Understanding BMR and TDEE Properly and Finding Your Right Calorie Target
When you start dieting, the first question you usually run into is, "How many calories should I eat per day?" The numbers differ from one YouTube video or app to another, so it is only natural to feel confused. In reality, the answer is not something someone else sets for you. It comes from the energy your own body uses each day. The two key concepts are basal metabolic rate (BMR) and total daily energy expenditure (TDEE). Today, we will calculate both directly and outline how to set your own appropriate calorie target.
| Section | Key summary |
|---|---|
| Introduction | In reality, the answer is not something someone else sets for you |
| What is basal metabolic rate (BMR)? | Basal metabolic rate (BMR) is the energy you burn even if you lie still all day and only breathe |
| Calculating BMR (Mifflin-St Jeor equation) | The most widely used and highly accurate formula is the Mifflin-St Jeor equation |
| TDEE: the total calories I actually use in a day | Short key point |
| Setting my right calorie target for fat loss | To lose 1kg of body fat, you need a calorie deficit of about 7,700kcal (intake < expenditure) |
| Nutrient distribution within a calorie deficit | Even at the same calorie level, what you fill those calories with matters |
| The trap of rapid weight loss: rebound and muscle loss | Short key point |
What is basal metabolic rate (BMR)?
Basal metabolic rate (BMR) is the energy you burn even if you lie still all day and only breathe. These are the calories used to sustain life, such as heartbeat, breathing, maintaining body temperature, and organ function. Surprisingly, about 60~70% of your total daily calorie burn comes from this. In other words, even without exercise, your body naturally uses quite a lot of energy. The reason having more muscle mass raises BMR is that muscle is tissue that uses energy even at rest.
Calculating BMR (Mifflin-St Jeor equation)
The most widely used and highly accurate formula is the Mifflin-St Jeor equation. You enter your weight (kg), height (cm), and age (years).
- Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
- Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
- Example) 30-year-old woman, height 162cm, weight 60kg → (10×60) + (6.25×162) − (5×30) − 161 = 600 + 1012.5 − 150 − 161 ≈ 1,302kcal
- Example) 35-year-old man, height 175cm, weight 75kg → (10×75) + (6.25×175) − (5×35) + 5 = 750 + 1093.75 − 175 + 5 ≈ 1,674kcal
TDEE: the total calories I actually use in a day
BMR is the number for when you are "only lying down." But in real life, we commute, walk, and exercise. TDEE (Total Daily Energy Expenditure) is the value obtained by multiplying BMR by your activity level, meaning the total calories you actually burn in a day. Diet calories should be set based on this TDEE, not BMR. It is calculated by multiplying BMR by an activity factor.
- Almost no movement (sedentary lifestyle): BMR × 1.2
- Light activity (exercise 1~3 times per week): BMR × 1.375
- Moderate activity (exercise 3~5 times per week): BMR × 1.55
- High activity (exercise 6~7 times per week): BMR × 1.725
- Example) The woman above (BMR 1,302) × 1.375 = about 1,790kcal as maintenance calories
Setting my right calorie target for fat loss
To lose 1kg of body fat, you need a calorie deficit of about 7,700kcal (intake < expenditure). So the key is "eating less than your TDEE," not simply starving yourself. A moderate deficit of about 300~500kcal per day below TDEE is usually recommended. For the woman above (TDEE about 1,790kcal), that would mean setting a target of about 1,300~1,500kcal per day. In theory, this allows weight loss at a healthy pace of about 0.3~0.5kg per week, or about 1.5~2kg per month.
Nutrient distribution within a calorie deficit
Even at the same calorie level, what you fill those calories with matters. During fat loss, getting enough protein is especially important to prevent muscle loss. In general, about 1.2~1.6g of protein per 1kg of body weight is recommended during a cutting phase (for example, about 72~96g for 60kg). Rather than cutting carbohydrates and fats to extremes, distribute them in a balanced way, and increase fullness with fiber-rich vegetables and whole grains so you can stay less hungry even on fewer calories.
- ① Calculate BMR using the Mifflin-St Jeor equation
- ② Multiply by an activity factor to find TDEE (maintenance calories)
- ③ Subtract 300~500kcal from TDEE to set your target calories
- ④ Secure protein first at 1.2~1.6g per kg of body weight
- ⑤ Fill the remaining calories with carbohydrates and fats, and add fullness with vegetables
- ⑥ Review weight changes over 2~4 weeks and fine-tune calories
The trap of rapid weight loss: rebound and muscle loss
Extreme restriction such as 800kcal per day may make weight drop quickly at first, but a large part of that lost weight is water and muscle. When muscle decreases, BMR falls with it, making it easier to hit a "plateau" and experience "rebound" later even when eating less. Also, if you reduce sleep or experience severe stress, ghrelin, the hunger hormone, rises and leptin, the satiety hormone, falls, increasing urges to overeat regardless of willpower. That is why getting enough sleep, around 7 hours, is also part of dieting.
In short, the most sustainable diet formula is to understand your basic energy expenditure through BMR, multiply it by your activity level to find TDEE, and then create a moderate deficit from there. The person who gets enough protein, sleeps well, and loses weight slowly is the one who ultimately stays the course. However, the calculations and guidance in this article are for general reference only and are not medical advice. If you have an underlying condition such as diabetes or thyroid disease, or if you are pregnant or breastfeeding, it is recommended that you consult a doctor or nutrition professional before restricting calories whenever possible.