How many calories should you eat to lose weight?

“Just eat less” is the advice almost everyone lands on eventually, and it isn’t wrong, exactly. Weight loss does come down to energy: taking in a little less than your body burns, consistently, over time. But a little less than what? is the question that actually matters, and it’s the one most people skip straight past. Guess too high and the scale refuses to budge. Guess too low and you’re so hungry and flat that you’ve given up by Wednesday.

This is a practical guide to finding a calorie target that’s low enough to work and high enough to actually live with. It also covers why the number, on its own, is only ever half the story.

The simple maths behind a deficit

Your body needs a certain amount of energy every day just to keep you alive and moving. Take in less than that and it makes up the difference by drawing on stored energy, body fat included. That gap between what you eat and what you burn is called a calorie deficit, and it’s the one thing every successful weight-loss approach has in common, whatever name it goes by.

In South Africa, food labels give you energy in kilojoules rather than calories, so it helps to know the conversion. Roughly, 1 calorie is about 4.2 kilojoules. A 2 000-calorie day is close to 8 400 kilojoules. Set your daily target in calories, read kilojoules off the packet, and either works so long as you’re consistent.

As a rough rule of thumb, a deficit of around 500 calories a day tends to produce a steady loss of roughly half a kilogram a week. That may sound modest. It is, and that’s exactly why it holds.

Finding your maintenance number first

Before you can subtract anything, you need to know your starting point: the calories that keep your weight steady. This is your total daily energy expenditure, and it’s built from two parts. The first is the energy your body uses at complete rest just to keep your heart beating and your organs running, which is the majority of what you burn. The second is everything on top: walking, working, training, fidgeting.

That number depends on your weight, height, age, sex and how active you are. A larger, younger, more active body burns more. A smaller, older, more sedentary one burns less. Rather than guess, put your own details in below and let it do the arithmetic.

Treat the result as a well-educated estimate, not a law of physics. The “activity” setting, in particular, is where most people flatter themselves. Start with the number, then adjust to what the scale actually does over two or three weeks.

How big should the gap be?

Bigger is not better here. A gentle deficit is easier to sustain and far less likely to trigger the ravenous rebound that ends most diets. It also protects your muscle and energy. A savage one might move the scale faster for a fortnight, but it tends to collapse under its own weight.

Some sensible guardrails:

• Aim for a deficit of roughly 15% to 25% below your maintenance number. For many people that lands somewhere around 400 to 600 calories a day.
• Don’t go too low. As a general safety floor, most women shouldn’t drop below about 1 200 calories a day and most men below about 1 500 without proper supervision. Below that it’s hard to get enough protein, fibre and micronutrients.
• Give it time. Weight moves in a jagged line, not a straight one. Water, hormones and what you ate yesterday all add noise. Judge progress over weeks, not days.

The best calorie target isn’t the lowest one you can survive. It’s the one you’ll still be following in three months without hating your life.

If you’re tempted to slash harder and “get it over with”, it’s worth reading why steady weight loss beats crash dieting every time. Faster almost always costs more than it gives back.

Why “eat less” is rarely the whole answer

Here’s where the pure numbers game breaks down. Calories tell you how much energy is in your food, but not what that food does once it’s inside you. Three hundred calories of eggs, biltong and beans keeps you full for hours. The same three hundred calories from a cold drink and a couple of biscuits is gone in minutes and leaves you hunting for more.

Two levers change how a deficit feels:

Protein and fibre

Both are powerfully filling for the calories they carry, and protein also helps protect the muscle you don’t want to lose. Building meals around a protein source and plenty of vegetables is the single most practical way to stay under your target without feeling deprived.

Your appetite hormones

Hunger isn’t just willpower, it’s chemistry. GLP-1, a hormone your own gut releases when you eat, is part of the system that tells your brain you’ve had enough. When that signalling is sluggish, a “correct” calorie target can still feel like a daily fight. That’s a big part of why some people find a deficit harder to hold than others, and it’s not a character flaw.

When the number stops working

Two things reliably trip people up. The first is honest measurement: oils, sauces, “just a taste” while cooking and generous portions add up fast, and most of us underestimate by more than we’d admit. The second is that your target moves. As you lose weight, a smaller body burns fewer calories, so the deficit that worked at the start slowly shrinks towards maintenance. That’s normal, so recalculate every few kilograms rather than assuming a plateau means something is broken.

And remember that the scale is only one signal. How your clothes fit, your energy through the day and the tape round your waist all matter too. If the number alone has you anxious, it can help to see where you sit on the bigger picture first. Our guide to understanding your BMI puts it in context.

Where support fits in

For some people, sensible eating and a modest deficit are enough. Plenty of others find that far easier said than done, especially when appetite is relentless or weight has crept up over years. That’s where a doctor-led approach can help: a proper assessment, a plan built around your numbers, and, where clinically appropriate, medically supervised options that work with your body’s own appetite signals rather than against them. You can see how it works if that sounds like you.

Start with the maths. Find your maintenance number, take a modest slice off the top, and build your meals around protein and vegetables so the deficit is one you can keep. Judge it by results over weeks. If it works, keep going. If it doesn’t, that’s useful information too, and a better reason to talk to a registered clinician than simply eating less and less.