Which of the following is used to measure body metabolism?

The measurement of body metabolism is fundamentally linked to energy expenditure, which is expressed in calories. Calories represent the amount of energy required to raise the temperature of one gram of water by one degree Celsius. In the context of human metabolism, this measurement reflects the energy that the body uses to perform various functions, such as maintaining bodily processes at rest (basal metabolic rate), as well as during physical activity.

While joules are also a unit of energy and can measure metabolism, calories are more commonly used in nutrition and fitness contexts, making them the more noteworthy choice when discussing body metabolism specifically. The other options, such as pounds and liters, do not represent energy or metabolic rate and therefore do not apply to the measurement of body metabolism.