Everyone wants the secret. After 18 years of coaching, I can tell you the truth is simpler than the supplement ads suggest: to lose fat, you have to eat fewer calories than your body burns. That's a calorie deficit, and it's the one non-negotiable of fat loss. The good news is you don't have to guess your number — let's find it.
Key takeaways:
- Fat loss requires a calorie deficit — eating less than you burn. Nothing overrides this.
- Find your maintenance (TDEE), then eat 15–20% below it.
- Aim to lose 0.5–1% of bodyweight per week — faster burns muscle.
- Protect muscle with enough protein and lifting, not crash dieting.
- Get your numbers from the macro calculator and calorie deficit calculator.
How many calories should you eat to lose fat?
Eat 15–20% below your maintenance calories (TDEE) — for most people that's 300–600 calories less per day than they burn. That deficit drives steady fat loss of about 0.5–1% of bodyweight per week without crushing your energy, your training, or your muscle. The exact number depends on your age, sex, size, and activity, so you need your maintenance figure first.
That's the answer in one paragraph. The rest is the four steps to find your number and make it actually work over months, not days.
Step 1 — Find your maintenance calories
Your maintenance level (your TDEE, Total Daily Energy Expenditure) is how many calories you burn in a day. Eat that amount and your weight holds steady. It's driven by your age, sex, body size, and activity level.
You can estimate it in about ten seconds with the macro calculator or the calorie deficit calculator — both use the Mifflin-St Jeor equation, the same formula I use when building client plans. Treat the result as a well-educated starting point, not gospel.
Step 2 — Set a sensible deficit
Once you know maintenance, subtract 15–20%. For most people that lands somewhere between 300 and 600 calories below maintenance. Here's how the common approaches compare:
| Deficit size | Weekly fat loss | Reality | | --- | --- | --- | | Crash (35%+ below) | Fast then stalls | Burns muscle, tanks energy, rebounds | | Moderate (15–20%) | 0.5–1% bodyweight/wk | Sustainable — the sweet spot | | Tiny (under 10%) | Very slow | Easy to undo with one bad day |
Bigger isn't better. A crash diet burns muscle, kills your energy, and is impossible to sustain. Slow and steady wins.
The calorie deficit calculator shows you mild, moderate, and aggressive targets side by side — and caps you at a minimum-safe floor so you never under-eat dangerously.
Step 3 — Protect your muscle with protein
In a deficit, your body will happily burn muscle alongside fat unless you give it a reason not to. Two reasons: eat enough protein (around 1.6–2.2 g per kg of bodyweight, toward the top end when cutting) and keep lifting weights. Muscle is what makes you look lean rather than just "smaller," and it keeps your metabolism up while you diet.
Not sure how much protein that is for you? I broke it down fully in how much protein do you really need, or get your target instantly from the protein calculator.
Step 4 — Adjust with real-world data
A calculator gives you a starting point, not a law of physics. Track your weight as a weekly average (daily weight swings 1–2 kg from water and food — ignore the single days). If the average isn't moving after two to three weeks, drop another 100–150 calories or add some daily steps. Bodies adapt as you lose weight; your plan should adapt too. This weekly-adjustment loop is exactly what separates people who keep losing from people who stall and quit.
The part most people skip
Consistency beats perfection. The "perfect" diet you quit in three weeks loses to the decent diet you follow for six months. Most fat-loss failures aren't about the wrong calorie number — they're about a plan too strict to live with. Set a moderate deficit, hit your protein, lift, and let weekly data steer. For more on where exercise fits, see cardio vs weights for fat loss; for stubborn midsection fat, how to lose belly fat.
Frequently asked questions
How fast can I safely lose fat?
About 0.5–1% of your bodyweight per week. For a 90 kg person that's roughly 0.45–0.9 kg weekly. Faster usually means you're losing muscle and water alongside fat, and it rebounds hard. Slower is more sustainable and protects your results.
Do I need to count calories forever?
No. Counting is a useful tool to learn portion sizes and where your calories come from, but many people transition to habit-based eating once they understand it. Even a few weeks of tracking teaches you enough to estimate accurately for life.
Why did my weight loss stall?
Usually one of three things: your maintenance dropped as you lost weight (so your old deficit is now maintenance), "calorie creep" from untracked extras, or normal water fluctuations masking fat loss. Judge by 2–3 week averages, and if truly stalled, cut 100–150 calories or add activity.
Is a calorie deficit all that matters?
For fat loss specifically, the deficit is what makes the scale move — it's the non-negotiable. But protein, training, sleep, and food quality determine what you lose (fat vs muscle) and how you feel doing it. The deficit is necessary; the rest is what makes it work and stick.
If you want a plan built around your life — with weekly adjustments so you never stall out — that's exactly what coaching is for. Apply for coaching and tell me where you're starting from.
This article is general information, not medical advice. Check with your physician before starting a calorie-restricted diet, especially if you have any health conditions.