What type of energy expenditure is primarily affected by body composition?

The primary type of energy expenditure that is significantly influenced by body composition is resting energy expenditure (REE). REE refers to the amount of energy expended by the body at rest to maintain essential physiological functions, such as breathing, circulation, and cell production.

Body composition plays a major role in determining REE because lean body mass, which includes muscles and organs, is metabolically more active than fat mass. Essentially, individuals with a higher proportion of muscle mass will have a higher resting energy expenditure compared to those with a higher proportion of fat mass. This is because muscle tissue requires more energy to sustain itself than adipose (fat) tissue does.

In contrast, while the other energy expenditure categories like the thermic effect of food or physical activity expenditure can also be influenced by body composition, their dependency on body composition is not as direct or significant as that of resting energy expenditure. Total Energy Expenditure (TEE) considers all forms of energy expenditure (including REE, thermic effect of food, and physical activity), so while body composition can influence TEE, it is not the primary aspect that is primarily affected when looking at energy expenditure in isolation.