GLP-1 Calorie & Protein Calculator
Protect muscle on Ozempic — calculate your optimal daily calories and protein target.
Why Calories Matter on GLP-1 Medications
GLP-1 medications dramatically reduce appetite, often leading patients to eat far fewer calories than their body needs. While a calorie deficit is necessary for weight loss, eating too little — especially protein — causes the body to break down muscle tissue for energy. This muscle loss slows metabolism and makes maintaining weight long-term much harder. Many GLP-1 users report eating only 800-1,000 calories due to suppressed appetite, accelerating short-term loss but causing fatigue, nutrient deficiencies, hair loss, and significant muscle wasting.
The 500 Calorie Deficit Protocol
The standard evidence-based recommendation for sustainable weight loss is a 500 calorie per day deficit, producing approximately 1 pound of fat loss per week (3,500 calories = 1 lb fat). In the STEP-1 trial, participants using semaglutide with a 500 calorie deficit and 150 minutes of weekly exercise lost 14.9% body weight — significantly more than medication alone. This calculator applies that 500 calorie deficit to your TDEE, with a floor of 1,200 calories for women or 1,500 for men to prevent dangerous under-eating.
Protecting Muscle Mass on Ozempic and Wegovy
Research indicates 25-40% of weight lost on GLP-1 medications may come from lean muscle mass without adequate protein intake — higher than the 15-25% typical with dietary restriction alone. The most effective countermeasures are resistance training 2-3 times per week and meeting your daily protein target. Prioritize protein-dense foods like chicken, eggs, Greek yogurt, cottage cheese, and protein shakes, especially on days when appetite is most suppressed.
How Much Protein Do You Need on GLP-1?
Most nutrition researchers recommend 1.2-1.6g protein per kg body weight when in a calorie deficit wanting to preserve muscle. This calculator uses 1.2g/kg as a conservative minimum. For a 200-lb (91 kg) person that is 109-145g protein per day. Aim for the higher end if strength training or losing weight rapidly. Track protein using an app like Cronometer or MyFitnessPal — hitting your protein target is more important than obsessing over the exact fat-to-carb split.
Signs You Are Not Eating Enough on GLP-1
- Persistent fatigue and weakness not explained by other causes
- Hair thinning or shedding (telogen effluvium from caloric restriction)
- Feeling cold more often than usual
- Difficulty concentrating or brain fog
- Loss of strength despite regular activity
- Dizziness or lightheadedness from electrolyte imbalances
Frequently Asked Questions
What is Mifflin-St Jeor and why is it used?
Mifflin-St Jeor is the most validated BMR formula for adults, consistently outperforming older Harris-Benedict equations in accuracy studies. It is the standard formula used by dietitians and nutrition calculators worldwide.
Should I eat back exercise calories?
The activity multiplier already accounts for your typical exercise level. Only eat back calories from unusually intense sessions beyond your normal routine.
Can I eat under 1,200 calories if my appetite is that suppressed?
We strongly recommend against going below 1,200 cal (women) or 1,500 cal (men) without direct medical supervision. These levels make it nearly impossible to meet protein and micronutrient requirements, leading to muscle and bone loss.
Do I need to track macros or just calories?
Tracking protein is the most important habit. If you hit your protein target and stay within your calorie range, the exact fat-to-carb split matters less for most people.
Should I eat differently on injection days?
Some patients experience nausea shortly after injection. Lighter foods (soups, smoothies, soft proteins) may be easier on injection days. There is no clinical reason to eat differently, but adapting to personal tolerance is sensible.