Britannica Sources used in this answer

How is basal metabolic rate measured under standardized conditions?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

USDA MyPlate dietary guidelines — human nutrition MyPlate, a revised set of dietary guidelines introduced by the U.S. Department of Agriculture (USDA) in 2011, divides the four basic food groups (fruits, grains, protein, and vegetables) into sections on a plate, the size of each section representing the relative dietary proportions of each food group. The small blue circle shown at the upper right illustrates the inclusion and recommended proportion of dairy products in the diet.

The basal metabolic rate (BMR) is a precise measure of the energy required to support basic life functions. To ensure accuracy, it is measured under strictly controlled, standardized conditions: the individual must be at absolute rest (but not asleep), shortly after awakening in the morning, at least 12 hours after their last meal, and in a room with a comfortable temperature.12

Because these conditions are difficult to maintain, BMR is rarely measured in practice. Instead, researchers often determine the resting energy expenditure (REE), which is measured under less stringent conditions—typically 2 to 4 hours after a meal—and serves as a close proxy for BMR.2

Energy expenditure is assessed using two primary methods:
* Direct calorimetry: Measures heat dissipated from the body using specialized equipment like insulated chambers or water-cooled garments.2
* Indirect calorimetry: The more common, less cumbersome technique, which calculates heat production based on measurements of oxygen inhaled, carbon dioxide exhaled, and urinary nitrogen excreted.2