Your metabolism is the set of chemical processes that keep your body alive. Understanding it - and the concept of Total Daily Energy Expenditure (TDEE) - is the foundation of any successful nutrition strategy.
What is Metabolism?
Metabolism converts the food you eat into energy. Even at rest, your body burns calories to keep your heart beating, lungs breathing, and brain functioning. This baseline burn rate is called your Basal Metabolic Rate (BMR).
BMR vs. TDEE
| Term | What It Measures |
|---|---|
| BMR | Calories burned at complete rest (zero activity) |
| TDEE | Total calories burned per day including all activity |
TDEE = BMR × Activity Multiplier
The Mifflin-St Jeor Equation
The most widely validated BMR formula for adults:
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Activity Multipliers
| Activity Level | Multiplier | Example |
|---|---|---|
| Sedentary | 1.2 | Office job, no exercise |
| Lightly Active | 1.375 | Light exercise 1–3 days/week |
| Moderately Active | 1.55 | Moderate exercise 3–5 days/week |
| Very Active | 1.725 | Hard exercise 6–7 days/week |
| Extremely Active | 1.9 | Physical job + training |
Using TDEE for Your Goals
- Lose weight: Eat 300–500 calories below TDEE
- Maintain weight: Eat at TDEE
- Gain muscle: Eat 200–300 calories above TDEE
The Thermic Effect of Food
Not all calories are equal in terms of metabolism. Protein has a thermic effect of 20–30% - meaning your body burns 20–30 calories just digesting 100 calories of protein. Fat is 0–3%, carbs are 5–10%.
Try the Calculator
Calculate your exact TDEE with our TDEE Calculator or Calorie Calculator.