Which are the three components of total energy expenditure?

• A. Basal metabolic rate, the thermic effect of food, and activity energy expenditure.
• B. Resting energy expenditure, dietary thermogenesis, and metabolic turnover.
• C. Basal metabolic rate, dietary intake energy, and growth energy.
• D. Physical activity energy, adaptive thermogenesis, and sleep energy.

Answer: (A)

Total energy expenditure is the sum of energy used for life-sustaining functions at rest, the energy cost of processing the food we eat, and the energy spent on all physical activity. The resting or basal part covers the calories needed to keep organs, circulation, respiration, and basic metabolism going while awake but at rest. The thermic effect of food is the energy burned in digestion, absorption, and storage of nutrients. The energy for activity includes everything from planned exercise to everyday movement and fidgeting. This combination—resting energy expenditure, the thermic cost of food, and activity energy expenditure—best captures how our bodies allocate energy.

Other choices mix terms that aren’t typically used as a three-part framework, such as energy just for dietary intake or growth, or split out sleep energy or adaptive changes as separate components. The standard model groups energy for basic maintenance, food processing, and movement together as the three components.