Final answer:
A water-filled chamber used to measure basal metabolic rate is known as a whole-body calorimeter, which has been instrumental in understanding human metabolism.
Step-by-step explanation:
A water-filled chamber into which someone is placed in order to measure her basal metabolic rate is called a whole-body calorimeter. They can be in the form of whole-body calorimeters or whole-room calorimeters, depending on the size and level of activity being measured.
The basal metabolic rate (BMR) is the energy expenditure of a person at rest in a neutrally temperate environment, 10-12 hours after eating. It represents the minimum amount of energy needed to maintain essential physiological functions such as heartbeat, respiration, and kidney function. Historically, the direct measurement of BMR was done using a device such as the Atwater calorimeter, where a person could live and work for several days. Such calorimeters have been instrumental in proving that the human body operates on the combustion of fuels, similar to an engine. Although they are not commonly used now due to technical difficulties, the concept established by Atwater's experiments remains foundational. Nowadays, whole-room calorimeters enable the measurement of an individual's metabolism during normal activities, offering insights applicable to real-world conditions. They are valuable in understanding metabolic rates under various conditions, including different environmental factors, diets, and health statuses.