fotorieThe short answer: fewer than you burn, but not too many fewer. The useful answer takes a bit more, because the number depends on you: your weight, your height, your age, how much you move, and how much reasonable haste you want to make. In this guide, we’ll teach you how to calculate it in two minutes and how to tell if the number you get makes sense.
If you prefer to skip the theory, the daily calorie calculator does the math for you. But it’s worth understanding where the number comes from.
First: how many calories you burn
It all starts with your expenditure. Your body burns energy even when you’re lying on the couch (that’s your basal metabolism) and burns more when you move, work, train, or simply digest food. The sum of all that is your total daily expenditure, and it’s the reference point for any plan.
The formula we use in consultation and at Fotorie is Mifflin-St Jeor, which works best for the general population:
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
That gives you your basal metabolism. Then it’s multiplied by an activity factor:
| Activity | Factor | Who fits |
|---|---|---|
| Sedentary | 1.2 | Desk job, little walking |
| Light | 1.375 | Walks daily or trains 1-3 days |
| Moderate | 1.55 | Trains 3-5 days a week |
| High | 1.725 | Trains 6-7 days or physical job |
An example. A 40-year-old woman, 72 kg and 165 cm, has a basal metabolism of 10 × 72 + 6.25 × 165 − 5 × 40 − 161 = 1,390 kcal. With light activity, her daily expenditure is around 1,910 kcal. That’s the figure at which she would maintain her weight.
Second: the reasonable deficit
To lose fat, you need to eat below your expenditure. The question is how much. In consultation, we almost always work with a deficit of between 300 and 500 kcal per day, which translates to about 0.25-0.5 kg per week. It’s a pace that can be sustained for months, respects muscle mass, and doesn’t trigger hunger.
Continuing with the example: 1,910 − 450 = about 1,450 kcal per day. With that, the woman in the example would lose about half a kilo per week, with better and worse weeks.
You can fine-tune the pace with the calorie deficit calculator, which tells you how many weeks it would take to reach your target weight with each deficit level.
The floors you shouldn’t cross
Here’s the important part. Lowering calories further doesn’t speed things up proportionally; beyond a certain point, everything gets worse. Below about 1,200 kcal for women and 1,500 for men, it’s difficult to meet protein, iron, calcium, and fiber needs, hunger becomes unbearable, and most people end up giving up after three weeks.
That’s why Fotorie doesn’t let the plan cross those floors, even if you choose the fastest pace. It’s the same criterion applied by the nutritionists at Vitasane in consultation: a plan you can stick to is worth more than a perfect one on paper.
These figures are guidelines for healthy adults. During pregnancy, lactation, for those under 18, with metabolic diseases, or on medication that affects appetite or weight, the number must be set by a professional.
How many calories according to your case
To give you an idea without calculating anything, this table shows the approximate calories to lose about 0.5 kg per week with light activity:
| Profile | Maintenance | For weight loss |
|---|---|---|
| Woman 30 years, 65 kg, 165 cm | 1,930 kcal | 1,450 kcal |
| Woman 50 years, 80 kg, 160 cm | 1,950 kcal | 1,450 kcal |
| Man 30 years, 85 kg, 178 cm | 2,550 kcal | 2,050 kcal |
| Man 50 years, 95 kg, 175 cm | 2,500 kcal | 2,000 kcal |
Notice that two people with very different weights can end up with similar figures, because age and height also matter. That’s why “1,200-calorie diets for everyone” fail so often: for a small, sedentary woman, they might be adequate, but for a tall man who trains, they are absurd.
Calories are not everything
With the number in hand, there are three things that make the difference between losing weight well and losing weight poorly:
- Sufficient protein. Between 1.6 and 2 g per kilo of body weight per day protects muscle while you lose fat and curbs hunger more than any other nutrient. For the woman in the example, about 115-145 g per day.
- Filling food. Vegetables, legumes, whole fruit, potatoes, oats. Same calories, much more volume. A plate of lentils and a chocolate bar can have the same kcal and are nothing alike.
- A pace you can maintain. The best deficit is the one you can sustain for three months, not the one that makes you lose two kilos in the first week (mostly water) and give up in the third.
How to know if you’re doing well
Daily weight is misleading: it goes up with salt, with your period, with a tough workout, with poor sleep. What matters is the trend over several weeks. If weighing yourself every morning, your weekly average drops between 0.25 and 0.5 kg, you’re doing well. If it’s been flat for three weeks, it’s time to review: either your expenditure was less than you thought (happens a lot with activity, people overestimate themselves) or you’re eating more than you’re tracking (happens even more).
That’s where an app really helps. Fotorie calculates your plan with this same formula, counts the calories of each dish from a photo, and shows you the weight trend instead of the daily number. If the trend doesn’t move, the coach tells you and suggests what to adjust.
In summary
- Calculate your expenditure with the Mifflin-St Jeor formula and your actual activity level.
- Subtract between 300 and 500 kcal. No more.
- Never go below 1,200 kcal (women) or 1,500 (men) without supervision.
- Prioritize protein and filling foods.
- Judge by the trend over several weeks, not by today’s weight.
And if you don’t want to do calculations every day, there’s a simpler way: take a photo of your plate and let the app do them for you.
