Energy expenditure refers to the total amount of energy that a person uses in a given period, typically measured in calories. This energy is required for various bodily functions, including maintaining body temperature, supporting organ function, and facilitating physical activity. Energy expenditure can be categorized into three main components: basal metabolic rate (BMR), physical activity, and the thermic effect of food. BMR accounts for the majority of energy expenditure, as it represents the energy needed for basic life-sustaining processes while at rest. Physical activity varies widely among individuals and includes all movements, from exercise to daily tasks. The thermic effect of food refers to the energy used in digestion and metabolism of the food consumed.