How to Work Out a Calorie Deficit on Your GLP-1 Journey

A calorie deficit is created in two steps: estimating how many calories your body needs to maintain its current weight (your Total Daily Energy Expenditure, or TDEE), then eating a meaningful but sustainable amount below that figure.

Step 1 — Estimate your maintenance calories

Your maintenance calories depend on your basal metabolic rate (the energy your body uses at rest) plus the calories you burn through daily activity. Several widely used formulas — such as the Mifflin-St Jeor equation — use your weight, height, age, and activity level to give an estimate. These are estimates rather than precise measurements, so treat the output as a useful starting point rather than a fixed rule.

Step 2 — Set a deficit you can sustain

A commonly cited general range is a deficit of around 500 calories per day, which many nutrition guidelines associate with gradual, steady loss. Larger deficits can feel manageable on a GLP-1 medicine when appetite is low, but eating too little can compromise protein intake, energy levels, and muscle mass — all of which matter for long-term results. Most general guidance suggests staying above around 1,200–1,500 calories per day as a rough lower floor, though the right level for any individual depends on factors only their prescriber or doctor can assess.

Why protein matters inside your deficit

When calories are reduced, getting enough protein helps preserve muscle and keeps you feeling fuller for longer. Many people on GLP-1 medicines find their overall food volume drops significantly, which makes every calorie count more — prioritising protein-dense foods is one of the most practical steps you can take. For a closer look at how to count the calories in what you eat, including reading labels and estimating portions, that guide covers the basics in detail.

For a fuller breakdown of the calculation itself, the calorie deficit calculator on GLP Trackr walks through each variable and gives you a personalised estimate to work from.

Knowing the theory is one thing — hitting your numbers day after day is where most people need practical support, and that is exactly where GLP Trackr is built to help.

The fastest way to stay inside your deficit is the AI photo scan: point your camera at a meal and GLP Trackr instantly estimates the calories, protein, and macros without any manual searching. On days when appetite is low and meals are small and irregular, the friction of typing everything in can quietly kill the habit — removing that friction makes consistent logging far more likely.

Once you have set a daily calorie and protein target inside the app, your food log feeds directly into your targets dashboard, so you can see at a glance how much room you have left in your deficit for the day. The weekly insights then surface patterns — whether you are consistently under-eating on certain days, or whether protein is slipping when calories drop — giving you something concrete to discuss with your prescriber or a dietitian.

You can read more about building a sustainable approach on the calorie deficit guide, which covers the full picture of managing nutrition on a GLP-1 medicine.

As always, the figures the app helps you track are a general tool for self-awareness, not a medical prescription. If you have questions about the right calorie level for your health situation, your prescriber or doctor is the right person to ask — they know your full history in a way no app can.

Ready to make your deficit work for you? Download GLP Trackr on the App Store or Google Play and explore it free for 7 days — snap your first meal, set your targets, and let the numbers take care of themselves.