Final answer:
Total energy expenditure varies most in the component related to physical activity, with potential differences being quite substantial depending on a person’s lifestyle and level of physical work.
Step-by-step explanation:
The component of total energy expenditure that varies most among individuals is the energy used in physical activity. While the basal metabolic rate (BMR) is generally consistent among people of similar size, gender, and muscle composition, the calories burned through movement and exercise can greatly differ based on lifestyle and occupation.
For example, an adult male leading a sedentary lifestyle might have a much lower energy expenditure from physical activity than someone who performs heavy work in a cold climate or an athlete, both of whom might need much more energy to support their increased level of physical activity. The variability can be significant, potentially spanning a range from around 20 percent to as much as 30 megajoules per day.