Maintenance calorie calculator

How it’s calculated

By formula, three things add up, just like in the Evzia app:

1. Resting burn, with the Mifflin-St Jeor equation (1990), the most accurate of the common ones in adults (Frankenfield et al., 2005).
2. The rest of your day, not counting walking: resting burn × 1.2 (standing, housework, digesting food). The 1.2 is an assumption for a normal day, not a measurement.
3. Walking: your steps times the length of a step (0.414 × your height) give the kilometers, and each kilometer costs 0.5 kcal per kilo of body weight, the extra you burn walking on flat ground according to the ACSM.
4. Exercise, in net kcal: only what you burn on top, because the resting burn of those minutes is already counted.

Resting burn = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women
Maintenance = resting burn × 1.2 + walking + exercise

With your real data

If you eat a certain number of calories on average and your weight doesn’t move, those are your maintenance calories. If it does move, your body supplied or took away the difference:

Real maintenance = calories eaten − (final weight − starting weight) × kcal per kilo ÷ days

Kcal per kilo aren’t the same for everyone: when you lose or gain weight, it isn’t only fat that changes, but also muscle and water, which have far fewer. The calculator estimates them in three steps, like the app:

• your body fat % from your BMI, your age and your sex (Deurenberg et al., 1991);
• how much of the change is fat: more the more fat you have (Forbes, 2000);
• and the calories in each part: 9,440 kcal per kilo of fat and 1,816 per kilo of everything else (Hall, 2008).

The margin comes from the scale: half a kilo of water difference between the two weigh-ins, spread over the days. And the result is only as good as what you logged: what gets forgotten (oil, snacking) makes it come out lower than it really is.

A worked example

To get it right

• Weigh yourself in the morning, on an empty stomach and after using the bathroom, and use the average of 3 days at the start and at the end: water and food still in your body move your weight from one day to the next.
• Log everything you eat and drink on those days, including oil, sauces and snacking: what gets forgotten makes your maintenance come out lower than it really is.
• The more days, the better: in the example, half a kilo of water on the scale moves the result by about 250 kcal per day with 14 days, and about 120 with 28.
• If you’ve just started eating less (or more), let the first week pass: your weight drops or rises suddenly because of water and glycogen, not fat.
• For steps, use the average of a normal week. And don’t count as exercise what steps already count: walking or running outdoors.
• For the calories that suit your goal, continue with the calorie goal calculator.

Frequently asked questions

What are maintenance calories?

The calories you burn on a normal day, counting everything: what your body burns at rest, your everyday life, your walking and your exercise. If you eat that on average, your weight stays put, give or take the day-to-day swings of water. Eating less is a deficit; eating more is a surplus (what people at the gym call “bulking”).

Why don’t the formula and my real maintenance match?

The formula gives what people of your weight, height, age and sex burn on average, and your body may burn a bit more or less. Mifflin-St Jeor is the most accurate of the common resting equations, and it still misses by more than 10% for part of the population (Frankenfield et al., 2005). Real maintenance is measured on you: if you’ve logged what you eat well, that’s the one to trust.

Isn’t a kilo of weight 7,700 kcal?

That figure assumes everything you lose or gain is body fat. But muscle and water change too, and they have far fewer calories, and in what proportion depends on how much fat you have (Forbes, 2000; Hall, 2008). That’s why the calculator uses the kcal per kilo of your own body: for example, about 5,840 for a 30-year-old man who is 180 cm and 70 kg, and about 7,970 for a 50-year-old woman who is 160 cm and 90 kg.

How many days do I need for real maintenance?

At least 14, and 28 or more is better: with few days, the water the scale picks up weighs a lot in the math. The Evzia app uses the last 4 weeks, only the days you logged well, and blends it with the formula according to how reliable each piece of data is.

Do I need to add exercise?

Yes, if you exercise on top of walking: enter its net kcal as a daily average (if you do 3 sessions of 300 kcal a week, about 130 a day). Walking and running outdoors are already counted with your steps: don’t count them twice.