TDEE
TDEE — Total Daily Energy Expenditure (TDEE) is the total number of calories a person burns in 24 hours. It is the sum of basal metabolic rate (BMR), the thermic effect of food (TEF), the energy cost of exercise (EAT), and non-exercise activity thermogenesis (NEAT). TDEE is the calorie target most weight management apps estimate to set deficits or surpluses.
What is TDEE?
TDEE — Total Daily Energy Expenditure — is the total calorie burn over 24 hours, integrating four components:
TDEE = BMR + TEF + EAT + NEAT
- BMR — Basal Metabolic Rate, the energy required to maintain life at complete rest (60-75% of TDEE for most adults)
- TEF — Thermic Effect of Food, the energy cost of digesting and metabolizing food (~10% of TDEE)
- EAT — Exercise Activity Thermogenesis, structured workouts (5-15% of TDEE)
- NEAT — Non-Exercise Activity Thermogenesis, all unstructured movement (5-50% of TDEE; the most variable component)
How is TDEE calculated?
The most common consumer approach is to estimate BMR from the Mifflin-St Jeor equation (Mifflin et al., 1990), then multiply by an activity factor:
- 1.2 — sedentary (desk job, no formal exercise)
- 1.375 — lightly active (light exercise 1-3 days/week)
- 1.55 — moderately active (moderate exercise 3-5 days/week)
- 1.725 — very active (hard exercise 6-7 days/week)
- 1.9 — extremely active (physical job + training)
The gold-standard reference method is doubly labeled water (DLW), which measures TDEE in free-living conditions over 1-2 weeks via stable isotope kinetics. Predictive equations carry typical errors of ±10-15% relative to DLW; activity-factor multipliers are the largest source of error because NEAT varies dramatically between individuals.
Why TDEE matters in calorie tracking
TDEE is the anchor for most weight management plans:
- Eat at TDEE → maintenance
- Eat 300-500 kcal below TDEE → ~0.5-1.0 lb/week loss
- Eat 300-500 kcal above TDEE → muscle gain (with adequate protein)
Because TDEE estimates carry inherent error, real-world weight trends should be used to refine the target every 2-4 weeks. Apps that lock users to a static TDEE estimate without adjusting for actual weight change tend to under-deliver on outcomes. See also BMR and RMR.