How to set a calorie deficit you can actually keep

January is when everyone cuts too hard. A crash diet works for about ten days, then hunger, low energy and a bad weekend undo it. The goal is not the biggest possible deficit. It's the biggest deficit you can keep for twelve weeks without hating your life.

Step 1: find your maintenance calories

Maintenance is the number of calories at which your weight stays flat. Online calculators give a starting estimate from your height, weight, age and activity, but they can be off by 300 kcal or more in either direction. Treat the estimate as a first guess and let your own data correct it.

• Eat normally and log everything for 14 days. Don't diet yet.
• Weigh yourself every morning, after the toilet and before food.
• Average each week. Compare week two with week one.
• If the average didn't move, your average intake is maintenance. If it went up or down, adjust: roughly 7,700 kcal equals one kilogram of body weight, so 0.5 kg gained in a week means you ate about 550 kcal a day above maintenance.

Step 2: pick a deficit you can live with

Subtract 300–500 kcal from maintenance. For most people that means losing around 0.5–1% of body weight per week, which is fast enough to see in the mirror within a month and slow enough to protect muscle, sleep and training. If you have a lot to lose, the upper end is fine. If you are already lean, stay near the lower end.

Bigger deficits look attractive on paper, but they increase hunger and fatigue, make you move less without noticing, and make it harder to keep strength in the gym. The extra speed is often lost to the weekend that follows.

Step 3: set protein first

Once calories are set, fix protein at 1.6–2.2 g per kg of body weight. Protein helps you keep muscle while eating less, it's the most filling macronutrient, and your body burns slightly more energy digesting it. For an 80 kg person that's roughly 130–175 g a day, or 30–45 g across four meals.

Carbs and fat fill the remaining calories. The split matters far less than the total. Most people do best with enough carbohydrate to train well and enough fat, about 0.6–1 g per kg, to keep meals satisfying.

Step 4: make meals do the work

• Build every meal around a protein source: chicken, fish, eggs, Greek yogurt, tofu, lentils.
• Add volume with vegetables and fruit. They're filling for very few calories.
• Measure oils, nut butters and sauces. They're where hidden calories live.
• Repeat breakfasts and lunches. Fewer decisions means fewer mistakes.

Step 5: adjust with data, not panic

Daily weight swings of 1–2 kg are normal and mostly water, salt and food in your gut. Look at the weekly average. If it hasn't moved for two to three weeks and you've been consistent, take off another 100–200 kcal or add 2,000 daily steps. If you're losing faster than 1% a week and feel flat, add 100–150 kcal back.

Signs your deficit is too aggressive

• Your strength drops for two weeks in a row.
• You're hungry most of the day and sleeping badly.
• You keep 'starting again on Monday'.
• Training motivation has disappeared.

Any of these means it's time to ease off. A slightly slower diet that you actually follow will always beat a perfect plan you abandon.