How to Work Out Your Calorie Deficit
Finding your calorie deficit involves two numbers: how many calories your body uses each day (your total daily energy expenditure, or TDEE) and how many you are actually eating. The gap between those two figures is your deficit.
Step 1 — Estimate your daily calorie burn
Your TDEE is made up of your basal metabolic rate (the calories your body needs at rest) plus the energy used through movement and daily activity. Online TDEE calculators use your weight, height, age, and activity level to give a general estimate. These figures are estimates, not precise measurements — individual metabolism varies, and the number shifts as your weight changes.
Step 2 — Track how many calories you are eating
Log everything you eat and drink over a typical day. Many people find this the harder part, especially when appetite is unpredictable on a GLP-1 medicine. A general educational guide used in many contexts is that a deficit of around 500 calories a day is broadly associated with gradual, steady loss — but the right figure for you is something to discuss with your prescriber or a registered dietitian, who can take your full picture into account.
Step 3 — Make sure protein is not being squeezed out
When appetite drops sharply, overall calories fall quickly — but adequate protein is important for preserving muscle while losing fat. Prioritising protein-rich foods within a calorie-reduced intake is something many people on GLP-1 medicines find valuable. For more on this, see our guide to understanding your calorie deficit and the practical detail on what your calorie deficit should be.
Why this matters on a GLP-1 medicine
GLP-1 medicines reduce appetite, but they do not make every food choice automatic. Knowing your rough calorie range helps you stay consistent, avoid under-eating to a degree that affects energy and muscle, and have a more informed conversation at your next prescriber check-in. The broader context on managing a calorie deficit on a GLP-1 journey covers all of this in one place.
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Tracking the right four numbers — weight, waist, protein and dose — turns a noisy chart into a clear story. That's the loop GLP-1 users keep coming back for.
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Track Your Calorie Deficit Automatically with GLP Trackr
Working out your calorie deficit by hand every day is time-consuming — GLP Trackr makes it effortless. The app's AI photo food scan is the fastest way to log what you have eaten: point your camera at a meal and the app returns an instant calorie and protein breakdown, no manual searching needed. When appetite is low and meals are small, that speed matters.
Once your food is logged, GLP Trackr maps it against your calorie and protein targets so you can see your running deficit across the day at a glance. The daily check-in also captures weight, energy, and food-noise levels, so over time you can spot how your deficit and your sense of fullness are actually moving together — insight that is genuinely useful to bring to a prescriber appointment.
GLP Trackr is not a clinical tool and does not replace guidance from your prescriber or doctor — always discuss your calorie goals with a qualified healthcare professional who knows your individual situation. But for logging, pattern-spotting, and staying consistent day to day, it gives you a clear picture that is otherwise easy to lose track of.
Ready to see your calorie deficit in real time? GLP Trackr is free to try for 7 days — available now on the App Store and Google Play.
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Frequently asked questions.
A calorie deficit occurs when you consume fewer calories than your body uses in a day. The difference between your total daily energy expenditure and your calorie intake is your deficit. On a GLP-1 medicine, reduced appetite often creates a natural deficit, but tracking it helps you stay in a healthy range.
Estimate your total daily energy expenditure (TDEE) using an online calculator based on your weight, height, age, and activity level, then subtract the calories you eat each day. The result is your approximate deficit. These are estimates — your prescriber or a dietitian can help you set a personalised target.
A general educational reference is that a moderate daily deficit is broadly associated with gradual fat loss, but the right amount varies by individual. Your prescriber or a registered dietitian is best placed to advise on a target that suits your health, weight, and how you are responding to the medicine.
Yes. GLP Trackr lets you log food by AI photo scan, barcode, or search, and tracks calories and protein against your daily targets. You can see your running deficit at a glance and review patterns over time, which can be useful context for conversations with your prescriber.
When overall calorie intake drops, there is a risk of not eating enough protein to maintain muscle mass. Many people on GLP-1 medicines find prioritising protein-rich foods within a reduced-calorie intake helps them feel better and support body composition during their journey.