Editing Basal metabolic rate (section)

==Description==
The body's generation of heat is known as [[thermogenesis]] and it can be measured to determine the amount of energy expended. BMR generally decreases with age, and with the decrease in [[lean body mass]] (as may happen with aging). Increasing muscle mass has the effect of increasing BMR. [[Aerobic respiration|Aerobic (resistance)]] fitness level, a product of [[cardiovascular exercise]], while previously thought to have effect on BMR, has been shown in the 1990s not to correlate with BMR when adjusted for fat-free body mass.{{Citation needed|date=June 2011}} But [[Strength training|anaerobic exercise]] does increase resting energy consumption (see "[[Basal metabolic rate#Aerobic vs. anaerobic exercise|aerobic vs. anaerobic exercise]]").<ref name="pmid16526835">{{cite journal |vauthors=Stiegler P, Cunliffe A |title=The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss |journal=[[Sports Medicine]] |volume=36 |issue=3 |year=2006 |pages=239–262  |url=http://www.sportmedizin-hamburg.com/images/pdfs/Literatur_Verschiedene_Themen/Grundumsatzmessung_Stiegler2006.pdf  |pmid=16526835 |doi=10.2165/00007256-200636030-00005|s2cid=44212103 }}</ref>  Illness, previously consumed food and beverages, environmental temperature, and stress levels can affect one's overall energy expenditure as well as one's BMR.

[[File:Indirect calorimetry laboratory with canopy hood.jpg|thumb|Indirect calorimetry laboratory with canopy hood (dilution technique)]]

BMR is measured under very restrictive circumstances when a person is awake. An accurate BMR measurement requires that the person's [[sympathetic nervous system]] not be stimulated, a condition which requires complete rest. A more common measurement, which uses less strict criteria, is [[Resting metabolic rate|resting metabolic rate (RMR)]].<ref>
{{cite web |title=Calculating BMR and RMR: Diet and Weight Loss Tutorial  |website=CaloriesPerHour.com |url=http://www.caloriesperhour.com/tutorial_BMR.php |access-date=2008-01-26 |archive-url=https://web.archive.org/web/20080105084119/http://www.caloriesperhour.com/tutorial_BMR.php |archive-date=2008-01-05 |url-status=dead}}</ref>

BMR may be measured by gas analysis through either direct or [[indirect calorimetry]], though a rough estimation can be acquired through an equation using age, sex, height, and weight. Studies of energy [[metabolism]] using both methods provide convincing evidence for the validity of the [[respiratory quotient]] (RQ), which measures the inherent composition and utilization of [[carbohydrate]]s, [[fat]]s and [[protein]]s as they are converted to energy substrate units that can be used by the body as energy.