TDEE — Total Daily Energy Expenditure — is the total number of calories your body burns in a typical 24-hour period. It combines your Basal Metabolic Rate (BMR, the calories burned at rest) with all physical activity. TDEE is the critical foundation for any nutrition plan: eating above TDEE causes weight gain, eating below causes weight loss, and eating at TDEE maintains your current weight. Knowing your TDEE lets you set precise calorie targets for any body composition goal.