How Many Calories Should You Eat to Lose Fat?

"How many calories should I eat to lose fat?" is the most common question we get — and almost every answer online is wrong for you specifically. The 1,500-calorie figure your friend used, the number a generic app spat out, the rule of thumb from a magazine: none of them know how much muscle you carry, how much you move, or how your body has adapted to past diets. And every one of those things changes the answer.

By the end of this article you'll understand three things most people never learn: why your maintenance number is the only figure that matters, how to size a deficit that burns fat instead of muscle, and why the calculator result is a starting line, not a finish line.

First, what a calorie actually is — and isn't

A calorie is simply a unit of energy. Fat loss obeys the law of energy balance: take in less energy than you expend over time, and your body makes up the difference by burning stored fuel. There is no food, supplement, or training trick that bypasses this. Anyone selling you fat loss "without counting calories" is either hiding the deficit inside their method or selling you fiction.

But — and this is the part the calorie-obsessed crowd gets wrong — the number is only half the story. A 600-calorie deficit made of protein and whole food produces a completely different body than a 600-calorie deficit made of biscuits, even though the scale moves the same. Calories decide whether you lose weight. What those calories are made of decides whether you lose fat or muscle. Hold both ideas at once and you understand more about nutrition than most people ever will.

Start with maintenance, not the deficit

Your maintenance calories are the amount that keeps your weight stable. Everything in fat loss is relative to this number — a deficit only means "below maintenance." So if you don't know your maintenance, you're not on a diet, you're guessing.

Most calculators estimate maintenance from your weight, height, age, and sex. That's fine as far as it goes, but it ignores the single biggest driver of your metabolism: lean body mass. Two people who both weigh 82 kg can have wildly different calorie needs if one carries 10 kg more muscle than the other. Muscle is metabolically expensive tissue — it costs energy to maintain around the clock — while fat is nearly inert. The more muscle you carry, the more you can eat and still lose.

The lean-mass advantage

This is why we use the Katch-McArdle equation, which calculates your resting metabolic rate from lean body mass rather than total weight:

• First we subtract your fat mass (bodyweight × body-fat %) to find your lean mass
• Then resting metabolic rate = 21.6 × lean mass + 370
• Maintenance = that resting figure × your activity multiplier

Because it accounts for muscle, it gives a far more accurate starting point — especially if you're lean, muscular, or have been training for a while. A generic weight-only formula will systematically underfeed a muscular person and overfeed a soft one. Katch-McArdle fixes that by asking the right question: not "how much do you weigh?" but "how much of you is metabolically active?"

How big should your deficit be?

Once you have maintenance, your fat-loss target is simply maintenance minus a daily deficit. The right size depends on how fast you want to go — and the smart way to express that is as a percentage of bodyweight per week, because a 110 kg person can safely lose far more per week than a 60 kg person:

• Gentle (0.5% per week) — most sustainable, best protects muscle, easiest to stick to. Ideal if you're already fairly lean.
• Steady (0.75% per week) — a solid middle ground for most people with moderate fat to lose.
• Aggressive (1% per week) — faster, but harder to maintain, hungrier, and riskier for muscle. Reserve it for higher starting body fat and short blocks.

For an 82 kg person, a steady pace works out to roughly a 600 kcal daily deficit and about 0.6 kg of fat loss per week. Bigger isn't better: crash deficits burn muscle, tank your training energy, spike hunger hormones, and rarely survive contact with a real week. The deficit you can repeat beats the deficit that looks impressive on a spreadsheet.

The mistake almost everyone makes: forgetting protein

A calorie deficit tells your body to use stored energy — but it does not decide whether that energy comes from fat or muscle. Protein and training make that call. In a deficit without enough protein, a meaningful share of what you lose is muscle, and every kilo of muscle you shed lowers your metabolism and makes the next phase harder.

Set protein from your lean mass — typically 2.0–2.8 g per kg of lean mass — and you flip the equation: your body holds onto muscle and pulls almost entirely from fat. This is the difference between ending a diet lean and strong versus simply ending up a smaller, softer version of where you started.

Why the scale lies (and what to watch instead)

Even at a perfect deficit, your weight will not fall in a straight line. Day to day, the scale is dominated by water — influenced by salt, carbs, sleep, stress, hormones, and even how recently you trained. It's entirely normal to see nothing for ten days and then drop a kilo overnight as your body releases retained water.

This is why judging your diet by a single weigh-in is a recipe for quitting. Track the multi-week trend instead: a weekly average, a tape measure around the waist, progress photos in the same light every fortnight. When the trend is flat for 2–3 weeks despite honest adherence, that's your signal to trim the deficit slightly — not before.

Put your numbers to work

Rather than guess, plug your stats into our free calorie & macro calculator. It uses the exact lean-mass method above to give you a maintenance figure, a fat-loss target, and a full macro breakdown in seconds — no sign-up. Change your weekly rate or diet style and watch the numbers update live.

The honest caveat

Any formula is a starting point, not a guarantee. Real bodies respond differently, metabolisms adapt, and life intervenes. The only way to find your true numbers is to set a sensible starting target, hold it consistently for two to three weeks, measure the trend, and adjust. That feedback loop — estimate, measure, adjust — is the entire game, and it's exactly what we run with coaching clients: weekly body-composition measurements that turn a formula's guess into a precise, moving target built from your real data.

If you want your numbers built from real data instead of a formula, book a free consultation.