Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. GLP-1 receptor agonists are prescription medications — any changes to your training program, nutrition, or medication dose should be discussed with your prescribing provider. Individual responses to these drugs vary significantly.
Training & Performance
HOW TO TRAIN ON GLP-1 DRUGS
Your appetite is down 40%. Your calories are down 30%. You cannot train the same way. Here is how to adjust your programming to preserve muscle, maintain strength, and get the most out of the drug.
Medically reviewed by Missy Zammichieli, DNP, APRN, FNP-BC · Updated March 25, 2026
WHY TRAINING CHANGES ON GLP-1s
GLP-1 drugs work primarily by suppressing appetite. That is the mechanism. You eat less. For most patients, caloric intake drops 25-40% — often without trying. That is a significant caloric deficit, and a caloric deficit changes everything about how your body responds to training.
When you are eating 1,200-1,600 calories instead of 2,200-2,800, your recovery capacity shrinks. You cannot repair the same amount of muscle damage. You cannot replenish glycogen as fast. Your nervous system takes longer to recover from heavy loads. The training that built your fitness on a maintenance or surplus diet is now more than your body can recover from on a 30% deficit.
This is where most people on GLP-1s make one of two mistakes:
Mistake #1: Training the Same Way
They keep the same volume, same frequency, same intensity. Their body cannot recover. Performance tanks. They feel terrible. Joints hurt. Sleep suffers. They conclude the drug doesn't work or that exercise is pointless on it. Neither is true — they are just under-recovered and over-trained relative to their new caloric intake.
Mistake #2: Stopping Training
They feel low energy, the scale is moving, and they figure the drug is doing the work. So they stop lifting. This is the bigger mistake. Without resistance training, up to 40% of the weight you lose can be lean mass — muscle, bone density, metabolic tissue. You lose the weight but come out the other side metabolically worse: lower resting metabolic rate, less muscle, weaker, and primed to regain everything.
The correct approach: Adjust your training to match your new recovery capacity. Reduce volume. Maintain intensity. Prioritize compound movements. Protect your protein intake. This is not complicated — but it does require deliberate programming changes, not just "doing less."
THE NON-NEGOTIABLES
Before we get into programming details, there are two things that are not optional. If you skip either one, you will lose muscle, and no amount of clever programming will save you.
Resistance Training 3-4x/Week
Compound movements. Squats, deadlifts, presses, rows, pull-ups. Heavy enough to be challenging (RPE 7-8). This is the primary signal that tells your body to keep muscle tissue while shedding fat. Without this signal, your body will catabolize muscle right alongside fat.
Three sessions per week is the minimum effective dose. Four is better if you can recover from it. Two is not enough to preserve lean mass in a significant caloric deficit. Five or more is almost certainly too much on a GLP-1.
Protein: 1g Per Pound of Ideal Body Weight
Every single day. Not "most days." Not "when I feel like eating." This is the hardest non-negotiable on a GLP-1 because the drug is actively suppressing your appetite, and protein-rich foods are often the hardest to get down when you feel full.
If your ideal body weight is 170 lbs, you need 170g of protein daily. That is approximately 680 calories from protein alone. When your total daily intake might be 1,400 calories, protein needs to represent nearly half your diet. Plan accordingly or you will under-eat protein every day.
Why these two specifically? Research on caloric restriction consistently shows that the combination of resistance training and high protein intake is the most effective strategy for preserving lean mass during weight loss. Neither alone is sufficient. A 2022 meta-analysis in Sports Medicine found that resistance exercise combined with high protein intake (~1.6g/kg/day) preserved significantly more lean mass during energy deficit compared to either intervention alone.
PROGRAMMING ADJUSTMENTS
Here is how to modify your existing program. These adjustments assume you already train with some form of structured resistance programming. If you do not currently train, start with a simple 3-day full-body program using the compound movements listed below.
Volume: Reduce 15-20% Initially
If you normally do 5 sets of squats, drop to 4. If you normally hit 16 total working sets per session, bring it to 12-13. The goal is to reduce the total amount of muscle damage per session so your under-fueled body can actually recover from it.
Crucially, maintain the weight on the bar. Intensity (load) is the primary muscle-preservation stimulus. Volume (total sets and reps) is the recovery cost. When recovery is limited, cut the cost — not the stimulus.
Practical rule: if you are adding sets to "make up" for eating less, you have it backwards. Less fuel means less volume, not more.
Frequency: 3-4 Days Per Week
Three to four resistance training sessions per week, built around compound movements. This gives you enough frequency to stimulate muscle protein synthesis regularly (the anabolic window from a resistance session lasts roughly 24-48 hours) while leaving enough recovery days to adapt.
If you were training 5-6 days per week before starting the drug, drop to 4 and reassess after 3-4 weeks. If recovery is solid — meaning you are hitting the same weights, sleeping well, and not accumulating fatigue — you can try adding back a session. If you are grinding, drop to 3.
Exercise Selection: Compounds Over Isolation
When training economy matters, every exercise needs to earn its spot. Compound movements train multiple muscle groups per exercise, giving you maximum stimulus for minimum recovery cost.
Prioritize
- Squat variations (back squat, front squat, goblet squat)
- Deadlift variations (conventional, trap bar, RDL)
- Pressing (bench press, overhead press, dumbbell press)
- Rowing (barbell row, dumbbell row, cable row)
- Pull-ups / lat pulldowns
- Lunges / step-ups
Deprioritize
- Bicep curls, tricep kickbacks
- Lateral raises, front raises
- Leg extensions, leg curls
- Cable crossovers, pec deck
- Calf raises
- Any machine isolation work
This does not mean isolation work is bad. It means that when your total recovery budget is limited, you should spend it on the movements that train the most muscle mass per set. If you have energy and recovery capacity left over after your compound work, add isolation. But the compounds are the priority.
Conditioning: Scale Intensity, Keep the Engine Running
Cardiovascular conditioning still matters on a GLP-1. It supports heart health, improves insulin sensitivity, and helps with the psychological side of weight loss. But you have to be strategic about it.
Scale intensity before volume. A 30-minute moderate-effort session (Zone 2 heart rate, conversational pace) costs far less recovery than a 15-minute all-out interval session. On a caloric deficit, that recovery cost matters.
Two to three conditioning sessions per week is reasonable. Keep at least one as steady-state Zone 2 work (walking, cycling, rowing at conversational pace). If you include a higher-intensity session, keep it short (12-15 minutes) and on a day you are not also doing heavy lifting.
Do not redline under-fueled. A 1,400-calorie day followed by a max-effort Assault Bike sprint session is a recipe for feeling terrible and recovering poorly. Keep the engine running. Do not blow it up.
Deload Triggers
On a standard training program, you might deload every 4-6 weeks. On a GLP-1, you need more responsive triggers because your recovery capacity fluctuates based on how well you are eating that week.
Deload Your Next Session If:
- • You missed 2+ meals in a day (caloric intake was significantly below target)
- • You had significant GI side effects in the previous 24-48 hours
- • Your sleep has been under 6 hours for 2+ consecutive nights
- • Your working weights feel RPE 9-10 when they should feel 7-8
- • You are in the first 1-2 weeks of a new dose escalation
A deload session means: same exercises, same movement patterns, but at 60-70% of your normal working weight for the same rep scheme. You still go to the gym. You still move. You just take the intensity down so your body can catch up.
NUTRITION TIMING ON GLP-1s
When total calories are low, when you eat becomes more important. You cannot afford to waste your limited appetite on the wrong meals at the wrong times.
Pre-Training: Your Biggest Meal
Eat your largest meal 2-3 hours before training. This is when you want the most fuel available. Prioritize protein (40g+) and carbohydrates (the fuel for resistance training). This meal should be the one you plan your day around — not an afterthought.
Liquid Protein When Solid Food Is Hard
GLP-1 drugs slow gastric emptying. Some days, solid food feels like eating concrete. This is normal, especially during dose escalation. On those days, liquid protein sources are your safety net: whey protein shakes, clear protein drinks (collagen-based), bone broth, Greek yogurt smoothies. The protein still counts. Getting 40g of protein from a shake is infinitely better than getting 0g because you could not face a chicken breast.
Leucine Threshold: 2.5-3g Per Meal
Leucine is the amino acid that triggers muscle protein synthesis (MPS). You need approximately 2.5-3g of leucine per meal to cross the threshold and "turn on" MPS. This typically corresponds to 30-40g of high-quality protein per meal. If you are only eating 2-3 meals per day on a GLP-1 (common), each one needs to hit this threshold. Spreading 100g of protein across five 20g mini-meals is less effective than concentrating it into three 33g meals that each clear the leucine gate.
Post-Training Window
The "anabolic window" is less narrow than old gym lore suggests, but on a GLP-1 it matters more than usual. Your body is in a deficit and has just experienced training stress. Get 30-40g of protein within 1-2 hours post-training. If you cannot stomach solid food after training, this is a good time for a protein shake.
HYDRATION & ELECTROLYTES
GLP-1 drugs increase fluid loss through multiple mechanisms: reduced food intake (food provides 20-30% of daily water intake for most people), GI side effects (nausea, diarrhea, vomiting during dose escalation), and increased urinary output as the body mobilizes stored glycogen and fat.
Dehydration compounds every negative effect of caloric restriction on training performance: worse strength output, slower recovery, increased muscle cramping, impaired cognitive function, and elevated heart rate during conditioning work.
Sodium
2,000-3,000mg Extra Per Day
You are eating less food, which means less dietary sodium. Add it back deliberately. Salt your food aggressively. Consider an electrolyte drink with 500-1,000mg sodium per serving before and during training. Low sodium is the most common cause of headaches, dizziness, and weakness on GLP-1s that gets misattributed to the drug itself.
Potassium
300-500mg Supplemental
Critical for muscle contraction and heart function. Reduced food intake means reduced dietary potassium. Good sources: avocado, potato, banana, spinach. If food intake is very low, a potassium supplement (potassium citrate) can fill the gap. Do not mega-dose — excess potassium can cause cardiac issues.
Magnesium
200-400mg Glycinate or Citrate
Involved in 300+ enzymatic processes including muscle contraction, sleep quality, and recovery. Most Americans are already mildly deficient. On a GLP-1, the deficit gets worse. Magnesium glycinate is well-tolerated (magnesium oxide is cheap but poorly absorbed and can worsen GI symptoms). Take before bed — it also supports sleep.
Minimum daily water: Half your body weight in ounces, plus 16-24 oz for every hour of training. On a GLP-1, you likely need even more than this. If your urine is dark yellow, you are behind. If you are getting muscle cramps during training, start with electrolytes before blaming the workout.
CROSSFIT-SPECIFIC CONSIDERATIONS
Moonshot Medical and Moonshot CrossFit share a building. This is not a coincidence. Our providers prescribe GLP-1 drugs on one side of the wall, and our coaches program training on the other. Here is what that coordination looks like in practice.
CrossFit Is Actually Well-Suited for GLP-1 Patients
A typical CrossFit session includes strength work (squats, deadlifts, presses) plus conditioning (a "metcon" — metabolic conditioning workout). This maps directly onto what GLP-1 patients need: compound resistance training plus cardiovascular work. You do not need to abandon CrossFit. You need to scale it.
Scale the Metcon, Keep the Strength
The strength portion of class is your highest priority. Hit the prescribed weight (or close to it). Do the full sets. This is the muscle-preservation signal.
The metcon is where you scale. Reduce the intensity (lighter weight, fewer reps, slower pace) rather than the movement patterns. If the workout calls for 21-15-9 thrusters and pull-ups, scale to 15-12-9 at a lighter weight rather than skipping the workout. You want the cardiovascular stimulus at a dose your body can recover from.
Communicate with Your Coach
Tell your coach you are on a GLP-1. This is not sensitive information in a gym setting — it is training-relevant information, like telling your coach you have a sore shoulder. Your coach can help you scale appropriately, flag when you look like you are pushing too hard, and program around your recovery limitations. If your coach and your provider are in the same building (as they are at Moonshot), they can coordinate directly.
Class Frequency
Three to four classes per week is the target. If your gym runs daily classes, you do not need to attend all of them. Pick the days with programming that aligns with your priorities (heavy strength days over high-volume conditioning days). Use off days for walking, mobility work, or light active recovery — not more high-intensity work.
RETATRUTIDE SPECIFICALLY
Everything above applies to all GLP-1 receptor agonists — semaglutide (Ozempic/Wegovy), tirzepatide (Mounjaro/Zepbound), and retatrutide. But retatrutide has a unique feature that may change the training equation: the glucagon receptor.
Retatrutide is a triple agonist — it activates GLP-1, GIP, and glucagon receptors simultaneously. The glucagon component is the differentiator. Glucagon stimulates hepatic fat oxidation and increases resting energy expenditure (REE). In the Phase 2 trial, this appeared to increase the total calories burned at rest.
What this means for training: if retatrutide is genuinely increasing your resting metabolic rate, you may be able to sustain a meaningful rate of fat loss while eating slightly more than you would on semaglutide or tirzepatide alone. A smaller caloric deficit means more recovery capacity. More recovery capacity means you can potentially maintain closer to your pre-drug training volume.
Important caveat: This is based on Phase 2 mechanistic data. Phase 3 trials are ongoing. We do not yet have direct evidence quantifying how much retatrutide's glucagon activity changes resting energy expenditure in a clinical population, or how that translates to training recovery. The practical recommendation: start with the same conservative adjustments as any other GLP-1, then titrate training volume up if your recovery allows it and your DEXA scans confirm you are maintaining lean mass.
The glucagon component may also have implications for lean mass preservation directly. Preclinical data suggests glucagon receptor activation may help partition energy expenditure toward fat oxidation and away from muscle catabolism. If confirmed in Phase 3 data, retatrutide could be the first GLP-1 class drug where training volume does not need to drop as much. But we are not there yet.
WHEN TO ADJUST THE DOSE — NOT THE TRAINING
This is the most counterintuitive piece of advice in this guide, and the most important: if you are losing lean mass on a GLP-1, the answer is usually to lower the drug dose — not cut your training.
Most providers titrate GLP-1 doses based on weight loss rate and side effect tolerance. That is reasonable, but it misses a critical variable: body composition. The scale might be dropping at a "good" rate, but if DEXA scans show that 30% of the loss is lean mass, you are losing too fast and losing the wrong tissue.
The priority hierarchy should be:
Resistance Training — Non-Negotiable
This stays. 3-4x per week, compound movements, RPE 7-8. If anything gets cut, it is not this.
Protein Intake — Non-Negotiable
1g per pound ideal body weight. If you are struggling to hit this, use liquid protein sources. Do not just accept a protein deficit.
Drug Dose — The Variable
If lean mass is dropping on DEXA despite good training adherence and protein intake, discuss a dose reduction with your provider. A slower rate of total weight loss with better body composition (mostly fat loss) is a superior outcome to rapid weight loss that includes significant muscle.
This is why DEXA matters. A scale tells you that you lost 15 pounds. A DEXA scan tells you that 12 pounds was fat and 3 pounds was muscle — or that 9 pounds was fat and 6 pounds was muscle. Those are completely different outcomes that require completely different interventions. You cannot manage what you cannot measure.
SAMPLE TRAINING WEEK
This is a template, not a prescription. Adjust based on your training history, schedule, and recovery. The structure matters more than the specific days.
Back Squat: 4x5 @ RPE 7-8. Overhead Press: 4x6 @ RPE 7-8. Walking Lunges: 3x10/leg. Plank holds: 3x30-45 sec. Total session: ~45 minutes.
25-30 minutes Zone 2: row, bike, or brisk walk. Keep heart rate conversational. This is recovery-friendly cardio — not a race. If you feel good, finish with 3 rounds of: 10 kettlebell swings + 10 box step-ups at easy pace.
Walk 20-30 minutes. Foam roll. Stretch. This is a rest day — honor it. If you feel like you "should" be doing more, remind yourself that recovery is when adaptation happens. You are on a caloric deficit. Your body needs this.
Trap Bar Deadlift: 4x5 @ RPE 7-8. Barbell Row: 4x8 @ RPE 7. Pull-ups or Lat Pulldown: 3x8-10. Farmer Carries: 3x40m. Total session: ~45 minutes.
Goblet Squat: 3x10. Dumbbell Bench Press: 3x10. Dumbbell RDL: 3x10. Then: 12-minute AMRAP at moderate pace — 200m row, 10 push-ups, 10 ring rows. Scale the conditioning to feel like a 6/10 effort, not a 9/10.
Walk, hike, bike ride, yoga, mobility work. Move your body at low intensity. Do not add another training session here unless your recovery is genuinely solid after 4+ weeks on this schedule and your DEXA shows lean mass is stable.
COMMON QUESTIONS
Can I do CrossFit on GLP-1 drugs?
Yes. CrossFit is actually well-suited for GLP-1 patients because it combines resistance training with conditioning — both of which you need. The key is scaling appropriately: keep the strength work heavy (RPE 7-8), scale metcon intensity before cutting volume, and communicate with your coach about your medication and recovery status. At Moonshot, our gym and clinic share a wall, so your coach and provider can coordinate directly.
Will I lose strength on GLP-1 drugs?
Some strength loss is possible during the initial adjustment period, particularly if your caloric intake drops significantly. However, maintaining heavy compound lifts at RPE 7-8 (even with reduced volume) and hitting 1g protein per pound of ideal body weight will minimize strength losses. Most patients who follow a structured resistance training program maintain or even improve their strength-to-bodyweight ratio as they lose fat.
How much protein do I need on GLP-1 drugs?
Aim for 1 gram of protein per pound of your ideal body weight, every day. This is non-negotiable. On a GLP-1 drug, your appetite is suppressed and total calories are down — which means the protein you do eat becomes even more critical for muscle preservation. Each meal should contain at least 30-40g of protein with 2.5-3g of leucine to trigger muscle protein synthesis. If solid food is difficult, liquid protein (whey shakes, bone broth, clear protein drinks) counts.
Should I cut my training on GLP-1 drugs?
Reduce volume, not intensity. Cut total weekly sets by 15-20% initially, but keep the weight on the bar heavy (RPE 7-8). Drop accessory and isolation work before cutting compound lifts. If you are missing meals or feeling run down, deload that session rather than skipping it entirely. The worst thing you can do on a GLP-1 drug is stop training — resistance training is the single most important lever for preserving muscle mass during weight loss.
Can I build muscle on retatrutide?
Building significant new muscle mass while in a caloric deficit is unlikely for trained individuals, regardless of the drug. The realistic goal on any GLP-1 medication is muscle preservation — keeping the muscle you have while losing fat. That said, retatrutide's glucagon component may increase resting energy expenditure, which could allow for a smaller caloric deficit at the same rate of weight loss. A smaller deficit means more recovery capacity and a better environment for maintaining (and in some cases marginally increasing) lean mass. DEXA scans are the best way to track this.
References
- 1. Jastreboff AM, et al. "Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial." N Engl J Med. 2023;389(6):514-526.
- 2. Coskun T, et al. "LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss." Cell Metab. 2022;34(9):1234-1247.
- 3. Murphy CH, et al. "Dietary Protein to Maintain Muscle Mass in Aging: A Case for Per-meal Protein Recommendations." J Frailty Aging. 2016;5(1):49-58.
- 4. Morton RW, et al. "A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults." Br J Sports Med. 2018;52(6):376-384.
- 5. Wilding JPH, et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity." N Engl J Med. 2021;384(11):989-1002. (STEP 1)
- 6. Jastreboff AM, et al. "Tirzepatide Once Weekly for the Treatment of Obesity." N Engl J Med. 2022;387(3):205-216. (SURMOUNT-1)
- 7. Hector AJ, Phillips SM. "Protein Recommendations for Weight Loss in Elite Athletes: A Focus on Body Composition and Performance." Int J Sport Nutr Exerc Metab. 2018;28(2):170-177.
- 8. Churchward-Venne TA, et al. "Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men." Am J Clin Nutr. 2014;99(2):276-286.
TRAINING + MEDICAL OVERSIGHT UNDER ONE ROOF
Moonshot Medical prescribes the drug. Moonshot CrossFit programs the training. DEXA tracks the results. Your provider and your coach talk to each other — because losing 40 pounds of fat while keeping your muscle is a team effort.