What is indirect calorimetry and how does it work?
Indirect calorimetry measures resting metabolic rate, or the number of calories your body burns at rest.  It can also measure how many calories your body burns after eating.

The test involves measuring the amount of oxygen a subject breathes in, and the amount of carbon dioxide (CO2) breathed out.  From these gas exchange data, the number of calories burned per minute is determined. 

The test is done by having the subject lie comfortably in bed, while wearing a large, clear “bubble”, or canopy, over the head and neck.  The canopy is ventilated, lightweight and comfortable. 

Testing conditions
Subjects are required to fast for 10-12 hours prior to a resting metabolic rate test, and to lie quietly for the duration of the test. The subject breathes normally, and watches TV or a movie to keep from falling asleep.  Sleeping, moving, laughing, sitting up, etc, produce inaccurate results.

How long does an indirect calorimetry test take?
A measurement of resting metabolic rate takes about 45 minutes.

A measurement of the number of calories burned after eating takes 5-6 hours, however only 30 minutes of each hour are spent under the canopy.  During the other 30 minutes of each hour, the subject can read, work on a computer, read, etc.

Who makes the indirect calorimeter?
The indirect calorimeter housed in the lab is the MAX-IIa Metabolic Cart System made by AEI Technologies (www.aeitechnologies.com) in Illinois.