Sunday. You are sprawled on the sofa, halfway through a movie, getting up only to fetch water.
You think you have barely used any energy today. But your body is still working hard. Your heart beats about a hundred thousand times. Your lungs breathe more than twenty thousand times. Your brain keeps thinking, your liver keeps filtering, and your body temperature stays around 37°C.
All of that costs energy. More than you might think. It goes by two abbreviations: BMR and TDEE.
In this article
BMR: your body's "standby" electricity bill
BMR (basal metabolic rate) is, simply put, the energy your body needs to stay alive when you are lying completely still.
Think of the fridge at home. Nobody opens the door, yet it keeps running and the electricity meter keeps turning. BMR is that "standby" part of the bill.
Who spends the most here? Small but hard-working organs:
- The brain is only about 2% of your body weight, but uses roughly a fifth of your resting energy.
- The liver, heart and kidneys are big "consumers" too.
- Muscle at rest uses less per gram, but because there is so much of it, it adds up.
For many people who do not move much, BMR makes up about 60 to 70% of the day's energy. In other words, most of the calories you eat go toward... being alive.
TDEE: the whole day's bill
TDEE (total daily energy expenditure) is the total energy you use in a day. It has three parts:
| Part | What it is | Share (approx.) |
|---|---|---|
| BMR | Energy to stay alive while lying still | 60 to 70% |
| Digesting food | Chewing, digesting, absorbing, storing | about 10% |
| Movement | Exercise and every movement of the day | The rest, and it varies the most |
The digestion part has its own name: the thermic effect of food. Fun fact: digesting protein takes more energy than digesting fat or carbs.
Movement is not just your gym hour. Going to the market, mopping the floor, standing to cook, carrying a baby, walking up the stairs all count. These small movements are called NEAT (non-exercise activity thermogenesis). Someone doing manual work and someone sitting in an office can differ by a few hundred calories a day, just from NEAT.
Try the Mifflin-St Jeor equation
Without lab equipment, people use estimation formulas. A commonly used one today is the Mifflin-St Jeor equation, published in 1990:
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Let us try it for a 30-year-old woman, 158cm tall, weighing 55kg:
- 10 × 55 = 550
- 6.25 × 158 = 987.5
- 5 × 30 = 150
- 550 + 987.5 − 150 − 161 = about 1,230 kcal
That is her BMR. To get TDEE, multiply by an activity factor:
| Activity level | Factor | TDEE in our example |
|---|---|---|
| Mostly sitting, hardly any exercise | 1.2 | about 1,470 kcal |
| Lightly active, exercise 1 to 3 times a week | 1.375 | about 1,690 kcal |
| Moderately active, exercise 3 to 5 times | 1.55 | about 1,900 kcal |
| Very active, exercise almost every day | 1.725 | about 2,120 kcal |
To picture it: a medium bowl of white rice is about 200 kcal. The gap between the first and last rows of the table is more than three bowls of rice a day.
Every number is only an estimate
The formula is built from measurements of many people, then averaged. You are one specific person.
For many people, the result is off by about 10% compared with a real measurement. For some, it is off by more. The reasons are very everyday:
- Muscle mass: of two people with the same weight, the one with more muscle usually has a higher BMR.
- Age: BMR tends to decline gradually with age.
- Sleep, health, weather, genetics: all of them can shift the number.
- The activity factor is self-rated: most of us tend to think we move a little more than we really do.
Smartwatches and apps are the same. The "calories burned" number on them is an estimate, not a direct measurement.
So think of BMR and TDEE as a compass, not a precision scale. It points you in a direction, while your own hunger, fullness and daily energy are the closest measurements you have.
What is TDEE good for?
Not for forcing yourself to eat very little. Knowing your TDEE helps you understand your body better:
- Understand why you are starving after a day of running errands. You are not greedy. The movement part of your TDEE just shot up.
- Read labels with a reference point. How much of your day's energy is a 600 kcal dish? Know your TDEE and you can answer that.
- Understand why the %DV column is not really about you. That column is based on a 2,000 kcal "reference day". Your needs may be higher or lower. More in what is %DV.
Just as important: eating far below your needs for a long time often leaves people tired, unfocused and irritable. Enough energy is the foundation of a good day.
Inside the kOBE kitchen
kOBE's slogan is "Eat what fits." We read it simply: everyone has different energy needs, so portions should fit each person too.
If you have estimated your TDEE, you can visit meal plans by calories and choose the level that suits your needs, instead of guessing.
And if you cook for yourself, all 1,480 home recipes on our recipe page list calories, protein, fat and sugar per 100g. Weigh your portion, multiply, and you will know how much of your TDEE that meal takes up.
Frequently asked questions
Can BMR change?
Is the "calories burned" number on my smartwatch accurate?
Should I eat differently on days off and work days?
Keep reading
Sources
- Mifflin M.D., St Jeor S.T. et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 51(2):241 to 247.
- FAO/WHO/UNU (2004). Human energy requirements. FAO Food and Nutrition Technical Report Series 1.
- National Institute of Nutrition (Vietnam) (2016). Recommended Dietary Allowances for Vietnamese People (Nhu cầu dinh dưỡng khuyến nghị cho người Việt Nam).
- Further reading: Understanding Nutrition 16th ed., chapter 8; Campbell B., Sports Nutrition.
