- A calorie deficit means you take in a bit less energy than you use. Only then does your body draw on its reserves.
- A sensible deficit is mild: roughly 10 to 20% below your maintenance needs, which is about 300 to 500 kcal a day.
- A safe pace is around 0.25 to 1% of body weight per week. Going faster usually doesn't pay off.
- The method: calculate your BMR, multiply by activity (TDEE), subtract the deficit, and adjust after two weeks based on the trend.
Every diet that works, works for the same reason: it puts you in a calorie deficit. They differ only in how hard they are to stick with. Here's a simple way to calculate your deficit and set it sensibly without driving yourself crazy.
What is a calorie deficit
Your body uses a certain amount of energy every day to breathe, digest and move. If it gets less than it needs from food, it takes the missing energy from its reserves, and part of those reserves is body fat. We call this state a deficit. If you take in more than you use, that's a surplus and your weight goes up.
So there's nothing magical about a deficit. It's the difference between what you eat and what you burn. You'll find the basics in the guide How to count calories.
How to calculate your deficit
You need two numbers. The first is your BMR, the energy you use at rest. The second is your TDEE, your total daily expenditure including movement. You can estimate BMR with the Mifflin-St Jeor formula:
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Then multiply BMR by an activity factor:
| Activity level | Description | Factor |
|---|---|---|
| Sedentary | Office job, very little movement | × 1.2 |
| Lightly active | Light exercise 1 to 3 times a week | × 1.375 |
| Active | Exercise 3 to 5 times a week | × 1.55 |
| Very active | Intense exercise almost every day | × 1.725 |
A man, 35 years old, 180 cm, 90 kg, lightly active. BMR = 10 × 90 + 6.25 × 180 − 5 × 35 + 5 = 1,855 kcal. TDEE = 1,855 × 1.375 ≈ 2,550 kcal per day. A deficit of around 15% is about 380 kcal, so the target comes out at roughly 2,170 kcal per day.
For a quick result without doing the math, use the calculator on the home page. Remember that this is an estimate. Your real needs vary with genetics, muscle mass and everyday movement.
How big should the deficit be
The temptation is obvious: the more you cut, the faster it goes. In practice it works the other way around. A big deficit brings hunger, fatigue, a worse mood and a greater chance that you'll "break" after a few weeks.
| Deficit size | What it means | What to watch for |
|---|---|---|
| Mild (10 to 15%) | Slow but comfortable pace. | Takes patience, and results only show after weeks. |
| Moderate (15 to 20%) | A good compromise for most people. | Watch your hunger, sleep and energy. |
| Large (over 20%) | Faster loss, but harder. | Higher risk of losing muscle and regaining weight. Only briefly and with care. |
As a rough guide, 1 kg of body fat corresponds to about 7,700 kcal. A deficit of 400 kcal a day is therefore about 2,800 kcal a week, which works out to a little over a third of a kilogram. Take it as a rough estimate. Your weight also fluctuates with water and digestion, so you can never predict the result exactly.
Never drop to a very low intake. As a rough warning, don't go below about 1,200 kcal (women) or 1,500 kcal (men) without medical supervision. A deficit isn't suitable for pregnant or breastfeeding women, minors, or people who have or have had an eating disorder. If you have a medical condition or take medication, talk to your doctor.
How to set your deficit in five steps
- Calculate your TDEE. Use the formula above or the calculator.
- Subtract 300 to 500 kcal. Or 10 to 20% of your TDEE, whichever suits you.
- Split the calories across meals. For inspiration, check out these healthy lunches under 600 kcal.
- Track the average. Weigh yourself the same way each time, for example in the morning after using the toilet, and compare weekly averages, not individual days.
- Adjust after two to three weeks. If the scale isn't moving, eat a little less or move more. If it drops too fast, eat more.
How to create a deficit through movement too
You don't have to create your deficit through food alone. Part of it can come from movement: more steps, walking, home workouts or sport. The upside is that you can eat a bit more and don't feel so restricted. Caloora estimates the calories you burn from workouts and steps and factors them into your daily budget. It's only an estimate, so don't treat exercise as a "reward" you have to eat right back.
If you want to start without a gym, see home workouts with no equipment.
Pick a goal and the app calculates your daily calorie and macro budget and shows how much you have left. Free to start.
Try Caloora freeHow to stick with a deficit
- Protein at every meal. It keeps you full and helps you hold on to muscle.
- Lots of volume, few calories. Vegetables, legumes and soups fill the plate.
- Plan, don't forbid. Build your favorite foods into your budget and a "blowout" day won't tempt you.
- Water and sleep. Thirst is often mistaken for hunger. You'll find tips in the guide on how much water to drink.
- Diet break. If your deficit lasts for months, give yourself a week at maintenance level now and then.
You can check the values of everyday foods in the calorie database. For the whole plan, from deficit through movement to habits, see the guide How to lose weight in a healthy, sustainable way.
Frequently asked questions
How big a calorie deficit is safe?
For most adults a mild deficit is sensible, roughly 10 to 20% below maintenance or 300 to 500 kcal a day. A pace of around 0.25 to 1% of body weight per week is considered safe. If you have health problems, talk to your doctor.
Why am I not losing weight even though I'm in a deficit?
Most often it's underestimating intake: oils, drinks, sauces and weekends. Your weight also fluctuates with water and salt, so track the average over 7 to 14 days. If nothing changes even after three weeks, adjust your intake or movement slightly.
Can I eat less than 1,200 kcal?
We don't recommend it without medical supervision. A very low intake raises the risk of nutrient deficiencies, muscle loss and regaining weight afterward. It's better to choose a mild deficit and add movement.
Do I have to exercise to lose weight?
No, you can lose weight with a food deficit alone. Exercise does help you keep muscle, improves your mood and makes a deficit easier, though. Even regular walking is a good start.
How long can I stay in a calorie deficit?
A mild deficit can be held for several weeks or even months if you feel good. If fatigue, poor sleep or a plateau appear, give yourself a week at maintenance level. For longer plans, talk to a doctor or dietitian.
The information on this page is general and educational. It does not replace advice from a doctor, dietitian or trainer. If you have a health condition, take medication, or are pregnant or breastfeeding, talk to a professional before changing your diet or exercise.