Glossary
Retatrutide
Updated March 29, 2026
Retatrutide is an investigational triple-receptor agonist (GLP-1, GIP, and glucagon) currently in Phase 3 clinical trials (TRIUMPH program). It targets three hormone pathways involved in appetite regulation and energy metabolism. In Phase 2 trials, participants on the 12mg dose lost an average of 24.2% body weight over 48 weeks, the largest reduction seen in any obesity medication trial to date. For people who train, retatrutide's aggressive appetite suppression demands the most structured approach to protein, fueling, and training of any medication in this class. For the medication-specific protein and lifting setup, read Protein Targets and Training Strategy on Semaglutide or Retatrutide.
Research identifiers
| Name | What it refers to |
|---|
| Retatrutide | generic development name used in trial reporting |
| LY3437943 | Eli Lilly development code used in research and trial registries |
Status and access
| Item | Current state |
|---|
| Regulatory status | investigational, access limited to clinical trials (Phase 3 as of early 2026) |
| Manufacturer | Eli Lilly |
| Phase 3 focus areas | obesity, type 2 diabetes, cardiovascular outcomes, osteoarthritis |
| Expected timeline | FDA submission anticipated based on Phase 3 results |
How retatrutide differs from tirzepatide and semaglutide
| Factor | Retatrutide | Tirzepatide | Semaglutide |
|---|
| Receptor targets | GLP-1 + GIP + glucagon (triple) | GLP-1 + GIP (dual) | GLP-1 (single) |
| Appetite suppression | strongest in trials to date | very strong | strong |
| Weight loss in trials | 24.2% at 48 weeks (Phase 2, 12mg) | 22.5% at 72 weeks (15mg) | 15-17% at 68 weeks (2.4mg) |
| Glucagon receptor activation | yes (increases energy expenditure and hepatic fat metabolism) | no | no |
| Under-fueling risk | highest of all three | high | moderate |
| Dosing | weekly injection | weekly injection | weekly injection or daily tablet |
Physique-first planning model
| Goal | What to emphasize | Specific targets | What to avoid |
|---|
| Fat loss with muscle retention | moderate deficit, high protein, consistent lifting | 15-20% deficit (300-400 cal/day, more conservative than other GLP-1s), 1.4-1.6 g/kg protein, 3-4 lifting sessions per week | rapid loss exceeding 1.5 lb per week, which is more likely on retatrutide than on other medications |
| High-output training blocks | carbs placed around sessions, stable hydration | 30-50g carbs pre-workout, 64-80 oz water + electrolytes daily, keep total intake near maintenance | skipping recovery meals because appetite is nearly absent |
| Long-term sustainability | simple meal templates and micronutrient coverage | 3-4 structured meals daily with protein anchor at each, daily multivitamin as insurance given reduced food volume | turning the plan into a daily negotiation with your appetite |
Nutrition and training guardrails
| Guardrail | Specific target | Practical examples | Expected signal |
|---|
| Protein floor | 1.4-1.6 g/kg daily, 30-40g per meal (higher floor than other GLP-1s due to strongest suppression) | 5 oz chicken breast (~44g), 6 oz salmon (~34g), 1 cup cottage cheese (~28g), protein shake + Greek yogurt (~45g) | better strength retention and fewer flat sessions |
| Training consistency | maintain progressive overload, reduce volume before skipping days | squat, bench, row, deadlift or close variations, 3-4 sessions per week | physique quality holds as weight trends down |
| Hydration and electrolytes | 64-80 oz daily, plus 16-20 oz per hour of training, add sodium on heavy sweat days | 32 oz bottle x2 before dinner, electrolyte tab or pinch of salt during sessions | fewer headaches and less dizziness |
| Micronutrient density | prioritize nutrient-dense meals as total food volume drops | choose whole foods over processed options at each meal, consider a daily multivitamin | better energy and fewer low-intake side effects |
| Fiber ramp | 25-30g daily, increase by 3-5g per week | 1/2 cup lentils (~8g), 1 oz chia seeds (~10g), 1 cup broccoli (~5g) | better digestion without GI backlash |
Training integration on retatrutide
The glucagon receptor activation in retatrutide increases resting energy expenditure, which means your body burns more at rest but also depletes faster during training. Pre-workout fueling is critical.
| Training context | Pre-workout nutrition (60-90 min before) | Post-workout nutrition (within 2 hours) | Adjustment cues |
|---|
| Standard session | 30-50g carbs + 20g protein (oatmeal + protein shake, banana + Greek yogurt) | 35-40g protein + 30-40g carbs (chicken + rice + vegetables) | if sessions feel flat for 2+ workouts, increase pre-workout carbs by 15-20g |
| Low-appetite day | minimum 20g carbs + 15g protein (rice cake + peanut butter, half banana + protein shake) | 30g protein in any format you can tolerate | reduce volume by 1-2 sets rather than skipping |
| High-output session | 40-60g carbs + 25g protein, 90 min before | 40-50g protein + 40-50g carbs within 90 min | leg and back days carry the highest under-fueling risk |
Body composition monitoring
Retatrutide's aggressive weight loss trajectory makes monitoring essential. Weight can drop fast enough that muscle loss is hidden inside what looks like successful fat loss.
| What to track | How to measure | Frequency | Decision rule |
|---|
| Weight trend | morning weigh-in under same conditions, 14-day rolling average | daily weigh-in, weekly trend review | losing more than 1.5 lb per week consistently warrants immediate intake audit |
| Waist and hip circumference | fabric tape at navel and widest hip point | every 2 weeks | waist dropping while weight is stable suggests recomposition |
| Strength in core lifts | track top sets in squat, bench, row, or deadlift | every session | any strength decline across 2+ weeks means raise intake first |
| Limb circumference | mid-bicep and mid-thigh with fabric tape | every 2 weeks (more frequent than other medications) | large drops are a red flag for lean mass loss |
| Progress photos | same lighting, time of day, and poses | every 2 weeks | visual check against rapid changes |
Safety and escalation thresholds
| Signal pattern | Why it matters | Next step |
|---|
| Severe abdominal pain with persistent vomiting | pancreatitis or gallbladder complication risk | urgent clinical evaluation |
| Persistent dehydration signs or inability to keep fluids down | kidney and electrolyte stress risk | seek medical guidance |
| Severe weakness, confusion, or fainting | systemic risk | urgent evaluation |