TDEE is the total number of calories you burn per day, including BMR (calories at rest), physical activity, and digestion. It's your maintenance calories - eat this amount to maintain weight. Example: 30-year-old male, 180 lbs, moderately active has TDEE of ~2,700 calories/day.
- BMR (60-70% of TDEE): Calories burned just existing (breathing, circulation)
- Physical Activity (15-30%): Exercise + daily movement (walking, stairs)
- TEF (10%): Thermic Effect of Food (energy to digest food)
- NEAT: Non-Exercise Activity Thermogenesis (fidgeting, standing)
TDEE varies based on age, sex, weight, height, and activity level. It changes as your weight changes - recalculate every 10-15 lbs lost or gained. Your TDEE is roughly your "maintenance calories" where you neither gain nor lose weight.