How many calories do you burn each day without doing anything?

Just by sitting here reading this article, your body is already burning energy. Your basal metabolic rate alone accounts for 60 to 70 % of your daily energy expenditure as a sedentary adult. This is the factor that has the greatest impact on your calorie balance—far more than exercise. I’ll show you how to estimate it, and why underestimating it can undermine your weight-loss efforts.

How many calories do you really burn while sitting still?

The body never stops. Even when you're at rest, you use energy to breathe, circulate your blood, and maintain your body temperature. This energy expenditure is called your basal metabolic rate, and it varies mainly based on your sex, weight, and height.

Data from ANSES allow us to estimate this baseline for an average adult. Here are the results, calculated based on the median level of physical activity used by the agency:

In other words, even before you think about exercising or walking, your body has already used up more than half of its daily calorie allowance. That’s why a diet that’s too strict is so hard on the body: it first taps into that essential reserve.

What exactly is basal metabolism?

Your total energy expenditure is broken down into three parts. Your basal metabolic rate accounts for 60 to 70 %, food digestion accounts for about 10 %, and the rest comes from your activity, including exercise and daily tasks.

In practical terms, this foundation powers your heart, lungs, and brain, and supports cell regeneration. It’s not something you can control: you can’t turn it off or skip it on a day when you’re feeling lazy—unlike a workout.

• The heart and breathing—in constant motion.
• Regulation of body temperature.
• Cell renewal and basic digestion.

How do you calculate your basal metabolic rate?

The most commonly used formula in nutrition today is that of Mifflin-St. Jeor (1990). It replaces the old Harris-Benedict formula, which is considered less accurate for today's body types.

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

📏 La formule de Mifflin-St Jeor (1990) donne l estimation la plus fiable de ton métabolisme de base sans matériel médical.

A 35-year-old woman who is 1.65 m tall and weighs 65 kg has approximately 1,380 kcal. A 35-year-old man who is 1.78 m tall and weighs 80 kg has approximately 1,755 kcal. This figure is only an estimate: only indirect calorimetry in a laboratory can provide an exact measurement.

What factors affect your energy expenditure?

Two people of the same weight may have different basal metabolic rates. Several factors come into play, and you can't change them all in the same way.

• Muscle mass : Muscle consumes more energy at rest than fat, even when at rest.
• Age : Your metabolism gradually slows down, and this decline becomes more pronounced during menopause.
• Sex : For the same weight, men generally have more lean body mass, and therefore a higher energy expenditure.
• Sleep : A chronic deficiency disrupts the hormonal regulation of your energy expenditure.

Above all, remember this: the more muscle you retain while losing weight, the higher your resting metabolic rate will remain. That’s one of the reasons why I always advocate for a moderate calorie deficit rather than drastic calorie restriction.

Why does a severe calorie deficit slow down your metabolism?

This is the most common mistake made by people who are eager to lose weight: drastically cutting calories to lose weight faster. The body reacts by slowing down its energy expenditure, a process known as metabolic adaptation.

⚠️ Un déficit de plus de 1 000 kcal par jour sans suivi médical augmente le risque de perte de masse musculaire et de ralentissement métabolique, selon la HAS (2011).

The HAS recommends a moderate calorie deficit—between 300 and 500 kcal per day—for gradual weight loss of approximately 0.5 kg per week. Skipping meals or neglecting What to eat for dinner often makes the problem worse: hunger leads to overeating later on, and the body interprets the deprivation as a warning signal.

The classic trap: the less you eat, the fewer calories your body burns to compensate. As a result, your weight plateaus despite your best efforts, and frustration sets in.

How can you use this number to lose weight without making a mistake?

Once you've estimated your basal metabolic rate, add your energy expenditure from physical activity to get your total energy expenditure. It's this total—never your basal metabolic rate alone—that you should use to calculate your calorie deficit. I recommend keeping this number somewhere where you can see it: it's your guide, not your enemy.

✅ Recalcule ton métabolisme de base tous les 5 to 10 kg lost: It decreases with weight, so your calorie deficit should follow suit.

Some people structure their meals around intermittent fasting to better maintain their calorie deficit throughout the day, while others prefer a breakfast that keeps them full until noon to avoid snacking. Both approaches work, as long as your total daily intake matches your basal metabolic rate.

The PNNS recommends at least 30 minutes of brisk walking or an equivalent activity per day, five times a week. This regular activity does not, strictly speaking, increase your basal metabolic rate, but when combined with a intermittent fasting When done right, it increases your total energy expenditure and preserves your muscle mass during a calorie deficit.

FAQ on Calories Burned While Doing Nothing