Leading a healthy lifestyle means eating healthfully and getting physical activity. How you live your life influences your daily caloric burn. Resting metabolic rate, or RMR, is the term used to describe the amount of calories your body uses at rest.
Resting Metabolic Rate
RMR is the total number of calories needed to keep the body in its homeostatic state during rest. According to "The Health Fitness Instructor's Handbook" by Edward Howley and B. Don Franks, RMR accounts for 60 to 70 percent of a your daily caloric need. Your metabolic rate can be determined by heat production by the body. "Exercise Physiology" by Books, Fahey and Baldwin states that heat is produced by all of the processes occurring inside the body, which is metabolism.
The Calorie
One calorie is the amount of heat required to raise the temperature of one gram of water one degree Celsius. Because metabolism is basically heat production, units of calories measure energy use. According to Brooks, Fahey and Baldwin, heat is measured to determine metabolic rate. Calorimetry is the measurement of heat by which one calculates metabolic rate. Resting metabolic rate can be determined through direct calorimetry, indirect calorimetry or by estimation using an equation.
Measuring Resting Metabolic Rate: Direct and Indirect Calorimetry
As previously stated, heat is produced when the body takes energy to maintain all of its processes. Direct calorimetry involves the direct measurement of heat and is very difficult to do, state Brooks, Fahey and Baldwin. Therefore, it is recommended to take part in indirect calorimetry or by using an equation to estimate. Indirect calorimetry is the measurement of oxygen consumption. Since metabolism takes oxygen, measuring the amount of oxygen used can provide an accurate measurement of resting metabolic rate. Indirect calorimetry should be done in a lab with the assistance of professionals.
Measuring Resting Metabolic Rate: Estimating
Another way to personally estimate resting metabolic rate is through an equation developed by professionals. Having resting metabolic rate tested in a lab is not always an option for the average person. Howley and Franks state that a number of equations have been written for the purpose of estimating resting metabolic rate. The equations below take into account gender, body size and age in order to estimate resting metabolic rate.
For males - RMR = 66 + (five x height) + (13.8 x weight) - (6.8 x age).
For females - RMR = 655 + (1.8 x height) + (9.6 x weight) - (4.7 x age).
Influences
According to Howley and Franks there are three main factors that influence RMR. The first is size. The larger you are, the more calories you need. RMR decreases with age--after 45 years RMR decreases substantially. Finally, body composition influences RMR. Since muscle is more metabolically active than fat, the more lean body mass your have, the higher your metabolic rate.
Changing Resting Metabolic Rate
Of the three factors listed above, body composition is the most changeable. Through exercise and healthy eating, you can change your body composition. Aerobic and resistive exercise programs can help decrease fat mass and increase lean body mass, leading to a higher resting metabolic rate.
References
- "The Health Fitness Instructor's Handbook"; Edward T. Howley, B. Don Franks; 2003
- "Exercise Physiology"; George A. Brooks, Thomas D. Fahey, Kenneth M. Baldwin; 2005
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