How to Work Out Your Calorie Deficit (Without Starving Yourself)

A deficit you cannot hold for twelve weeks is not a deficit. It is a diet you will quit.

Most people fail at fat loss not because they picked the wrong number, but because they picked an aggressive one, held it for nine days, and then ate their way back through it. The arithmetic below is deliberately unambitious. That is the point.

Step 1: estimate your maintenance calories

Maintenance is what you burn on an average day. There are precise laboratory methods and there is the version that works well enough:

Bodyweight in kg × 30 for a moderately active person. Mostly desk-bound with a couple of training sessions? Use 28. On your feet all day plus training? Use 33.

An 80 kg person who trains three times a week and sits at a desk lands around 2,240 calories.

This is an estimate, not a measurement. Its job is to give you a starting point, not a truth.

Step 2: subtract, but modestly

Take 15 to 20 percent off maintenance. For our 80 kg example that is roughly 1,800 to 1,900 calories.

That produces around 0.5 kg of fat loss per week. It sounds slow. It is also the rate at which most people keep their muscle, keep training hard and keep their sanity.

Larger deficits do work faster on paper. In practice they cost you strength in the gym, sleep quality and adherence, and the weight tends to come back with company.

Step 3: protect the muscle

In a deficit your body will take material from wherever it can. Two things decide whether that is fat or muscle:

• Protein. 1.6 to 2.2 g per kilogram of bodyweight. This matters more in a deficit than in a surplus. The practical breakdown is here.
• Resistance training. Keep lifting, and keep trying to progress. The signal that says "this muscle is needed" is load, not cardio.

Cut either one and you lose weight that includes muscle. The scale is happy, the mirror is not. The same applies to carbs if you cut them too hard while still training hard — low glycogen means less training volume, which means less muscle kept.

Beginner, returning after a break, or carrying some extra fat? With a small deficit like this you may even build muscle while losing fat — body recomposition explained.

Step 4: adjust from reality, not the calculator

This is the step almost everyone skips. Your estimate was a guess. After two weeks you have data:

• Weigh yourself in the same conditions, several mornings a week, and use the weekly average. Daily weight swings by a kilo or more from water and food volume alone — reacting to it is pointless.
• Lost roughly 0.4–0.7 kg per week? Your number is right. Do not change it.
• Nothing moved across two full weeks? Take another 100–150 calories off. Not 500.
• Dropping faster than 1 kg per week? Eat a bit more. That pace costs muscle.

Where the online calculators mislead you

They overestimate activity. "Moderately active" in most calculators assumes far more movement than three gym sessions. Pick the level below the one you think you are.

They ignore that the number moves. As you get lighter, maintenance falls. The deficit that worked in week one is a smaller deficit by week ten.

They imply precision that does not exist. A result of 2,247 calories is not more accurate than 2,250. It is the same guess with decimals.

The part nobody puts in the calculator

Adherence beats optimisation, every time. A 15 percent deficit you follow for four months does more than a 30 percent deficit you follow for eleven days.

Practical things that raise adherence more than any macro split:

• Eat protein at every meal — it is the most filling macronutrient by a wide margin
• Keep meals boring and repeatable on weekdays; decisions cost willpower
• Do not bank calories for the weekend. It rarely balances out
• Plan for the bad week rather than pretending it will not come

A high-protein breakfast in particular does a lot of work here — why eating more in the morning makes eating less all day easier.

Who should not do this

This is general nutrition education, not medical or dietary advice. If you are pregnant or breastfeeding, under 18, managing a medical condition, taking medication that affects appetite or blood sugar, or have any history of disordered eating, calorie targets are not the right tool for you and a qualified professional is. Please talk to one.

If you want it written out

The Calorie Deficit Handbook walks through the calculation with worked examples, the adjustment schedule and what to do when weight loss stalls.

Want the whole approach including food structure and habits, not just the number? The Complete Nutrition System. And for the practical side — actually hitting the protein target without cooking twice a day — the High-Protein Cookbook.

Common questions

Do I need to count calories forever?
No. Most people count for a few months, learn what portions look like, and then estimate. Counting is a teaching tool, not a lifestyle.

Do I have to hit my macros exactly?
Hit protein. Carbs and fat can move around it based on what you enjoy and what keeps you full.

Should I eat back the calories I burn training?
No. Fitness trackers overestimate training burn substantially, and your maintenance estimate already assumes you train.

Why has my weight not moved in five days?
Water. Fat loss does not show up on a linear graph. Judge by the weekly average across two weeks, nothing shorter.

General nutrition education, not medical advice.