How Much of a Calorie Deficit Do You Need to Lose Weight?

A calorie deficit simply means your body is burning more energy than you are consuming. When that happens consistently over time, stored body fat is used as fuel — which is how weight loss occurs. The size of the deficit influences how quickly weight changes, but bigger is not always better: too large a deficit can increase fatigue, reduce muscle mass, and make the approach unsustainable.

The 500-calorie guideline — and why it is a starting point, not a rule

The often-quoted 500 kcal/day deficit is a rough population average based on the fact that roughly 3,500 kcal equates to approximately 0.45 kg (1 lb) of body fat. In practice, individual results vary — metabolic adaptation, body composition, hormone levels, and activity all play a role. For most adults, a moderate deficit of 400–600 kcal/day is a reasonable general range to aim for, but what that looks like in practice depends entirely on your own total daily energy expenditure (TDEE).

How much deficit to lose 1 kg?

Losing 1 kg of body fat requires burning approximately 7,700 kcal more than you consume. At a deficit of 500 kcal/day, that works out to roughly two weeks per kilogram — though real-world results differ because weight loss also involves water, glycogen, and lean tissue changes. For a closer look at what the numbers mean for a single pound, the page on calorie deficit needed to lose one pound goes into more detail, and losing 1 lb with a calorie deficit covers related practical context.

GLP-1 medicines and calorie intake

Medicines like Mounjaro (tirzepatide) and Wegovy (semaglutide) act on appetite-regulating pathways, and many people report a significantly reduced sense of hunger — sometimes called reduced "food noise" — which can make eating at a deficit feel more natural than it did before. This does not remove the need to track, however: reduced appetite can occasionally mean eating too little protein or too few total calories, which may affect energy levels and muscle maintenance. Understanding what a calorie deficit actually means is a helpful foundation before deciding on a target.

Knowing your target deficit is one thing — accurately tracking whether you are hitting it each day is another. GLP Trackr's AI-powered food photo scan is the most practical place to start: point your camera at a meal and get an instant calorie and macronutrient breakdown without manually searching every ingredient. For packaged foods, the barcode scanner fills in the details in seconds.

Once your daily calorie target is set in the app, GLP Trackr shows you your running total against that goal throughout the day, so you can see at a glance whether you are in deficit, on track, or at risk of under-eating. Protein targets sit alongside calories — important on a GLP-1 journey where appetite suppression can make it easy to miss protein goals without realising it.

The insights features pull your food and weight data together over time, helping you spot patterns — for example, whether the days you hit your calorie target tend to align with the weeks your weight moves. This kind of personal data is also useful to bring to your next prescriber appointment. For a broader look at how deficit tracking fits into the full picture, the calorie deficit hub brings together all the related guides in one place.

Keep in mind that calorie targets are general educational starting points. Your prescriber or doctor is the right person to advise on specific goals for your health situation — GLP Trackr helps you record and understand your intake so those conversations are informed by real data, not guesswork.

Ready to see your deficit in real numbers? GLP Trackr is free to try for 7 days — download it on the App Store or Google Play and start logging today.