Let me introduce you to Marcus.
He's 52, started semaglutide three months ago, and the weight is coming off. His doctor is pleased. His clothes fit differently. By every headline metric, it's working.
But Marcus is exhausted. He's losing his appetite entirely by 3pm, skipping meals because nothing sounds good, and his gym sessions feel harder than they used to. He assumed the medication was doing the heavy lifting — so he stopped thinking as hard about food.
Here's what nobody told Marcus: the medication opens the door. What you eat determines what happens once you walk through it.
The Part Nobody Talks About Loudly Enough
GLP-1 receptor agonists — Ozempic, Wegovy, Mounjaro, Zepbound — work by slowing how quickly food leaves your stomach, suppressing appetite, and regulating blood sugar. The results can be genuinely transformative.
But there's a finding buried in the clinical data that deserves a lot more attention.
Research from the STEP-1 trial, published in the New England Journal of Medicine, found that approximately 39% of weight lost on semaglutide came from lean mass — not just fat. A 2025 study presented at ENDO, the Endocrine Society's annual meeting, found that women and older adults on semaglutide were at particularly high risk for this muscle loss — and that higher protein intake was one of the most effective ways to counter it. A separate prospective 6-month study of 200 adults on semaglutide or tirzepatide found that those who followed resistance training and adequate protein guidance lost around 13% of their body weight but only 3% of their muscle mass — a dramatically better outcome than medication alone.
The takeaway is not that GLP-1s are dangerous. It's that they are a tool, and like any powerful tool, what you do alongside them determines the outcome. Eating intentionally while on a GLP-1 isn't optional — it's what separates a body composition transformation from simply getting smaller.
The Three Non-Negotiables on a GLP-1
1. Protein — aim for 100g per day
When your appetite is suppressed and you're eating significantly less food, the risk of protein deficiency is real and consequential. Muscle loss slows metabolism, weakens bones, reduces insulin sensitivity, and makes it harder to maintain results if you ever reduce or stop the medication.
Current evidence supports a target of 1.2–1.6g of protein per kilogram of body weight for people on GLP-1 therapy. For most adults, this lands in the range of 100g per day — and it needs to be distributed across meals, not loaded into one sitting.
What that actually looks like in food:
FoodProtein4 oz grilled salmon~25g¾ cup Greek yogurt (plain, full-fat)~17g2 large eggs~12g½ cup cottage cheese~14g½ cup edamame~9g3 oz roasted chicken breast~26g½ cup lentils (cooked)~9g1 scoop protein powder~20-25g
GLP-1-friendly protein sources — meaning gentle on a slowed digestive system — include: Greek yogurt, eggs, soft-cooked fish, cottage cheese, tofu, edamame, and lentil soups. These digest more comfortably than large cuts of red meat when gastric emptying is already delayed.
2. Fiber — build to 30g per day
Fiber does three things that matter enormously on a GLP-1: it supports the gut microbiome (which is affected by dietary changes), slows the absorption of glucose (supporting the blood sugar work the medication is already doing), and keeps digestion moving on a stomach that's working more slowly than usual.
The goal is 30g of fiber per day, introduced gradually. A sudden jump from low fiber to high fiber can worsen the bloating and nausea that are already common GLP-1 side effects. Start lower and build up over two to three weeks.
Your best fiber sources:
Cooked vegetables over raw (easier to digest) — spinach, broccoli, green beans, carrots
Legumes — lentils, chickpeas, black beans
Oats and quinoa
Berries — particularly raspberries and blackberries
Chia seeds (in smoothies or yogurt)
Sweet potato (with skin)
One practical note: raw cruciferous vegetables (raw broccoli, raw cauliflower, raw cabbage) can worsen bloating when digestion is already slow. Cook them instead.
3. Hydration — at least 2–2.5 liters of water daily
This one is consistently underestimated. Reduced appetite doesn't just mean eating less — it means drinking less, too. Dehydration accelerates fatigue, worsens nausea, and can amplify constipation, one of the most common GLP-1 side effects.
The general target is 2 to 2.5 liters of water per day — and if you're experiencing GI side effects, electrolytes (particularly sodium, potassium, and magnesium) matter as well.
Practical tips:
Carry a water bottle and link drinking to existing habits (after every small meal, before and after movement)
Broth and soups count toward fluid intake and provide electrolytes — particularly useful on days when nausea is high
Avoid drinking large amounts of liquid during meals, as this can worsen the sensation of fullness and bloating
Herbal teas (ginger tea especially, for nausea) are a useful warm-fluid option
A Full Day of Eating on a GLP-1
Target: ~100g protein, ~30g fiber, adequate hydration. Smaller portions than typical — designed to be nutrient-dense, not volume-dependent.
Morning | Breakfast
Greek yogurt protein bowl
¾ cup plain full-fat Greek yogurt
½ cup mixed berries (fresh or frozen)
1 tbsp chia seeds
Small handful of walnuts
Drizzle of raw honey (optional)
~19g protein | ~7g fiber
Start the day with a large glass of water — before coffee.
Mid-Morning | Optional Light Snack
2 soft-boiled eggs
A few slices of cucumber or a handful of cherry tomatoes
~12g protein | ~1g fiber
Midday | Lunch
Mediterranean lentil bowl
½ cup cooked green or French lentils
2 oz grilled or canned salmon (or roasted chickpeas for plant-based)
Roasted vegetables (zucchini, red pepper, spinach)
Drizzle of olive oil and lemon
Fresh herbs (parsley or mint)
~28g protein | ~10g fiber
Warm food is generally easier to digest than cold — especially on days when nausea is present.
Afternoon | Snack
½ cup cottage cheese
A few slices of cucumber or a small pear
Optional: sprinkle of pumpkin seeds
~14g protein | ~3g fiber
Evening | Dinner
Herb-baked fish with roasted vegetables and quinoa
4 oz white fish (cod, halibut) or salmon, baked or pan-seared
½ cup cooked quinoa
Generous portion of roasted courgette, asparagus, and cherry tomatoes
Olive oil and garlic
~28g protein | ~8g fiber
Keep dinner portions moderate. GLP-1 medications significantly slow gastric emptying — a large evening meal is one of the most common triggers for nighttime nausea and reflux.
Day Total: ~101g protein | ~29g fiber
What to Limit (and Why)
A few categories consistently worsen GLP-1 side effects — not because they're inherently bad foods, but because of how they interact with a stomach that's already working more slowly:
High-fat fried foods — Slow digestion further, significantly increase nausea and reflux risk.
Large portions of red meat in one sitting — Heavy on the gut when gastric emptying is delayed. Not off the menu entirely — just smaller amounts, more often.
Sugary beverages and ultra-processed snacks — These provide quick glucose hits that work against the blood sugar regulation the medication is supporting.
Carbonated drinks during meals — Can dramatically worsen bloating and distension.
Alcohol — Interestingly, research published in JAMA Psychiatry suggests semaglutide may naturally reduce alcohol cravings. On a practical level, alcohol on a near-empty stomach hits harder and depletes key nutrients your body especially needs on a reduced-calorie intake.
The Bigger Picture
The most important mindset shift I work on with clients on GLP-1 medications is this: the medication has quieted the noise. Your job now is to make the most of the quiet.
Appetite suppression is a tool. It creates the conditions to nourish your body more intentionally than before — not an excuse to under-eat, under-protein, and drift through the day on coffee and a few crackers.
Research from Mass General Brigham, published in 2025, put it plainly: combining GLP-1 therapy with both adequate protein intake and resistance training produces significantly better body composition outcomes than medication alone. The medication is doing real work. You deserve to do real work alongside it.
If you're on a GLP-1 and navigating what to eat — start here. Protein at every meal, fiber built up gradually, water as a non-negotiable. The rest gets more nuanced from there, and I'm here for those conversations.
References:
Wilding, J.P.H. et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. https://doi.org/10.1056/NEJMoa2032183
Haines, M. et al. (2025). Protein intake and lean mass preservation on semaglutide. Presented at ENDO 2025. Endocrine Society. https://www.endocrine.org/news-and-advocacy/news-room/endo-annual-meeting/endo-2025-press-releases/haines-press-release
Peralta-Re, D. et al. (2025). Resistance training and protein intake in GLP-1 users. Medscape / Obesity Medicine, April 2025. https://www.medscape.com/viewarticle/resistance-training-protein-may-lower-glp-1-ra-muscle-loss-2025a10008x6
Mass General Brigham. (2025). Preserving Lean Body Mass in Patients Taking GLP-1 for Weight Loss. Advances in Motion. https://advances.massgeneral.org/endocrinology/article.aspx?id=1601
ACE Fitness. (2025). GLP-1s and Lean Mass: What the Research Shows. ACE Certified, June 2025. https://www.acefitness.org/continuing-education/certified/june-2025/8892/glp-1s-and-lean-mass-what-the-research-shows/
