How many calories should I eat to lose weight?

The short answer: it depends on your body. The 2000 calories printed on every label is not a recommendation for you — it is a statistical average. Here is how to work out your real number.

Why "2000 calories" is almost never your number

That figure exists so percentages can be printed on packaging. It takes no account of your weight, your height, your age or how much you move.

A 60-year-old woman of 58 kg with a desk job and a 30-year-old man of 95 kg who works on his feet cannot eat the same amount. If both follow "2000", one gains weight and the other is permanently hungry.

Step 1: your basal metabolic rate

This is what your body burns at complete rest, just to breathe, pump blood and stay warm. The formula most used in clinic is Mifflin-St Jeor:

• Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
• Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5

Example: a woman of 55, 72 kg, 160 cm → (10×72) + (6.25×160) − (5×55) − 161 = 1284 calories at rest.

Step 2: multiply by your activity

• Sedentary (desk job, little movement): × 1.2
• Light (some walking, 1-3 days of exercise): × 1.375
• Moderate (3-5 days of exercise): × 1.55
• Active (near-daily exercise or physical work): × 1.725

Continuing the example: 1284 × 1.2 = 1541 calories to maintain current weight.

Step 3: the deficit

To lose weight you subtract about 500 calories a day, which is roughly half a kilo per week.

1541 − 500 = 1041… but there is an important limit here.

The floor you should not cross

Below 1200 calories for women and 1500 for men, it becomes very hard to cover the vitamins and protein your body needs, and you lose muscle along with the fat.

In the example, the result is adjusted to 1200, not 1041. If the deficit then looks too small, the answer is not to eat less: it is to move more.

Why losing weight fast costs you

With an aggressive deficit you lose muscle as well as fat. Less muscle means a slower metabolism, which is why the weight comes back as soon as you eat normally again — often with interest.

Half a kilo to one kilo per week is the range that holds over time.

Calories are not the whole story

Fifteen hundred calories of soda and pastry and fifteen hundred of vegetables, protein and whole grains do different things in your body, even though the number is identical.

• Protein satisfies more and protects muscle while you lose weight.
• Fibre fills you up on fewer calories.
• Liquid sugar satisfies nothing: a juice is calories your brain never registers as food.

If you have another condition, this changes

With diabetes, how you spread carbohydrates across the day matters as much as the calories. With kidney disease, protein cannot simply be increased even though it satisfies more — there, your nephrologist sets the numbers. With high blood pressure, losing weight is often what lowers it most.

In all those cases the number above is a starting point for a conversation with your doctor, not a medical instruction.

Keep reading

• Type 2 diabetes diet: what to eat and what to avoid
• High blood pressure diet: where the sodium hides