Energy In, Energy Out

A food Calorie is a unit of energy — technically a kilocalorie, the heat it takes to warm one kilogram of water by one degree Celsius. When a label reads 200 calories, it means that food provides about that much usable energy as your body breaks it down.

Most energy is spent before exercise even starts. BMR keeps you alive at rest and uses roughly 60-75% of daily burn; movement, workouts, and digestion make up the rest of TDEE.