Every successful fat-loss diet — keto, fasting, low-fat, point systems — works through one mechanism: it makes you eat fewer calories than you burn. That gap is the calorie deficit. The diets differ only in how they create it. Once you understand that, you can stop searching for the magic diet and start engineering a deficit you can actually sustain. Here's how.
Step 1: Find Your Maintenance Calories
Your deficit is measured against your Total Daily Energy Expenditure (TDEE) — what you burn on a normal day including activity. Estimate it with our calorie calculator, which uses the Mifflin-St Jeor equation. Be honest about your activity level: most desk workers who train three times a week are "moderately active" at best, and overstating activity is the number-one reason calculated deficits don't work.
Step 2: Choose the Size of Your Deficit
Bigger is not better. The deficit size determines not just how fast you lose, but what you lose and whether you can keep going:
| Deficit | Weekly loss | Best for | Trade-offs |
|---|---|---|---|
| 10–15% below TDEE | ~0.2–0.35 kg | Lean people, last few kilos | Slow, but muscle-sparing and easy to sustain |
| 20–25% below TDEE | ~0.4–0.6 kg | Most people, most of the time | The sweet spot of speed vs sustainability |
| 30%+ below TDEE | 0.7+ kg | Higher starting body fat, short pushes | Hunger, fatigue, muscle loss risk, rebound risk |
A useful rule of thumb: aim to lose 0.5–1% of your body weight per week. Heavier bodies can support faster absolute loss; lean bodies can't.
Step 3: Protect Muscle While You Cut
The goal is fat loss, not weight loss. Two levers keep the loss coming from fat:
- Protein: 2.0–2.4 g per kg of body weight while dieting. Use our protein calculator for your exact number. High protein also blunts hunger — the main thing that kills diets.
- Resistance training: 2–4 sessions per week signals your body to keep muscle. Cardio helps the deficit but doesn't send that signal.
Step 4: Track the Right Way
Daily scale weight is noisy — water, sodium, carbs and digestion swing it by a kilogram or more. Weigh daily under the same conditions (morning, after the bathroom, before food) but judge only the weekly average. Compare this week's average to last week's. Two flat weeks in a row means something needs adjusting; one flat week means nothing.
When the Scale Stalls
Plateaus are usually one of four things, in this order of likelihood:
- Tracking drift. Oils, sauces, bites while cooking, weekend untracked meals. An honest audit usually finds 200–400 hidden kcal/day.
- Water masking fat loss. New training, more sodium, poor sleep and stress all hold water for days to weeks. Fat is still leaving; the scale just can't see past the water.
- TDEE has dropped. You're lighter, and you subconsciously move less in a deficit. A 5 kg loss lowers TDEE by roughly 100–200 kcal/day.
- You're at the new maintenance. After a long diet, your intake may simply equal your reduced TDEE.
The fix for 3 and 4 is the same: drop intake by 100–200 kcal, or add 2,000–3,000 daily steps, and reassess after two more weeks.
Diet Breaks and the Long Game
For diets longer than 12 weeks, planned 1–2 week breaks at maintenance calories improve adherence, restore training quality, and give you a psychological reset. They are not "falling off the wagon" — they're part of the wagon. When you finish your cut, raise calories slowly (100–150 kcal/week) back toward your new maintenance instead of celebrating into an immediate rebound.
The Bottom Line
Calculate TDEE honestly, take 20% off it, eat plenty of protein, lift, and judge progress by weekly averages. Adjust in small steps only when two consecutive weeks demand it. It's not glamorous — it's just what works, repeatably, for almost everyone.