MadSci Network: Biochemistry

Re: how do scientists measure the amount of calories burned during activities ?

Date: Fri May 26 18:09:49 2000
Posted By: Phyllis Stumbo, Staff, Nutrition, University of Iowa
Area of science: Biochemistry
ID: 958740800.Bc

When the body "burns" food to produce energy, oxygen is used and carbon 
dioxide and heat are produced.  Scientists have developed ways to measure 
the amount of calories burned in activities by measuring either of these 3 
components.  The most precise is the room calorimeter where a subject may 
remain for several days and the amount of heat produced by the body is 
determined by measuring how much heat is absorbed by the surrounding walls.  
This is a very technical process and not easily done, but there are at 
least three centers in the United States where this is measured.

It is much more common to measure either the amount of oxygen consumed or 
carbon dioxide produced.  Exhaled air is collected during exercise and 
the amount of oxygen used is determined.  This is also a tedious process 
and requires an oxygen analyzer.  Interesting the amount of air that 
is exhaled compares well with the amount of energy used, so a short-cut 
method to measuring energy expenditure is measure the amount of air exhaled 
and compare to a the volume expired in experiments when oxygen was actually 
measured.  This is not as exact, but gives useful information.  It has even 
been proposed to simply count the number of breaths taken since this also 
correlates to energy expended, but you can see this would be even less 

All of these methods require the use of equipment that is bulky.  
Scientists have searched for easier methods to measure energy expenditure.  
Some devices measure the amount of movement, such as a pedometer that 
measures steps or accelerometer that measures movements, to estimate energy 
expenditure.  This is less accurate, but very practical and yields useful 

Phyllis Stumbo
University of Iowa

Current Queue | Current Queue for Biochemistry | Biochemistry archives

Try the links in the MadSci Library for more information on Biochemistry.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2000. All rights reserved.