resting metabolic rate

In the 1780s for the French Academy of Sciences, Lavoisier, Laplace, and Seguin investigated and published relationships between direct calorimetry and respiratory gas exchanges from mammalian subjects. 100 years later in the 19th century for the Connecticut-based Wesleyan University, Professors Atwater and Rosa provided ample evidence of nitrogen, carbon dioxide, and oxygen transport during the metabolism of amino acids, glucose, and fatty acids in human subjects, further establishing the value of indirect calorimetry in determining bioenergetics of free-living humans.{{Cite book|url=https://archive.org/details/metabnitr00usde|title=Report of preliminary investigations on the metabolism of nitrogen and carbon in the human organism, with a respiration calorimeter of special construction|via=The Internet Archive|access-date=2016-03-07|publisher=Washington : Govt. Print. Off.|year=1897}}{{Cite book|url=https://archive.org/details/descriptionofnew63atwa|title=Description of a New Respiration Calorimeter and Experiments on the Conservation of Energy in the Human Body|via=The Internet Archive|access-date=2016-03-07|publisher=Washington : Govt. print. off.|year=1899}} The work of Atwater and Rosa also made it possible to calculate the caloric values of foods, which eventually became the criteria adopted by the USDA to create the food calorie library.{{Cite book|url=http://www.ucpress.edu/book.php?isbn=9780520280052|title=Why Calories Count|website=University of California Press|access-date=2016-03-03}}

In the early 20th century at Oxford University, physiology researcher Claude Gordon Douglas developed an inexpensive and mobile method of collecting exhaled breath (partly in preparation for experiments to be conducted on Pike's Peak, Colorado). In this method, the subject exhales into a nearly impermeable and large volume collection bag over a recorded period of time. The entire volume is measured, the oxygen and carbon dioxide content are analyzed, and the differences from inspired "ambient" air are calculated to determine the rates of oxygen uptake and carbon dioxide output.{{Cite journal|last=Cunningham|first=D. J. C.|date=1964-11-01|title=Claude Gordon Douglas. 1882-1963|journal=Biographical Memoirs of Fellows of the Royal Society|language=en|volume=10|pages=51–74|doi=10.1098/rsbm.1964.0004|doi-access=}}

To estimate energy expenditure from the exhaled gases, several algorithms were developed. One of the most widely used was developed in 1949 at University of Glasgow by research physiologist J. B. de V. Weir. His abbreviated equation for estimating metabolic rate was written with rates of gas exchange being volume/time, excluded urinary nitrogen, and allowed for the inclusion of a time conversion factor of 1.44 to extrapolate to 24-hour energy expenditure from 'kcal per minute" to "kcal per day." Weir used the Douglas Bag method in his experiments, and in support of neglecting the effect of protein metabolism under normal physiological conditions and eating patterns of ~12.5% protein calories, he wrote:

:"...In fact if the percentage of protein calories [consumed] lies between 10 and 14 the maximum error in using [the equation] is less than 1 in 500."{{Cite journal |doi = 10.1113/jphysiol.1949.sp004363|pmid = 15394301|pmc = 1392602|title = New methods for calculating metabolic rate with special reference to protein metabolism|journal = The Journal of Physiology|volume = 109|issue = 1–2|pages = 1–9|year = 1949|last1 = Weir|first1 = J. B. de V.}}File:Resting Metabolic Rate.png

In the early 1970s, computer technology enabled on-site data processing, some real-time analysis, and even graphical displays of metabolic variables, such as O₂, CO₂, and air-flow, thereby encouraging academic institutions to test accuracy and precision in new ways.{{Cite journal|last1=Beaver|first1=WL|last2=Wasserman|first2=K|last3=Whipp|first3=BJ|date=1973|title=On-line computer analysis and breath-by-breath graphical display of exercise function tests|journal=Journal of Applied Physiology|volume=34|issue=1|pages=128–132|doi=10.1152/jappl.1973.34.1.128|pmid=4697371}}{{cite journal|last1=Wilmore|first1=JH|last2=Davis|first2=JA|last3=Norton|first3=AC|title=An automated system for assessing metabolic and respiratory function during exercise|journal=Journal of Applied Physiology|date=1976|volume=40|issue=4|pages=619–624|doi=10.1152/jappl.1976.40.4.619|pmid=931884}} A few years later in the decade, battery-operated systems made debuts. For example, a demonstration of the mobile system with digital display of both cumulative and past-minute oxygen consumption was presented in 1977 at the Proceedings of the Physiological Society.{{cite journal|last1=Humphrey|first1=SJE|last2=Wolff|first2=HS|title=The Oxylog|journal=Journal of Physiology|date=1977|page=12|doi=10.1113/jphysiol.1977.sp011841|volume=267}} As manufacturing and computing costs dropped over the next few decades, various universal calibration methods for preparing and comparing various models in the 1990s brought attention to short-comings or advantages of various designs.{{cite journal|last1=Huszczuk|first1=A|last2=Whipp|first2=BJ|last3=Wasserman|first3=K|title=A respiratory gas exchange simulator for routine calibration in metabolic studies|journal=European Respiratory Journal|date=1990|volume=3|issue=4|pages=465–468|doi=10.1183/09031936.93.03040465|url=http://erj.ersjournals.com/content/3/4/465.full.pdf?|access-date=2016-03-07|pmid=2114308}} In addition to lower costs, the metabolic variable CO₂ was often ignored, promoting instead a focus on oxygen-consumption models of weight management and exercise training.

In the new millennium, smaller "desktop-sized" indirect calorimeters were being distributed with dedicated personal computers and printers, and running modern windows-based software.{{cite web|title=Angeion 2005 Annual Report -- page 7 -- Narrative Description of Business -- General|url=http://mgcdiagnostics.com/images/uploads/2005_10-KSB.pdf|website=MGC Diagnostics Company|publisher=MGC Diagnostics|access-date=2016-03-07}}

RMR measurements are recommended when estimating total daily energy expenditure (TEE). Since BMR measures are restricted to the narrow time frame (and strict conditions) upon waking, the looser-conditions RMR measure is more typically conducted. In the review organized by the USDA,{{cite web|title=Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) (2005)|url=http://fnic.nal.usda.gov/dietary-guidance/dri-nutrient-reports/energy-carbohydrate-fiber-fat-fatty-acids-cholesterol-protein|website=USDA|publisher=National Academy of Sciences, Institute of Medicine, Food and Nutrition Board|access-date=21 March 2016|url-status=dead|archive-url=https://web.archive.org/web/20160310031719/http://fnic.nal.usda.gov/dietary-guidance/dri-nutrient-reports/energy-carbohydrate-fiber-fat-fatty-acids-cholesterol-protein|archive-date=10 March 2016}} most publications documented specific conditions of resting measurements, including time from latest food intake or physical activities; this comprehensive review estimated RMR is 10 – 20% higher than BMR due to thermic effect of feeding and residual burn from activities that occur throughout the day.{{cn|date=January 2025}}

Thermochemistry aside, the rate of metabolism and an amount of energy expenditures can be mistakenly interchanged, for example, when describing RMR and REE.{{cn|date=January 2025}}

The Academy of Nutrition and Dietetics (AND) provides clinical guidance for preparing a subject for RMR measures,{{cite journal|last1=Raynor|first1=Hollie|last2=Champagne|first2=Catherine|title=Position of the Academy of Nutrition and Dietetics: Interventions for the Treatment of Overweight and Obesity in Adults|journal=Journal of the Academy of Nutrition and Dietetics|date=2016|volume=116|issue=1|pages=129–47|doi=10.1016/j.jand.2015.10.031|pmid=26718656|url=http://www.eatrightpro.org/resource/practice/position-and-practice-papers/position-papers/weight-management|access-date=21 March 2016|url-access=subscription}} in order to mitigate possible confounding factors from feeding, stressful physical activities, or exposure to stimulants such as caffeine or nicotine:{{cn|date=January 2025}}

In preparation, a subject should be fasting for 7 hrs or greater, and mindful to avoid stimulants and stressors, such as caffeine, nicotine, and hard physical activities such as purposeful exercises.

For 30 minutes before conducting the measurement, a subject should be laying supine without physical movements, no reading nor listening to music. The ambiance should reduce stimulation by maintaining constant quiet, low lighting, and steady temperature. These conditions continue during the measurement stage.

Further, the correct use of a well-maintained indirect calorimeter includes achieving a natural and steady breathing pattern in order to reveal oxygen consumption and carbon dioxide production rates under a reproducible resting condition. Indirect calorimetry is considered the gold-standard method to measure RMR.{{Cite journal|title = Indirect calorimetry: a practical guide for clinicians|journal = Nutrition in Clinical Practice|date = 2007-08-01|issn = 0884-5336|pmid = 17644692|pages = 377–388|volume = 22|issue = 4|first1 = Heather A.|last1 = Haugen|first2 = Lingtak-Neander|last2 = Chan|first3 = Fanny|last3 = Li|doi=10.1177/0115426507022004377}} Indirect calorimeters are usually found in laboratory and clinical settings, but technological advancements are bringing RMR measurement to free-living conditions.{{cn|date=January 2025}}

Long-term weight management is directly proportional to calories absorbed from feeding; nevertheless, myriad non-caloric factors also play biologically significant roles (not covered here) in estimating energy intake. In counting energy expenditure, the use of a resting measurement (RMR) is the most accurate method for estimating the major portion of Total daily energy expenditure (TEE), thereby giving the closest approximations when planning & following a Calorie Intake Plan. Thus, estimation of REE by indirect calorimetry is strongly recommended for accomplishing long-term weight management, a conclusion reached and maintained due to ongoing observational research by well-respected institutions such as the USDA, AND (previously ADA), ACSM, and internationally by the WHO.{{cn|date=January 2025}}

Energy expenditure is correlated to a number of factors, listed in alphabetical order.

• Age: Besides the epidemiologically correlated trends of aging, lowered physical activity, and loss of lean muscle mass,{{cite book|last1=Manore|first1=Melinda|last2=Meyer|first2=Nanna|last3=Thompson|first3=Janice|title=Sport Nutrition for Health and Performance|date=2009|publisher=Human Kinetics|location=United States of America|isbn=9780736052955|edition=2|url=https://us.humankinetics.com/products/sport-nutrition-for-health-and-performance-2nd-edition|access-date=30 October 2019}} lessened cellular activity (the senescence thereof) may also contribute to lowering of REE.{{Citation needed|date=April 2023}}

RMR is regularly used in ecology to study the response of individuals to changes in environmental conditions.

Parasites by definition have a negative impact on their hosts and it is thus expected that there might be effects on host RMR. Varying effects of parasite infection on host RMR have been found. Most studies indicate an increase in RMR with parasite infection, but others show no effect, or even a decrease in RMR. It is still unclear why such variation in the direction of change in RMR with parasite infection is seen.{{cite journal |last1=Robar |first1=Nicholas |last2=Murray |first2=Dennis L. |last3=Burness |first3=Gary |title=Effects of parasites on host energy expenditure: the resting metabolic rate stalemate |journal=Canadian Journal of Zoology |date=2011 |volume=89 |issue=11 |pages=1146–1155 |doi=10.1139/z11-084}}

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Category:Energy measurement

Category:Metabolism