Back to Health & Fitness

Understanding TDEE: How Your Body Burns Calories

7 min read

Understanding TDEE: How Your Body Burns Calories

Whether you are trying to lose weight, build muscle, or simply maintain your current physique, understanding how your body uses energy is the foundation of any nutrition plan. Total Daily Energy Expenditure (TDEE) is the single most important number in that equation. It represents the total number of calories your body burns in a 24-hour period, accounting for everything from breathing to intense exercise.

The Three Components of TDEE

Your daily calorie burn is not one monolithic process. It breaks down into three distinct components, each contributing a different share of the total.

1. Basal Metabolic Rate (BMR) -- 60 to 70%

Your BMR is the energy your body needs to perform basic life-sustaining functions while completely at rest: pumping blood, breathing, maintaining body temperature, and repairing cells. For most people, BMR alone accounts for the majority of daily calorie expenditure. Even if you spent the entire day in bed, your body would still burn this amount.

Factors that influence BMR include:

  • Age -- BMR tends to decline roughly 1-2% per decade after age 20
  • Sex -- Males generally have a higher BMR due to greater lean muscle mass
  • Body composition -- More muscle mass raises BMR; more fat tissue lowers it
  • Genetics -- Individual metabolic variation can account for 200-300 calorie differences between people of similar size

2. Thermic Effect of Food (TEF) -- About 10%

Digesting, absorbing, and metabolizing food itself requires energy. This is known as the thermic effect of food. Protein has the highest thermic effect (20-30% of its calories are used during digestion), followed by carbohydrates (5-10%) and fats (0-3%). This is one reason high-protein diets can be advantageous for weight management -- you effectively "lose" more calories during digestion.

3. Physical Activity and Exercise -- 15 to 30%

This component includes both structured exercise (running, weight training, cycling) and non-exercise activity thermogenesis (NEAT) -- the calories burned through fidgeting, walking to the kitchen, standing, and other daily movement. For sedentary individuals, this component may be as low as 15%. For highly active people, it can exceed 30%.

How BMR Is Calculated

Two widely used formulas estimate BMR from basic measurements:

Mifflin-St Jeor Equation (generally considered more accurate for modern populations):

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

Harris-Benedict Equation (the original, revised in 1984):

  • Men: 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age)
  • Women: 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age)

Most nutrition professionals now prefer the Mifflin-St Jeor equation because studies have shown it predicts measured resting metabolic rate within 10% for the majority of individuals.

Activity Multipliers

Once you have your BMR, you multiply it by an activity factor to estimate TDEE:

  1. Sedentary (little or no exercise): BMR x 1.2
  2. Lightly active (exercise 1-3 days/week): BMR x 1.375
  3. Moderately active (exercise 3-5 days/week): BMR x 1.55
  4. Very active (hard exercise 6-7 days/week): BMR x 1.725
  5. Extremely active (physical job + intense training): BMR x 1.9

For example, a moderately active 30-year-old male weighing 80 kg and standing 178 cm tall would have a BMR of approximately 1,780 calories and a TDEE of about 2,759 calories.

Using TDEE for Your Goals

  • Weight loss: Eat 300-500 calories below your TDEE for a sustainable deficit of roughly 0.25-0.5 kg (0.5-1 lb) per week. Deficits larger than 500 calories risk muscle loss and metabolic adaptation.
  • Maintenance: Match your calorie intake to your TDEE to keep your weight stable.
  • Weight gain / muscle building: Eat 250-500 calories above your TDEE, paired with a resistance training program, to support lean mass growth while minimizing fat gain.

Common Mistakes to Avoid

  • Overestimating exercise calories. Fitness trackers and gym machines often inflate calorie burn by 20-50%. Use conservative estimates.
  • Underestimating food intake. Studies show people routinely underreport calorie consumption by 20-40%. Weigh and measure portions, especially during the learning phase.
  • Choosing the wrong activity level. Be honest about your weekly routine. A desk job with three gym sessions is "lightly active," not "very active."
  • Ignoring adaptation. As you lose weight, your TDEE drops. Recalculate every 4-6 weeks to keep your plan on track.

Practical Tips

  • Track your intake for two weeks at your estimated TDEE and monitor your weight trend. Adjust by 100-200 calories if your weight is not responding as expected.
  • Prioritize protein intake (1.6-2.2 g per kg of body weight) to preserve muscle mass and benefit from the higher thermic effect.
  • Focus on consistency over perfection. A small daily deficit maintained for months will always outperform an aggressive crash diet followed by a rebound.

Related Calculators