concerns about muscle loss have tempered enthusiasm among men focused on body composition optimization.

Body Composition Effects: Addressing the Muscle Loss Concern​

For men on TRT committed to maintaining or building muscle mass, the body composition impact of any weight loss intervention demands scrutiny. The concern about lean mass loss with GLP-1 medications has been substantial, with some studies suggesting 25-40% of total weight loss comes from lean tissue.

The Fat-to-Lean Loss Ratio​

A June 2025 body composition substudy of retatrutide in people with type 2 diabetes provided reassuring data. Using dual-energy X-ray absorptiometry (DEXA) scanning—the gold standard for body composition assessment—researchers found that retatrutide's lean mass loss proportion aligned with other weight loss interventions, including bariatric surgery. Approximately 62-75% of weight loss came from fat mass, with 25-38% from lean mass.

While some lean tissue loss remains inevitable during substantial caloric deficits, retatrutide demonstrated greater reduction of visceral adipose tissue compared to subcutaneous fat. The 12 mg dose achieved mean fat mass reduction of 26.1% over 36 weeks in the diabetic population, with preferential targeting of metabolically active fat depots.

Comparison of Body Composition Changes Across Weight Loss Interventions

Intervention	Total Weight Loss	Fat Mass Loss	Lean Mass Loss	Study Duration
Retatrutide 12mg	24.2-28.7%	~75%	~25%	48-68 weeks
Tirzepatide 15mg	20.2-21.3%	~75%	~25%	72 weeks
Semaglutide 2.4mg	14.9-17.4%	~60%	~40%	68 weeks
Bariatric Surgery	25-32%	~70%	~30%	12 months

For men on TRT, these findings suggest that retatrutide delivers substantial fat loss without disproportionate muscle sacrifice compared to other interventions. However, the absolute amount of lean tissue lost—potentially 15-20 pounds for someone losing 70 pounds total—underscores the critical importance of resistance training and adequate protein intake during treatment.

Retatrutide for Men on TRT: What the Triple Agonist Means for Fat Loss, Muscle Preservation, and Metabolic Health
Curated By Nelson Vergel | ExcelMale.com | Updated February 2026

Summary: Retatrutide is a first-in-class triple hormone receptor agonist (GIP/GLP-1/glucagon) from Eli Lilly that delivered an average 28.7% body weight loss in its Phase 3 TRIUMPH-4 trial—the highest recorded in any obesity medication trial to date. For men on testosterone replacement therapy (TRT), retatrutide offers a compelling combination of profound fat loss with preferential visceral fat reduction, a body composition profile comparable to bariatric surgery, and potential synergy with testosterone’s anabolic effects. This guide examines the clinical evidence, real-world experiences from the ExcelMale community, practical dosing protocols, side effect management, and key considerations for men integrating this medication with their TRT regimen. Retatrutide remains investigational and is not yet FDA-approved; seven additional Phase 3 trials are expected to report results in 2026.

Introduction: Beyond GLP-1 Medications​

What if the biggest barrier between you and the body composition you’ve been chasing isn’t your testosterone dose, your training program, or even your diet—but the pharmacological tools available to address metabolic dysfunction? For men on TRT who have optimized their hormone levels yet still battle stubborn visceral fat, insulin resistance, or the metabolic consequences of years spent overweight, the arrival of retatrutide represents more than just another weight loss drug. It represents a fundamentally different approach to metabolic therapy.
In 30 years of advocacy, I’ve heard from thousands of men who describe the same frustration: they’ve dialed in their testosterone, committed to the gym, and cleaned up their diet—yet the belly fat persists. Semaglutide and tirzepatide opened doors for many of these men, but gastrointestinal side effects forced a significant number to abandon treatment. Others achieved meaningful weight loss only to watch their lean mass decline alongside their fat. Retatrutide addresses both of these limitations through its unique triple-receptor mechanism, and the clinical data emerging from Eli Lilly’s TRIUMPH program is, frankly, the most impressive I’ve seen in decades of following metabolic medicine.
This article provides a comprehensive, evidence-based guide to retatrutide for men on TRT. We’ll examine the science behind its triple-agonist mechanism, break down the Phase 2 and Phase 3 clinical trial results, address the critical question of muscle preservation, review side effects including a novel safety signal, and offer practical guidance for those considering this medication. Throughout, we’ll integrate insights from the ExcelMale community—real men sharing real experiences that clinical trial data alone cannot capture.

How Retatrutide Works: The Triple Agonist Advantage​

To understand why retatrutide produces results that dwarf its predecessors, you need to understand what separates a triple agonist from the single- and dual-receptor medications already on the market. Semaglutide (Ozempic, Wegovy) activates only the GLP-1 receptor. Tirzepatide (Mounjaro, Zepbound) activates both GLP-1 and GIP receptors. Retatrutide activates all three—GLP-1, GIP, and glucagon receptors—creating a pharmacological trifecta that no other approved or investigational medication currently replicates.

GLP-1 Receptor Activation​

The GLP-1 component provides the foundation that most men on TRT are already familiar with from semaglutide and tirzepatide. GLP-1 receptor activation slows gastric emptying, producing sustained satiety after meals. It reduces appetite through direct effects on hypothalamic hunger centers. It enhances glucose-dependent insulin secretion, meaning it helps your body handle carbohydrates more efficiently without the dangerous hypoglycemia risk associated with insulin or sulfonylureas. For TRT patients, this translates to more stable blood sugar, reduced cravings, and a natural caloric deficit that doesn’t require white-knuckling through hunger.

GIP Receptor Activation​

Glucose-dependent insulinotropic polypeptide (GIP) activation works synergistically with GLP-1 to enhance insulin secretion and improve glucose metabolism. But GIP’s most relevant benefit for our population may be its apparent modulation of gastrointestinal tolerability. Multiple ExcelMale members who could not tolerate semaglutide or tirzepatide have reported markedly better GI tolerance on retatrutide. One member described his experience plainly: “I could not handle any semaglutide in the past, even 0.1 mg gave me hellish nausea and lethargy. But retatrutide is different—absolutely no nausea or lethargy, if anything a good energy boost.” Retatrutide shows the highest potency at the GIP receptor (EC50: 0.0643 nM), which may partly explain these tolerability advantages.

Glucagon Receptor Activation: The Game Changer​

The glucagon receptor component is what truly sets retatrutide apart. Glucagon’s metabolic effects are precisely what men on TRT struggling with stubborn body fat need most. Glucagon promotes hepatic fat oxidation—it literally tells your liver to burn fat. It increases energy expenditure through thermogenesis, particularly in brown adipose tissue. It enhances lipolysis in adipose tissue, mobilizing stored fat for fuel. And it preferentially targets visceral fat, the metabolically dangerous intra-abdominal adiposity that drives insulin resistance, cardiovascular risk, and excessive aromatase activity.
For men on TRT, that last point deserves emphasis. Visceral fat is rich in aromatase, the enzyme that converts testosterone to estradiol. Reducing visceral fat stores can meaningfully reduce estradiol conversion, potentially improving the testosterone-to-estradiol ratio without requiring aromatase inhibitor medications. This creates a virtuous metabolic cycle: less visceral fat means less aromatization, which means more bioavailable testosterone, which means better muscle preservation and further fat loss.

Clinical Trial Results: Record-Breaking Efficacy​

Phase 2 Results: Setting the Stage​

The Phase 2 data published in the New England Journal of Medicine in 2023 by Jastreboff and colleagues first revealed retatrutide’s extraordinary potential. In 338 adults with obesity, the 12 mg dose produced 24.2% average weight loss at 48 weeks. Remarkably, 100% of participants on the 12 mg dose achieved at least 5% weight loss, 93% achieved 10% or more, and 83% exceeded 15% loss. A parallel trial by Rosenstock et al. in patients with type 2 diabetes showed up to 16.94% weight loss at 36 weeks alongside HbA1c reductions of up to 2.02%—substantially outperforming both placebo and the active comparator dulaglutide.

Phase 3 TRIUMPH-4: Unprecedented Results​

The December 2025 release of Phase 3 TRIUMPH-4 topline results shattered expectations. In 445 adults with obesity or overweight and knee osteoarthritis, retatrutide demonstrated the following at 68 weeks:
• 12 mg dose: 28.7% average weight loss (32.3 kg / 71.2 lbs from a baseline of 248.5 lbs)
• 9 mg dose: 26.4% average weight loss (29.1 kg / 64.2 lbs)
• Placebo: 2.1% weight loss
• Nearly half of participants on the 12 mg dose lost at least 25% of their body weight; approximately one quarter exceeded 30%
To put these numbers in context, an average weight loss of 71 pounds approaches outcomes typically associated with bariatric surgery procedures like sleeve gastrectomy. The 28.7% weight reduction substantially exceeds tirzepatide’s 20.2% at 72 weeks and semaglutide’s 14.9% at 68 weeks. For a 250-pound man, this translates to roughly 72 pounds of weight loss versus 50 pounds on tirzepatide or 37 pounds on semaglutide—differences that are clinically and personally meaningful.

Cardiometabolic Benefits​

TRIUMPH-4 also demonstrated significant improvements in cardiovascular risk markers. Non-HDL cholesterol, high-sensitivity C-reactive protein (hs-CRP), and triglycerides all decreased meaningfully. Approximately 40% of participants were able to discontinue at least one antihypertensive medication. For men on TRT—a population that clinicians have historically monitored closely for cardiovascular risk—these metabolic improvements offer reassurance that retatrutide complements rather than complicates cardiovascular health management.

Body Composition: Fat Loss vs. Muscle Preservation on TRT​

Ask any man on TRT about his biggest concern with weight loss medications and the answer is almost universal: Will I lose muscle? This is not an idle worry. Studies of semaglutide have suggested that up to 40% of total weight loss may come from lean tissue—an alarming proportion for men who have spent years building or maintaining muscle mass.

What the Data Shows​

A June 2025 body composition substudy published in The Lancet Diabetes & Endocrinology by Coskun et al. used DEXA scanning to evaluate retatrutide’s effects on fat and lean mass in people with type 2 diabetes. The findings were reassuring: approximately 62–75% of weight loss came from fat mass, with only 25–38% from lean mass. The 12 mg dose achieved a mean fat mass reduction of 26.1% over 36 weeks, with preferential targeting of visceral adipose tissue over subcutaneous fat.
Body Composition Comparison Across Weight Loss Interventions

Intervention​	Total Weight Loss​	Fat Mass Loss​	Lean Mass Loss​	Duration​
Retatrutide 12 mg	24.2–28.7%	~75%	~25%	48–68 weeks
Tirzepatide 15 mg	20.2–21.3%	~75%	~25%	72 weeks
Semaglutide 2.4 mg	14.9–17.4%	~60%	~40%	68 weeks
Bariatric Surgery	25–32%	~70%	~30%	12 months

For men on TRT, these proportions are more favorable than semaglutide’s profile and comparable to tirzepatide and bariatric surgery. However, the absolute amount of lean tissue lost still demands attention. A man losing 70 pounds total would lose approximately 17–18 pounds of lean mass. This makes resistance training and protein optimization not just recommended but essential. The anabolic stimulus from testosterone therapy provides a meaningful advantage here—one that clinical trial participants, most of whom were not on TRT, did not have.

Practical Muscle Preservation Protocol for Men on TRT​

Based on the available evidence and community experience, men on TRT using retatrutide should prioritize the following strategies to minimize lean mass loss:
• Protein intake of 1.2–1.6 g/kg body weight daily, distributed across 3–4 meals, with at least 30–40 g per meal to maximize muscle protein synthesis
• Resistance training at least 2–3 times per week targeting all major muscle groups with progressive overload
• Prioritize protein-dense foods even when appetite is suppressed—several community members report difficulty eating meat on retatrutide, making protein shakes and high-protein dairy particularly valuable
• Monitor body composition with DEXA scans rather than relying solely on scale weight, which cannot distinguish fat loss from lean mass loss

Liver Health: Dramatic Reduction in Fatty Liver Disease​

One of retatrutide’s most impressive “secondary” benefits is its profound effect on metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD). A 2024 Nature Medicine study by Sanyal et al. evaluated 98 participants with at least 10% liver fat content. At 48 weeks, the 12 mg dose achieved an 86% mean reduction in hepatic fat, with 93% of participants normalizing their liver fat to below 5%. The 8 mg dose was nearly as effective, normalizing liver fat in 89% of participants.
For men on TRT, this finding has particular clinical relevance. Elevated liver enzymes are common in this population, and many men with metabolic syndrome carry undiagnosed fatty liver disease. Retatrutide’s direct glucagon receptor engagement in hepatocytes—liver cells express high concentrations of glucagon receptors—provides a mechanism of action that pure GLP-1 agonists cannot match. This positions retatrutide as potentially the most effective pharmacological intervention for MASLD available, surpassing even dedicated MASLD therapies currently in development.

Side Effects and Safety Considerations​

Gastrointestinal Effects​

Like all incretin-based therapies, retatrutide’s most common side effects involve the GI system. In TRIUMPH-4, nausea occurred in approximately 43% of participants at higher doses, vomiting in 21%, and diarrhea in 33%. These effects were generally mild to moderate and most prominent during the dose escalation phase. Gradual titration—starting at 2 mg and escalating every four weeks—substantially reduces GI severity compared to aggressive dose escalation.
Discontinuation rates due to adverse events were 12.2% for the 9 mg dose and 18.2% for the 12 mg dose, compared with 4% for placebo. Notably, Eli Lilly reported that discontinuation rates correlated strongly with baseline BMI and included participants who discontinued due to “perceived excessive weight loss”—a rather unusual reason for stopping an obesity medication. Among those with higher baseline BMI, discontinuation rates were lower.

Dysesthesia: A Novel Safety Signal​

TRIUMPH-4 identified an unexpected adverse event not seen in Phase 2 trials: dysesthesia, or abnormal tactile sensations, occurred in 8.8% of participants on the 9 mg dose and 20.9% on the 12 mg dose, compared with just 0.7% on placebo. This skin sensitivity manifested as tingling, numbness, or hypersensitivity to touch, typically described as mild and not associated with visible skin changes. No participants discontinued specifically due to dysesthesia, suggesting manageable severity despite the relatively high prevalence at the 12 mg dose.
The mechanism remains under investigation. Theories include glucagon receptor effects on peripheral nerve function, metabolic changes associated with rapid fat mobilization, or potential neurological effects related to the speed and magnitude of weight loss. Men considering retatrutide should be aware of this potential side effect and report any unusual sensory changes to their healthcare provider.

Libido and Sexual Function Considerations​

ExcelMale community members have reported a mild reduction in libido while on retatrutide, with one member attributing this to possible dopamine modulation in the gut. This is consistent with anecdotal reports from other GLP-1 medications, which are known to affect reward-driven behaviors—including reduced cravings for alcohol, nicotine, and food. The reduction appears to be dose-related and generally described as mild. Men on TRT may have a buffer against this effect due to the libido-supporting properties of optimized testosterone levels, but it remains a consideration worth monitoring.

Practical Dosing and Titration Guide​

Clinical trials established dose-escalation protocols designed to minimize GI side effects while building toward optimal efficacy. The standard TRIUMPH protocol initiates at 2 mg weekly, increasing by one dose step every four weeks:

Weeks​	9 mg Target​	12 mg Target​	Notes​
1–4	2 mg	2 mg	Assess tolerance
5–8	4 mg	4 mg	GI effects may peak
9–12	6 mg	6 mg	Adjust if needed
13–16	9 mg (target)	9 mg	Maintenance for 9 mg
17+	—	12 mg (target)	Full maintenance

ExcelMale community members report variable tolerance to escalation speed. Some individuals—particularly those with prior GLP-1 intolerance—benefit from even slower titration, extending early dose phases to 6–8 weeks before advancing. One member started at just 1 mg and gradually worked up to 4 mg over two months, achieving 20+ pounds of weight loss with virtually no side effects. Others have experimented with twice-weekly dosing at lower doses (e.g., 2×2 mg or 2×3 mg weekly) rather than a single weekly injection, reporting smoother appetite suppression and fewer GI issues.

Retatrutide and TRT: Potential Synergy for Body Recomposition​

The combination of testosterone replacement and a potent incretin-based therapy like retatrutide creates a physiological environment uniquely suited to body recomposition—the simultaneous loss of fat and preservation (or gain) of lean muscle mass.

How Testosterone Complements Retatrutide​

Testosterone’s anabolic properties directly counter the lean mass loss that accompanies any significant caloric deficit. While retatrutide creates a powerful fat-burning metabolic environment through appetite reduction, enhanced energy expenditure, and preferential visceral fat mobilization, testosterone ensures that the anabolic signals for muscle protein synthesis remain robust. This is particularly important given that retatrutide users typically experience profound reductions in food intake, which without anabolic support could accelerate muscle catabolism.
Emerging evidence suggests an additional layer of synergy. A 2025 Endocrine Society presentation found that GLP-1 medications may raise endogenous testosterone levels in obese men through visceral fat reduction—primarily by reducing aromatase-mediated conversion of testosterone to estradiol. For men already on TRT, the same mechanism would reduce excess estradiol production, potentially improving the testosterone-to-estradiol ratio and reducing the need for aromatase inhibitor co-therapy.

Monitoring Recommendations for Combined Therapy​

Men using retatrutide alongside TRT should work with their physician to monitor the following parameters:
• Comprehensive metabolic panel including liver function tests (ALT, AST), kidney function, and fasting glucose every 3–6 months
• Lipid panel to track cardiovascular improvements and guide statin therapy adjustments
• Estradiol levels, as significant visceral fat loss may reduce aromatization and alter E2 requirements
• Body composition assessment via DEXA scan at baseline and every 6 months
• Blood glucose including HbA1c, particularly if pre-diabetic or diabetic
• Heart rate, as mild increases (2–4 bpm) are expected and should be documented

Availability, Access, and FDA Timeline​

As of February 2026, retatrutide remains investigational and is not FDA-approved. Eli Lilly’s TRIUMPH Phase 3 program includes eight total trials; TRIUMPH-4 is the first to report topline results. Seven additional Phase 3 readouts are expected throughout 2026, evaluating retatrutide in general obesity populations (TRIUMPH-1), type 2 diabetes with obesity (TRIUMPH-2), cardiovascular outcomes (TRIUMPH-3), and additional indications including obstructive sleep apnea, chronic low back pain, and metabolic dysfunction-associated steatotic liver disease.
Based on typical FDA timelines, regulatory submission (NDA filing) is projected for late 2026, with potential FDA approval in late 2026 to mid-2027. Upon approval, pricing is expected to be comparable to or exceeding tirzepatide’s current list price of approximately $1,000 per month. Insurance coverage will depend on formulary decisions and remains uncertain.
Some ExcelMale community members report using retatrutide obtained from peptide suppliers and underground lab sources prior to FDA approval. This practice carries significant risks, including quality control variability, potential contamination, incorrect dosing, and legal ambiguity. The FDA has issued warnings about counterfeit versions of other weight loss peptides, and similar concerns will extend to retatrutide. Men considering early access should weigh these risks carefully and discuss them openly with their healthcare providers.

Real-World Insights from the ExcelMale Community​

The ExcelMale forum has become one of the most active discussion spaces for men sharing retatrutide experiences. Several consistent themes emerge from community discussions:

Superior GI Tolerability​

Multiple members who experienced severe nausea, constipation, or digestive shutdown on semaglutide or tirzepatide report markedly better GI tolerance with retatrutide. One member described losing 8 pounds in his first two weeks on just 1 mg weekly with zero GI side effects—after both semaglutide and tirzepatide had been deal-breakers for him. His wife’s experience was similarly positive, losing 50–60 pounds over 6–8 months on 3 mg twice weekly with minimal issues.

Dramatic Appetite and Craving Reduction​

The craving-reduction effects appear particularly pronounced with retatrutide. Forum members consistently report not just reduced appetite but a fundamental shift in food preferences and addictive behaviors. One member noted his wine consumption dropped by half—not through willpower, but through genuine loss of interest. Another described the appetite reduction as allowing him to eat normally but in much smaller quantities: typical lunch portions dropped from 400g to 150g of ground beef, while maintaining sustained energy. The reduction in alcohol cravings echoes a broader pattern seen across incretin-based medications, where GLP-1 receptor activation in brain reward centers appears to modulate addictive behaviors.

Individual Variability in Response​

Not all experiences are uniformly positive. One community member reported persistent insomnia at any dose of retatrutide, eventually discontinuing and restarting at a micro-dose (300 mcg twice weekly) to assess tolerability. Another reported concerns about libido reduction, describing it as “mild” but noticeable—“harder to finish” rather than absent desire. These individual variations underscore that even a medication with superior average tolerability will not suit every patient. The ExcelMale community’s collective wisdom suggests starting conservatively and titrating based on individual response.

Related ExcelMale Forum Discussions​

Explore these community discussions for additional insights:

• Retatrutide: The Next Generation Triple Agonist Transforming Weight Management — Comprehensive overview article with community discussion of dosing, side effects, and body composition effects.
• Retatrutide – A Game Changer in Obesity Pharmacotherapy — Community members share real-world dosing experiences, GI tolerability comparisons, and weight loss results.
• Retatrutide Experiences — One of the earliest ExcelMale retatrutide experience threads, including a member’s wife losing 50 lbs over 6 months.
• Stacking with Retatrutide — Discussion of combining retatrutide with other peptides including BPC-157, MOTS-c, and growth hormone secretagogues.
• On Retatrutide and Not Feeling Effects — Troubleshooting thread for members not experiencing expected appetite suppression at initial doses.
• Looking for Retatrutide Experiences — Broader community experience thread with sourcing information and practical tips.

Key References​

1. Jastreboff AM, Kaplan LM, Frías JP, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. https://www.nejm.org/doi/full/10.1056/NEJMoa2301972
2. Rosenstock J, Frias J, Jastreboff AM, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes. Lancet. 2023;402(10401):529-544. https://pubmed.ncbi.nlm.nih.gov/37356446/
3. Eli Lilly. Retatrutide delivered weight loss of up to 71.2 lbs in TRIUMPH-4 Phase 3 trial. December 11, 2025. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average
4. Coskun T, Wu Q, Schloot NC, et al. Effects of retatrutide on body composition in people with type 2 diabetes. Lancet Diabetes Endocrinol. 2025;13(8):674-684. https://www.thelancet.com/journals/landia/article/PIIS2213-8587(25)00092-0/abstract
5. Sanyal AJ, Kaplan LM, Frias JP, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease. Nat Med. 2024;30:2037-2048. https://www.nature.com/articles/s41591-024-03018-2
6. Katsi V, Koutsopoulos G, Fragoulis C, et al. Retatrutide—A Game Changer in Obesity Pharmacotherapy. Biomolecules. 2025;15(6):796. https://pmc.ncbi.nlm.nih.gov/articles/PMC12190491/
7. Giblin K, Kaplan LM, Somers VK, et al. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH clinical trials. Diabetes Obes Metab. 2026;28(1):83-93. https://pubmed.ncbi.nlm.nih.gov/41090431/
8. Xiao YJ, Wang YN, Yu LX, et al. Efficacy and safety of retatrutide: a systematic review and meta-analysis of randomized controlled trials. Proc (Bayl Univ Med Cent). 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12026077/
9. Garvey WT, et al. Triple Receptor Agonist Retatrutide: A Potential Breakthrough in Obesity Pharmacotherapy. Am J Lifestyle Med. 2025;19(1):12-20. https://journals.sagepub.com/doi/10.1177/15598276251344827
10. Look M, Dunn JP, Kushner RF, et al. Body composition changes during weight reduction with tirzepatide in SURMOUNT-1. Diabetes Obes Metab. 2025;27(6):2720-2729. https://pubmed.ncbi.nlm.nih.gov/38584533/

Medical Disclaimer​

This article is provided for informational and educational purposes only and does not constitute medical advice. Retatrutide is an investigational medication not yet approved by the FDA. The information presented reflects clinical trial data and real-world community experiences but should not be used as a basis for medical decision-making without consultation with qualified healthcare providers. Men considering weight loss medications should consult with physicians experienced in both obesity medicine and hormone replacement therapy. Individual responses to retatrutide vary substantially, and the medication may not be appropriate for all patients. Never start, stop, or change any medication without the guidance of your healthcare provider.

About ExcelMale​

ExcelMale.com is a comprehensive men’s health forum with over 24,000 members and a 20+ year archive of discussions on testosterone replacement therapy, hormone optimization, sexual health, and metabolic wellness. Founded by Nelson Vergel, author of Testosterone: A Man’s Guide and Beyond Testosterone (available on Amazon), the forum provides evidence-based information and peer support for men navigating hormone therapy and overall health optimization. Visit ExcelMale.com to connect with thousands of men sharing their experiences, access expert insights, and explore comprehensive resources on men’s health.

 

I have not had very good experiences with GLP-1 drugs. The appetite suppression was nice, but the gastrointestinal side effects were a deal breaker. Semaglutide and Tirzepatide both shut down my digestive system. My wife has been on Retatrutide for a few months with very good results. I need to lose some stubborn belly fat, so I decided to give it a try. After 2 weeks of use, I have lost 8 pounds and have zero side effects. Retatrutide is not yet FDA approved but has gone through clinical trials and has so far been deemed safe and effective. This drug is a GLP-1, GIP and Glucagon Receptor activator.

So far so good... we'll see how it goes.

Retatrutide—A Game Changer in Obesity Pharmacotherapy - PMC

Obesity and type 2 diabetes mellitus (T2DM) are global health crises with significant morbidity and mortality. Retatrutide, a novel triple receptor agonist targeting glucagon-like peptide-1 (GLP-1), Glucose-Dependent Insulinotropic Polypeptide ...

pmc.ncbi.nlm.nih.gov

Retatrutide—A Game Changer in Obesity Pharmacotherapy​

Vasiliki Katsi 1,*, Georgios Koutsopoulos 1, Christos Fragoulis 1, Kyriakos Dimitriadis 1, Konstantinos Tsioufis 1
Editors: Othmar Moser1, Harald Sourij1

• Author information
• Article notes
• Copyright and License information

PMCID: PMC12190491 PMID: 40563436

Abstract​

Obesity and type 2 diabetes mellitus (T2DM) are global health crises with significant morbidity and mortality. Retatrutide, a novel triple receptor agonist targeting glucagon-like peptide-1 (GLP-1), Glucose-Dependent Insulinotropic Polypeptide (GIP), and glucagon receptors, represents a groundbreaking advancement in obesity and T2DM pharmacotherapy. This review synthesizes findings from preclinical and clinical studies, highlighting retatrutide’s mechanisms, efficacy, and safety profile. Retatrutide’s unique molecular structure enables potent activation of GLP-1, GIP, and glucagon receptors, leading to significant weight reduction, improved glycemic control, and favorable metabolic outcomes. Animal studies demonstrate retatrutide’s ability to delay gastric emptying, reduce food intake, and promote weight loss, with superior efficacy compared to other incretin-based therapies. Phase I and II clinical trials corroborate these findings, showing dose-dependent weight loss, reductions in Glycated Hemoglobin (HbA1c) levels, and improvements in liver steatosis and diabetic kidney disease. Common adverse effects are primarily gastrointestinal and dose-related. Ongoing Phase III trials, such as the TRIUMPH studies, aim to further evaluate retatrutide’s long-term safety and efficacy in diverse patient populations. While retatrutide shows immense promise, considerations regarding cost and the quality of weight loss beyond BMI reduction warrant further investigation. Retatrutide heralds a new era in obesity and T2DM treatment, offering hope for improved patient outcomes.
Keywords: retatrutide, obesity, incretins, type 2 diabetes mellitus

1. Introduction​

Obesity has emerged as a pressing global health crisis, often referred to as a pandemic due to its widespread prevalence and significant impact on public health. It is estimated to be responsible for approximately 3.4 million deaths each year worldwide, underscoring its severity as a major contributor to mortality rates [1]. Clinically, it is characterized by an excess accumulation of adipose tissue within the body, and it is formally defined as a body mass index (BMI) of ≥30 kg/m2. It can affect patients both on a psychological and physical level, with overweight and obese people found to be at risk for diabetes, cardiovascular disease, cancer, and premature death [2]. This has a significant toll on life expectancy, which is shown to be reduced by 7 years at the age of 40 years [3]. Added to that, it is constantly growing in scale with an estimated projection of overweight and obese adults at 1.35 billion and 573 million, respectively, by the year 2030 [4].
Coming hand in hand with obesity, type 2 diabetes mellitus (T2DM) poses a considerable threat to individual health and a significant burden on the world’s financial health policy. Described as a disorder of glucose homeostasis and insulin sensitivity, it is primarily triggered by uncontrolled hyperglycemia, and it is responsible for a large number of microvascular (like diabetic retinopathy, diabetic nephropathy, and diabetic neuropathy) and macrovascular complications (like diabetic foot syndrome, cerebrovascular events, and myocardial infarction) [5]. The presence of T2DM also increases susceptibility to a variety of cancers (such as liver, biliary tract, pancreas, stomach, colorectal, kidney, bladder, breast, and endometrial) and infections (like respiratory, urinary tract, and skin and soft tissue infections) [6].
A tight interplay between these two is a common finding in many patients, and many metabolic pathways show their close pathophysiological connection. For example, the global prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH) among diabetic patients is estimated at 65.33% and 66.44%, respectively [7].
Unhealthy diets and sedentary lifestyles are pivotal predisposing factors contributing to the growing global burden of obesity, T2DM, and metabolic dysfunction-associated fatty liver disease (MAFLD). Diets rich in saturated fats, refined carbohydrates, and ultra-processed foods—hallmarks of the Western dietary pattern—have been consistently linked to excessive adiposity, insulin resistance, and chronic systemic inflammation [8]. These conditions are central to the pathogenesis of both T2DM and MAFLD, forming a critical component of the broader metabolic syndrome. Additionally, prolonged physical inactivity further compounds these risks by diminishing metabolic flexibility and impairing insulin sensitivity, independent of body weight [9]. The synergistic effect of poor dietary quality and lack of exercise creates a fertile ground for the development and progression of metabolic disorders.
Intervention through lifestyle modification remains the first-line therapeutic strategy. Notably, adherence to the Mediterranean diet—a dietary pattern rich in fruits, vegetables, whole grains, olive oil, and lean proteins—has demonstrated significant improvements in hepatic steatosis and insulin resistance among patients with MAFLD [10]. Furthermore, structured exercise regimens incorporating both aerobic and resistance training have been shown to reduce liver fat content and improve glycemic control [11]. However, despite the well-documented benefits of lifestyle changes, maintaining long-term adherence remains a challenge for many individuals, often requiring multidisciplinary support and long-term behaviour change strategies. When necessary, pharmacological interventions are essential to eliminate the gap for effective prevention and management of these interrelated conditions.
Numerous pharmacological treatments seek to disrupt these harmful connections, with a considerable number focusing on the incretin hormonal pathways and appetite regulation. Three of the most common incretin peptide hormones are Glucagon-Like Peptide (GLP-1), Glucose-Dependent Insulinotropic Polypeptide (GIP), and Glucagon. The emergence of GLP-1 receptor agonists, such as the first clinically approved agonist, exenatide, in 2005, paved the way for the thorough exploration of these molecules [12]. Shortly, other molecules such as liraglutide, dulaglutide, and semaglutide came forth, offering a once-weekly dosage. Beyond achieving more effective glucose control and offering worthy weight loss, these medications achieved a reduction in rates of major adverse cardiovascular effects, heart failure, kidney disease, and cardiovascular death [13,14,15]. These promising results led to the development of the first dual agonists, with tirzepatide, a GIP and GLP-1 receptor agonist, being the most prominent one. Tirzepatide achieved significant reductions in Glycated Hemoglobin A1c (HbA1c) levels and body weight compared to placebo. Additionally, tirzepatide was found to have a more pronounced effect compared with the GLP-1 agonist semaglutide in people with T2DM. The incidence of gastrointestinal (GI) adverse events was increased compared with placebo; however, neither tirzepatide nor semaglutide increased the risk of serious adverse events or severe hypoglycaemia [16].
A first-of-its-class triple receptor agonist, retatrutide, aims to deliver a revolution in obesity and T2DM pharmacotherapy. This groundbreaking medication is shown to enhance therapeutic outcomes by delivering more pronounced reductions in both body weight and HbA1c levels than current pharmacotherapies.

2. Materials and Methods​

A review of the literature was conducted to examine the potential impact of the emerging drug retatrutide on T2DM and obesity pharmacotherapy. The search was carried out on Medline using the keywords: retatrutide, T2DM, obesity, and novel pharmacotherapy, in combination with the boolean operators AND or OR. Only articles published in English from 2005 onwards were included, with the most recent search conducted in April 2025.

3. Targeted Molecules​

3.1. Glucagon-like Peptide (GLP-1)​

GLP-1 is an incretin hormone that is predominantly secreted from the intestinal tract, mainly as a response to meals. Small Intestine L-cells are responsible for their production from a proglucagon gene [17]. Production of this molecule is also shown to occur in pancreatic α-cells and the central nervous system in areas like the nucleus tractus solitarius and microglia [18]. It predominantly acts by activating a receptor that induces stimulation of insulin release, decreases glucagon secretion, reduces food intake, and delays gastric emptying (GE) by affecting gastric and intestinal motility [19]. GLP-1 receptors can be found in a variety of tissues such as the pancreas, gastric mucosa, kidney, lung, heart, skin, immune cells, and brain. They are 463 amino acid heptahelical G protein-coupled receptors that, when activated, stimulate cyclic adenosine monophosphate (cAMP) formation followed by activation of protein kinase A pathways [20].
Especially regarding the central nervous system, the expression of GLP-1 receptors in reward-related regions, such as the hypothalamus, amygdala, nucleus accumbens, paraventricular nucleus, ventral tegmental area, locus coeruleus, and brain stem [21] may suggest a possible association between reward learning and symptoms like anhedonia in diseases such as depression. However, the multifactorial and polygenic nature of this diagnosis requires further investigation before establishing a rigid conclusion [22]. GLP-1 activation is also shown to reduce inflammation by reducing macrophage activity [23]. Its effects on satiety and food intake are found in healthy individuals as well as in obese and diabetic patients [24].

3.2. Glucose-Dependent Insulinotropic Polypeptide (GIP)​

Also excreted from intestinal K cells, GIP is a protein mostly postprandially secreted [25]. It consists of 42 amino acids that take form after proteolysis of a 153-amino acid precursor. GIP receptors exist as two isoforms, consisting of 466 and 493 amino acids, respectively, that, when activated, display an increase in intracellular calcium and arachidonic acid. Their activation is also related to adenylyl cyclase activation. By acting on these receptors that are expressed in multiple tissues, including primarily pancreatic β-cells and secondarily adipose and nervous tissue, GIP stimulates glycogen secretion both in normoglycemic and hyperglycemic states. It also reduces appetite by having a negative impact on GE and by enabling insulin release from the pancreas, acting in tandem with GLP-1 [26]. However, it acts in contrast with GLP-1 as much as glucagon release is concerned by enhancing its release. Furthermore, growth factor-dependent pathways such as MAPK (extracellular signal-regulated kinases 1 and 2 [ERK 1/2]) and protein kinase B are found to be affected by GIP activation [20]. GIP effects regarding adipose tissue are also described as it is shown to stimulate adipogenesis, inhibit lipolysis, and stimulate de novo lipogenesis [27]. Additionally, GIP is shown to have a direct influence on bone, inducing osteoblast activity [28].

3.3. Glucagon​

Finally, glucagon, formed from a precursor pro-glucagon molecule of 180 amino acids, is a hormone that is mostly found in pancreatic α-cells [19]. Production in the small intestine is also described [28]. After its discovery in 1921, its contribution to the pathophysiology of type 2 diabetes mellitus opened a new age in antidiabetic medications and in the study of metabolic diseases. It consists of 29 amino acids [29] and its gene is located on chromosome 2 [30]. Glucagon receptors are mainly found in the liver hepatocytes and in the kidneys. Less expression is also described in other tissues such as the heart, pancreas, adipose tissue, and the GI tract. Glucagon receptors are G protein-coupled receptors that, when stimulated, lead to an increase in intracellular cAMP and calcium that, in advance, activate the protein kinase A pathway [31,32]. Its main drive of release is low glucose blood levels, and glucagon receptors are found in many tissues, with hepatocytes being the most common place. Glucagon allows gluconeogenesis and glycogenolysis in the liver while blocking glycogenesis. These effects lead to high blood glucose levels. Glucagon also reduces GI motility [33] and, by acting on adipose tissue, decreases lipogenesis and induces lipolysis, leading to increased production of non-esterified fatty acids and ketone bodies. Glucagon is also found to affect brown fat in animal models, inducing thermogenesis and energy expenditure. However, human experiments have not proven more than a modest effect on energy expenditure, not achieving clinical significance [28].

4. General Aspects of Retatrutide​

Molecular Structure—Pharmacology​

A promising new therapy that targets all the previously mentioned molecules is the triple receptor agonist retatrutide. Retatrutide is a synthetic peptide acting as an agonist of GLP-1, GIP, and glucagon receptors (Figure 1). Retatrutide’s engineering allows it to bind uniquely to these receptors [34].

Figure 1.​

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Retatrutide’s mechanisms of action.
Retatrutide develops in a single continuous helical structure that allows it to run through the receptor’s transmembrane domain with its N-terminal segment. The C-terminal segment takes part in interactions with the N-terminal α-helix of the extracellular domain, the extracellular tip of the transmembrane helix 1 of the GLP-1 receptor, and the extracellular loop 1 of the GIP receptor. This molecule is more potent at the human GIP receptor (EC50: 0.0643 nM) and less potent at the GLP-1 (EC50: 0.775 nM) and glucagon (EC50: 5.79 nM) receptors [35]. It has a dose-dependent action and causes a decrease in gastric emptying, while with a half-life of 6 days, it can mostly be used on a weekly basis. Retatrutide shows mostly hepatic metabolism but does not interact with cytochrome P450 enzymes [36].
Its effects lead to significant weight reduction and to a decrease in HbA1c levels [37]. The most commonly occurring adverse effects are nausea, diarrhea, vomiting, and constipation. However, these resulted in not-so-rare incidents of therapy discontinuation, and their intensity was clearly linked with higher dosages. Practical studies indicate that the discontinuation rates of GLP-1RAs can reach between 20% and 50% within the first year, and patients often use significantly lower dosages compared to those tested in clinical trials [38]. Less common adverse effects were a temporary increase in alanine aminotransferase (ALT) levels, increased heart rate, and skin hyperesthesia [39].

5. Insights from Animal Studies​

In recent years, retatrutide has amassed a respectable number of animal and clinical studies (Table 1).

Table 1.​

Concise summary of key retatrutide studies.

[th]
Type of Study

[/th][th]
Year

[/th][th]
Studies

[/th]
[td]
Animal Study (mice)

[/td][td]
2017

[/td][td]
Jall et al.

[/td]
[td]
Animal Study (mice)

[/td][td]
2023

[/td][td]
Urva et al.

[/td]
[td]
Animal Study (mice)

[/td][td]
2024

[/td][td]
Ma et al.

[/td]
[td]
Phase I Clinical Study

[/td][td]
2022

[/td][td]
Coskun et al.

[/td]
[td]
Phase I Clinical Study

[/td][td]
2022

[/td][td]
Urva et al.

[/td]
[td]
Phase II Clinical Study

[/td][td]
2023

[/td][td]
Jastreboff et al.

[/td]
[td]
Phase II Clinical Study

[/td][td]
2023

[/td][td]
Rosenstock et al.

[/td]
[td]
Phase II Clinical Study

[/td][td]
2024

[/td][td]
Sanyal et al.

[/td]​

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With delayed GE being an important effect of weight-lowering drugs acting on glucagon, Urva et al. attempted to investigate retatrutide’s effect, compared with other selective GLP-1 receptor antagonists on animal models [40]. C57/B16 male obese mice (Jackson) were singly housed and maintained on a standardized diet (TD95217; Teklad) with ad libitum water; 16 h before the assessment of acute GE, mice were fasted overnight and treated subcutaneously with either vehicle (10 mL/kg; 40 mM Tris pH 8), long-acting glucagon receptor agonist, semaglutide, retatrutide, or combined semaglutide and long-acting glucagon receptor agonist. Mice were administered 0.5 mL of semi-liquid by oral gavage, and GE was subsequently assessed. GE delay, body weight, and food intake were also assessed following chronic (daily for 10 days) treatment with vehicle, semaglutide, long-acting glucagon receptor agonist, retatrutide, or combined semaglutide and long-acting glucagon receptor agonist. Retatrutide achieved delayed GE in mice in a dose-dependent fashion, as well as semaglutide. The dual combination of them did not manage to differ statistically from the usage of retatrutide alone. 10 nmol/kg of retatrutide achieved a bigger weight drop over 10 days than the other combinations. Furthermore, retatrutide showed the largest decreases in food intake, and chronic treatment for 10 days attenuated the described effects. However, there are some limitations to the study. The method used in the study is not the gold standard scintigraphy that involves radioactive tracers, and the researchers did not take into account secretion-based error [40].
Another study by Ma et al. aimed to compare the effects of retatrutide, liraglutide, and tirzepatide on diabetic kidney disease in db/db mice [41]. The seven-week-old male C57BL/KSJ diabetic db/db and db/m mice were housed in an ambient temperature of 21 ± 2 °C and humidity of 45 ± 10%, maintained under a 12 h light/dark cycle. At 8 weeks of age, the mice were randomly divided into 5 groups (each n = 6): db/m, db/db, db/db + Lira, db/db + Tirz, and db/db + Reta. Each treatment group was divided into two cages with three mice in each cage. The mice in db/db + Lira, db/db + Tirz, and db/db + Reta groups received daily subcutaneous injections of 10 nmol/kg of liraglutide, tirzepatide, and retatrutide for 10 weeks, respectively. The db/m and db/db groups were given an equal amount of saline intraperitoneally over the same time. The dose of the drug was adjusted weekly throughout the study period based on changes in the weight of the mice. Weekly, a glucometer was used to assess the fasting blood glucose (FBG) levels. HbA1c values were measured at the beginning and end of the experiment. After a duration of 10 weeks, urine samples were collected from individually housed mice in metabolic cages over a 24 h period, followed by recording of urine volumes and storage at −80 °C for further analysis. Subsequently, the mice were anesthetized, and blood samples were obtained from the intraorbital venous plexus. After the completion of the experiment, a histopathological analysis was performed, followed by immunohistochemical staining. At the end of the experiment, the weight of mice in the db/db + Reta group decreased, and at 10 weeks, db/db + Reta group mice had the lowest levels of body weight and food intake, followed by db/db + Tirz group and db/db + Lira group, with a statistically significant difference. These findings strongly indicate that all three drugs are effective in reducing food intake and promoting weight loss, with retatrutide demonstrating the most significant impact. Regarding HbA1c levels, retatrutide showed lower levels than those in the db/db group. In addition, the db/db + Reta group demonstrated superior efficacy in reducing alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglyceride, and low-density lipoprotein levels. Finally, after immunohistochemical analysis, retatrutide exhibited lower expression levels of inflammatory and fibrotic mediators compared to tirzepatide and liraglutide, highlighting its potential in the treatment of diabetic kidney disease.
Last but not least, Jall et al. showed a reversal of steatohepatitis in female mice by resulting in enhanced glucose tolerance, decreased body weight and fat mass, and better lipid profiles, thereby aiding in the resolution of hepatic steatosis [42]. Both female and male C57BL/6J mice at an eight-week age received a diet rich in fat and sugar. Due to differences in obesity progression between the two sexes, another cohort of male C57BL/6J mice was switched from a regular diet to a high-fat, high-sugar diet at 30 weeks of age. The mice were maintained at a temperature of 23 ± 1 °C, constant humidity, and on a 12 h light-dark cycle. After 38 weeks of age, mice were randomized within the three cohorts and equally distributed according to body composition. Mice were subcutaneously injected with the triple agonist and immediately followed by fasting for a 4 h period. Afterwards, formalin-fixed liver samples were collected. Histological analysis showed that up to 88.9% and 62.5% of female and male vehicle-treated mice, respectively, were diagnosed with definite steatohepatitis. The administration of the triple agonist resulted in the improvement of steatohepatitis in a dose-dependent fashion, with some female mice showing a complete resolution.

6. Insights from Human Studies​

6.1. Phase I Trials​

Coksun et al. in Singapore conducted a phase 1 study to assess the safety and the pharmacokinetic profile of retatrutide [35]. 47 healthy individuals entered the study, while 45 of them received at least one dose. Maximum concentration was achieved within 12–72 h after dosing. The mean half-life was about 6 days. When compared with placebo, retatrutide achieved similar changes in baseline fasting glucose levels. After dosing at 4.5 and 6 mg, mean fasting glucagon levels were decreased from 24 h post-dose up to day 15. Retatrutide achieved a decrease in mean body weight at all dose levels except at the dose of 0.1 mg. The decrease in weight was at its peak at dose levels of 3–6 mg. The most common study treatment-related adverse effects were GI disorders such as vomiting, abdominal distention, and nausea, however, mostly of mild intensity.
Following their animal studies, Urva et al. designed a phase 1b, multiple-ascending dose study in type 2 diabetic patients [40]. These patients received retatrutide once weekly (in dosage groups of 0.5, 1.5, 3, 3/6, and 3/6/9/12 mg), placebo, or 1.5 mg of dulaglutide. Retatrutide 0.5, 1.5, and 3 mg were administered for 12 weeks. The 3/6 mg group received 3 mg of retatrutide for weeks 1–4 and 6 mg for weeks 5–12. Finally, the 3/6/9/12 mg group received 3 mg for the first two weeks, 6 mg for weeks 3–4, 9 mg for weeks 5–8, and 12 mg for weeks 9–12. Gastric emptying was assessed 2 days pre-treatment and 24 h after the dose at day 2, day 30, and day 79. In summary, 72 of the participants received at least 1 dose of the drug, while 43 completed the study. The mean study age was 58.4 ± 7.4 years, mean ΒΜΙ was 32.1 ± 5.1 kg/m2, HbA1c 8.66 ± 0.92% [43]. The greatest effect on GE was found after the first retatrutide dose, while it was lower on subsequent doses, despite up-titration.

6.2. Phase II Trials​

In a phase II double-blind, randomized, placebo-controlled trial, Jastreboff et al. administered retatrutide in doses up to 8 mg for a total of 48 weeks in patients with a BMI ≥ 30 kg/m2 or with a BMI of 27–30 kg/m2 and a coexisting weight-related condition [39]. The study’s primary endpoint was the percentage change in body weight from baseline to 24 weeks of therapy. The secondary endpoints were the percentage change in body weight from baseline to 48 weeks and the presence of weight reduction in ≥5%, ≥10%, and ≥15%. 338 adults were enrolled in total. The least-squares mean percentage change in body weight at 24 weeks in the retatrutide groups was −7.2% in the 1 mg group, and up to −17.5% in the 12 mg group, as compared with −1.6% in the placebo group. Additionally, at 48 weeks, the same percentages were −8.7% in the 1 mg group, −24.2% in the 12 mg group, and −2.1% in the placebo group. At 48 weeks, a weight reduction of ≥5%, ≥10%, and ≥15% had occurred in 100%, 93%, and 83% of those who received 12 mg of retatrutide and 27%, 9%, and 2% of those who received placebo. The most common adverse effects were also gastrointestinal and dose-related and were partially mitigated with a lower starting dose (2 mg vs. 4 mg). Therefore, in adults with obesity, retatrutide treatment for 48 weeks resulted in substantial reductions in body weight.
In a similar manner, Rosenstock et al. [37] conducted a randomized, double-blind, phase 2 trial where adults aged 18–75 years with type 2 diabetes, HbA1c of 7.0–10.5%, and BMI of 25–50 kg/m2 were eligible for enrolment. Participants were treated with diet and exercise alone or with a stable dose of metformin for at least 3 months before screening. They were also randomly assigned to receive once-weekly injections of placebo, 1.5 mg dulaglutide, or retatrutide maintenance doses of 0.5 mg, 4 mg (starting dose 2 mg), 4 mg (no escalation), 8 mg (starting dose 2 mg), 8 mg (starting dose 4 mg), or 12 mg (starting dose 2 mg). The primary endpoint was a change in HbA1c from baseline to 24 weeks, and secondary endpoints included a change in HbA1c and body weight at 36 weeks. At 24 weeks, least-squares mean changes from baseline in HbA1c with retatrutide were –0.43% for the 0.5 mg group, –1.39% for the 4 mg escalation group, –1.30% for the 4 mg group, –1.99% for the 8 mg slow escalation group, –1.88% for the 8 mg fast escalation group, and –2.02% for the 12 mg escalation group, versus –0.01% for the placebo group and –1.41% for the 1.5 mg dulaglutide group. HbA1c reductions with retatrutide were significantly greater (p < 0.0001) than placebo in all but the 0.5 mg group and greater than 1.5 mg dulaglutide in the 8 mg slow escalation group (p = 0.0019) and 12 mg escalation group (p = 0.0002). Findings continued at 36 weeks. Bodyweight decreased dose-dependently with retatrutide at 36 weeks by up to 16.94% for the 12 mg escalation group, compared to 3.00% with placebo and 2.02% with 1.5 mg of dulaglutide. It was evident that retatrutide showed clinically meaningful improvements in glycaemic control and impressive reductions in body weight in type 2 diabetic patients while being relatively safe.
Another phase II trial by Sanyal et al. [44] attempted to show retatrutide’s effects on liver steatosis. 98 patients having ≥10% liver fat content (as defined by magnetic resonance imaging proton density fat fraction) were randomly assigned to 48 weeks of once-weekly subcutaneous retatrutide (1, 4, 8, or 12 mg dose) or placebo. In total, 76 participants managed to complete this substudy. The mean relative change from baseline in liver fat at 24 weeks was −42.9% (1 mg), −57.0% (4 mg), −81.4% (8 mg), −82.4% (12 mg), and +0.3% (placebo). At 24 weeks, normal liver fat (<5%) was achieved by 27% (1 mg), 52% (4 mg), 79% (8 mg), 86% (12 mg), and 0% (placebo) of participants. At 48 weeks, the mean relative change from baseline in liver fat was −51.3% (1 mg), −59.0% (4 mg), −81.7% (8 mg), −86.0% (12 mg), and −4.6% (placebo). Additionally, total liver fat content < 5% at 48 weeks was achieved with 8 mg (in 89% of participants) and 12 mg doses (in 93% of participants). Liver fat reduction was associated with weight loss, abdominal fat, and improved insulin sensitivity and lipid metabolism.

7. The Future—Phase III Trials​

The promising results of the above trials led to the design of the first phase III trials for retatrutide—the TRIUMPH trials, where the efficacy and safety of retatrutide in participants who are obese or overweight will be evaluated. The first trial—TRIUMPH 1 is estimated to last until May 2026, and it aims to enrol 2300 patients [45].
The TRIUMPH-2 trial will evaluate the efficacy and safety of retatrutide in participants with T2DM who are obese or overweight, including a subset of participants who have obstructive sleep apnea (OSA). It aims to enrol 1000 patients, and it will last about 89 weeks with an expected due date of May 2026.
Another Phase III Trial—TRIUMPH 3 aims to investigate the per cent change from baseline in body weight in obese individuals with established cardiovascular disease (i.e., prior myocardial infarction). Participants must have excess weight, a history of heart attack, stroke, or presence of peripheral arterial disease, and also a history of at least 1 self-reported unsuccessful dietary effort to reduce body weight in order to meet the eligibility criteria. Patients will be excluded (1) if they have had a heart attack, stroke, hospitalization for congestive heart failure or unstable angina within 90 days before screening, (2) if they have been taking any weight loss drugs, including over-the-counter medications, within 90 days before screening, (3) if they have had a change in body weight greater than 11 pounds within 90 days, (4) if they have or are planning a surgical treatment for excess weight, (5) if they have Type 1 Diabetes Mellitus, (6) if they have a family or personal history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN-2) and (7) if they have had pancreatitis. The trial is expected to be completed in February 2026 with an enrolment goal of 1800 patients.
Finally, the TRIUMPH-4 study will assess the subset of obese or overweight participants with concomitant knee osteoarthritis, after being treated with retatrutide. It has an enrolment goal of 405 patients, and it is estimated to last until December 2025.
The planning and execution of additional phase III studies could offer in-depth insights into the critical factors influencing weight reduction. It is vital to understand that achieving weight loss is not always beneficial for health; in certain circumstances, it may lead to clinically significant declines in muscle and bone mass rather than a target reduction in fat. This phenomenon raises important questions about the quality and composition of weight loss, as retaining lean body mass is essential for maintaining overall strength, mobility, and metabolic health. Therefore, there is a need to design studies that not only focus on the percentage but also investigate the body composition changes that accompany weight loss [46,47,48,49].
It should be noted, however, that while retatrutide shows promise as a weight-loss therapy for adults, its use is not currently approved for children and adolescents. The safety and efficacy of retatrutide have not been established in pediatric populations. Current clinical trials have focused exclusively on adults, and there is a lack of data regarding its use in children and adolescents. Therefore, retatrutide is not indicated for individuals under 18 years of age. For children and adolescents, obesity prevention and management should prioritize non-pharmacological interventions. Lifestyle modifications, including a balanced diet and regular physical activity, are the cornerstone of pediatric obesity prevention. The U.S. Preventive Services Task Force recommends that clinicians screen for obesity in children and adolescents aged 6 years and older and offer or refer them to comprehensive, intensive behavioural interventions to promote improvements in weight status [50].

8. Conclusions​

In conclusion, retatrutide appears to herald a significant advancement in the realm of pharmacotherapy for obesity and weight management (Figure 2). With its remarkable safety profile and noteworthy percentages of weight reduction, it undeniably generates considerable enthusiasm within the medical community. However, it is essential to emphasize that additional phase 3 clinical trials are crucial to further evaluate the drug’s safety and long-term effects.

Figure 2.​

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The present and future of Retatrutide.
Moreover, the financial implications of this groundbreaking medication cannot be ignored; despite its promising attributes, it may remain an inaccessible option for patients who cannot afford such treatments. Furthermore, studies assessing the quality of weight loss beyond simple BMI reduction are lacking, underscoring a significant area that warrants deeper research. This gap highlights the need for comprehensive studies that evaluate not only the effectiveness of weight loss but also its overall impact on patients’ health and well-being.

Interesting article. Are you guys on a trial study or are you ordering Retatrutide?

 

Interesting article. Are you guys on a trial study or are you ordering Retatrutide?

We order it. I would love to be a part of a trial however... free stuff

 

We order it. I would love to be a part of a trial however... free stuff

What dose did you start at to experience that amount of weight loss in 2 weeks? Any other sides, such as low energy, brain fog, or insomnia? How are things now that you are farther out with the med?

 

What dose did you start at to experience that amount of weight loss in 2 weeks? Any other sides, such as low energy, brain fog, or insomnia? How are things now that you are farther out with the med?

I started with 1mg, which is a low dose. I have had unpleasant experiences with other GLP-1 drugs, so I wanted to start slow. After a week, I bumped it to 2 mg and have been on that dosage since. I'm going to go to 3 mg on my next injection.

I did feel the low energy side effects at first, but they have since cleared. No insomnia or brain fog.

The weight loss is amazing. I haven't weighed myself in a few weeks, but my pants were falling off of me, and I am now back in a size 34. Added benefits are a decrease in cravings and appetite. My wine consumption has decreased, which is a good thing

 

I started with 1mg, which is a low dose. I have had unpleasant experiences with other GLP-1 drugs, so I wanted to start slow. After a week, I bumped it to 2 mg and have been on that dosage since. I'm going to go to 3 mg on my next injection.

I did feel the low energy side effects at first, but they have since cleared. No insomnia or brain fog.

The weight loss is amazing. I haven't weighed myself in a few weeks, but my pants were falling off of me, and I am now back in a size 34. Added benefits are a decrease in cravings and appetite. My wine consumption has decreased, which is a good thing

Thanks for this info I appreciate it. I'm considering reta over tirz. Since I'm pushing 60 just looking for a little extra nutrition partitioning and fat burning. From what I've seen reta seems to be great at this. And from what I've read and it works synergistically with TRT and HGH or secretagouges. I appreciate it

 

wife had amazing results, 60lb in 8 months or so. very few GI issues. the glucagon part of reta gives me some anxiety/insomnia unfortunately. at any dose. i need to lose like 20lb. i got here without glp's but a small appetite suppression is nice. not sure if i want to try tirz again, or just discipline and/or maybe a short sprint keto. i dont like keto but it works. i also don't gain any fat, so might use keto to get to goal and revert to my current diet

 

wife had amazing results, 60lb in 8 months or so. very few GI issues. the glucagon part of reta gives me some anxiety/insomnia unfortunately. at any dose. i need to lose like 20lb. i got here without glp's but a small appetite suppression is nice. not sure if i want to try tirz again, or just discipline and/or maybe a short sprint keto. i dont like keto but it works. i also don't gain any fat, so might use keto to get to goal and revert to my current diet

Yeah I think I saw some of your other posts on reta and the insomnia bit. I thought that was interesting I hadn't really seen a lot of that. Is that side effect dose dependent for you? Or is it regardless

 

Yeah I think I saw some of your other posts on reta and the insomnia bit. I thought that was interesting I hadn't really seen a lot of that. Is that side effect dose dependent for you? Or is it regardless

any dose, even at 200mcg. i think reta is really nice otherwise i would highly recommend. you can get it for like 1usd/1mg even you shop around

 

Here it's more like 13E/mg. Anyone knows a reliable supplier within the EU?

 

I just switched from Terzepitide 1.25mg every 5 days after being on for a year and now 0.5mg Retatrutide every other day and think my mind is more clear and increased energy. I am 13.3% body fat 63 in decent shape mainly want glucose control post meal. I like to be able to eats some carbs and have it back to base of 85 in 90 minutes. GLP's really help and all I hear about Reta is it is even better. More to come after a month or two in this.

 

Retatrutide has a halflife of 5 days. Do you notice it? Would twice weekly be better?

 

This stuff burns fat like Napalm... I have never lost weight this fast before. It's also quite a bit different from the other GLP-1 drugs regarding appetite control, it removes the cravings. It also changes your taste a bit. I am a wine enthusiast (read that as wino). Admittedly, I drink too much of it. This has cut that in half as I just don't crave it as much.

 

Retatrutide has a halflife of 5 days. Do you notice it? Would twice weekly be better?

Once a week is working for me, I haven't really noticed any kind of wearing off effects.

 

Your thread motivated me to look again for a source. Hope I got real Reta. I have started yesterday with 1mg.

 

1mg at once. Second day constipation.

 

1mg at once. Second day constipation.

Both semaglutide and tirzepatide did that to me, but surprisingly not retatrutide. Hopefully it will pass (no pun intended)

 

Both semaglutide and tirzepatide did that to me, but surprisingly not retatrutide. Hopefully it will pass (no pun intended)

I'm sort of a highly sensitive person. So, if someone is in the same boat, better start with 0.5mg.

 

Did you change your nutrition or meal portions?
Do you supplement with carnitine?

 

Did you change your nutrition or meal portions?
Do you supplement with carnitine?

I haven't changed anything nutritionally as I already eat a balanced high protein diet. Portion size is smaller because you get full faster. I would imagine if you were doing Keto the results would be even greater, but I love bread too much to do it for any length of time. I don't eat a lot, but my English Muffin in the morning with coffee is something I am not giving up.

I do supplement with a combo of ALC and ALA, I have been taking that for years.