Understanding Total Energy Expenditure and the Importance of Basal Metabolic Rate

For the typical person, which variable contributes the most to total energy expenditure?

Final answer:

The basal metabolic rate (BMR) contributes the most to total energy expenditure, accounting for about 75% of daily calories burned, influenced by factors such as age, gender, body weight, and muscle mass.

Explanation:

The variable that contributes the most to total energy expenditure for a typical person is the basal metabolic rate (BMR), which accounts for about 75% of the calories burned in a day. The BMR is primarily divided among various systems in the body, with the largest fraction being used by the liver and spleen, followed by the brain.

This rate varies with several factors, including age, gender, body weight, and muscle mass, with muscle mass having a higher calorie burn rate than body fat. For instance, athletes, due to their greater muscle mass, generally have a higher BMR. When engaging in vigorous exercise, the energy consumption of the skeletal muscles and heart markedly increases, but these are not the primary contributors to the daily energy expenditure under normal circumstances.