Important Note
This article provides general nutritional guidance. If you're taking GLP-1 medications, work with your prescribing doctor or a registered dietitian for personalised advice. These medications are powerful tools that work best with proper dietary support.
GLP-1 receptor agonists - including semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) - have transformed weight management by dramatically reducing appetite. But reduced appetite creates a challenge: when you eat significantly less, every calorie needs to count nutritionally.
The goal isn't just weight loss. It's losing weight while preserving muscle mass, maintaining energy, and avoiding nutritional deficiencies. This requires strategic eating.
How GLP-1 Drugs Affect Eating
Understanding what these medications do helps explain why diet matters so much:
- Reduced appetite - You feel full faster and stay full longer
- Slower gastric emptying - Food stays in your stomach longer
- Changed food preferences - Many people lose interest in greasy or sweet foods
- Nausea with certain foods - High-fat and large meals often trigger discomfort
- Calorie intake drops significantly - Often by 30-40%
With dramatically reduced food intake, there's less room for empty calories. Every meal needs to deliver nutrition.
The Priority: Protein
Why Protein Is Non-Negotiable
Rapid weight loss risks losing muscle along with fat. Adequate protein helps preserve lean mass, which is crucial for metabolic health, strength, and long-term weight maintenance. Aim for 1.0-1.2g of protein per kg of body weight daily - that's 70-85g for a 70kg person. Since you're eating less overall, protein should be the priority at every meal.
Good protein sources:
- Chicken, turkey, lean beef
- Fish and seafood
- Eggs
- Greek yoghurt
- Cottage cheese
- Legumes (beans, lentils)
- Tofu and tempeh
What to Eat (and Avoid)
Foods That Work Well
- Lean proteins (chicken, fish, eggs)
- Non-starchy vegetables
- Whole grains in moderate portions
- Fruit (especially berries)
- Low-fat dairy
- Legumes
- Healthy fats in small amounts
- Clear soups and broths
Foods to Limit or Avoid
- High-fat foods (often cause nausea)
- Fried foods
- Sugary foods and drinks
- Large portions of any food
- Alcohol (increased sensitivity)
- Carbonated drinks
- Very spicy foods
- Processed/ultra-processed foods
Practical Eating Strategies
Daily Eating Tips
- Eat protein first - Start every meal with protein before moving to vegetables, then carbs
- Small, frequent meals - 4-5 smaller meals may work better than 3 larger ones
- Eat slowly - Take 20-30 minutes per meal; your stomach needs time to register fullness
- Stop when satisfied - Not stuffed. Overeating on GLP-1s causes significant discomfort
- Stay hydrated - Drink water between meals, not during, to avoid early fullness
- Plan meals - With reduced appetite, it's easy to skip meals and miss nutrition
Managing Side Effects Through Diet
Common GLP-1 side effects can be minimised with dietary adjustments:
Nausea
- Eat bland foods when symptoms are worst
- Avoid lying down immediately after eating
- Ginger tea may help
- Small portions reduce nausea triggers
Constipation
- Prioritise fibre from vegetables and whole grains
- Stay well hydrated (minimum 2 litres daily)
- Include prunes or kiwi fruit
- Gentle movement helps
Fatigue
- Often from insufficient calories - ensure you're eating enough
- Spread protein throughout the day
- Include complex carbohydrates for energy
- Check iron intake
Watch for Deficiencies
Eating significantly less increases risk of nutritional deficiencies. Common concerns include B12, iron, calcium, and vitamin D. Your doctor may recommend blood tests and supplements. Don't skip these - deficiencies can cause serious problems and may not be obvious until advanced.
Exercise and Muscle Preservation
Diet alone isn't enough to preserve muscle during rapid weight loss. Resistance training is strongly recommended:
- 2-3 strength training sessions per week
- All major muscle groups
- Progressive overload (gradually increasing weight)
- Protein after workouts supports muscle synthesis
Studies show that combining GLP-1 medications with resistance training results in better body composition - more fat lost, more muscle preserved - than medication alone.
Long-Term Considerations
These medications often work long-term, which means your eating habits need to be sustainable:
- Build habits, not restrictions - Focus on what to eat, not just what to avoid
- Learn to enjoy smaller portions - Quality over quantity becomes the norm
- Monitor your health markers - Regular blood tests for deficiencies
- Plan for maintenance - Whether you stay on medication or taper, habits matter
The Bottom Line
GLP-1 medications reduce appetite dramatically, making nutrition per calorie more important than ever. Prioritise protein at every meal (aim for 1.0-1.2g per kg body weight) to preserve muscle mass. Eat small, frequent meals; choose whole foods over processed; avoid high-fat and sugary foods that often cause discomfort. Stay hydrated between meals, not during. Add resistance training to preserve muscle. Monitor for nutritional deficiencies with regular blood tests. The medication provides appetite control; you provide the nutritional quality. Together, they can support healthy, sustainable weight loss.
References
- Wilding, J.P.H., et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 384(11), 989-1002. doi:10.1056/NEJMoa2032183
- Jastreboff, A.M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 387(3), 205-216. doi:10.1056/NEJMoa2206038
- Sargeant, J.A., et al. (2019). A Review of the Effects of Glucagon-Like Peptide-1 Receptor Agonists and Sodium-Glucose Cotransporter 2 Inhibitors on Lean Body Mass in Humans. Endocrinology and Metabolism, 34(3), 247-262. doi:10.3803/EnM.2019.34.3.247
- Obesity Medicine Association. (2023). Nutrition considerations for GLP-1 receptor agonist therapy. obesitymedicine.org
