Main Difference – BMR vs RMR
Metabolic rate is the amount of calories required to drive different mechanisms in the human body including fuel ventilation, blood circulation, and temperature homeostasis. Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) are the main metabolic rates used to assess the amount of calories a person will use if he/she is at rest for 24 hours. Gas analysis can be used to measure BMR and RMR through either direct or indirect calorimetry, although an approximate estimation of RMR can be developed through an equation using age, sex, height and weight. However, these terms are often used interchangeably. BMR is the minimal rate of energy expenditure per unit time by endothermic animals including human at rest time. The main difference between BMR and RMR is that BMR measurements take place under rigorous laboratory conditions and must meet total physiological balance whereas RMR conditions of measurement is an estimate of BMR under less rigorous conditions that can be altered and defined by the contextual limitations. However, BMR shares some similarities with RMR, but they do have some key differences. The purpose of this article is to highlight the difference between BMR and RMR.
What is BMR
BMR stands for Basal Metabolic Rate. BMR is also known as Basal Energy Expenditure or BEE. It is defined as the rate at which human body consumes energy when they are physically and mentally resting in order to maintain important body functions going such as breathing, cell division, growth and nerve cell functioning, etc. BMR measurements are characteristically taken in a stress-free, darkened room upon waking after 8-10 hours of sleep, 12 hours of fasting to make sure that the digestive system is not functioning, and with the subject resting in a relaxing position.
What is RMR
RMR stands for Resting Metabolic Rate. RMR is also known as Resting Energy Expenditure or REE. It is defined as the rate at which human body consumes energy when they are resting in order to maintain important body functions. RMR measurements are characteristically taken under less restricted conditions compare to BMR, and the subject is not required to spend the night sleeping in the test facility prior to RMR testing.
Difference Between BMR and RMR
Conditions of measurement
BMR is measured under very restrictive conditions.
RMR is measured under less restrictive conditions compared to BMR.
Requirement of a thermal neutral environment
BMR is measured under a thermal neutral environment, and it also needs a proper testing facility.
RMR is not measured under a thermal neutral environment, and it also does not need a proper testing facility.
Requirement of an 8 hour of sleep before measurement
BMR needs the subject to have at least 8 hours of sleep.
RMR does not need the subject to have at least 8 hours of sleep.
Requirement of Twelve hours of fasting
BMR requires the subject to fast for twelve hours before measurement.
RMR does not require the subject to fast for twelve hours of fasting before measurement.
Cheaper measurement
BMR assessment is more costly than RMR.
RMR assessment is cheaper than BMR assessment.
Realistic and easy measurement
BMR assessment is not an easy, and realistic measurement compared to RMR.
RMR assessment is an easy and realistic measurement compared to BMR.
Calorie estimations
BMR is slightly lower than RMR.
RMR is slightly higher than BMR.
Accuracy
BMR is more accurate than RMR.
RMR is less accurate than BMR.
Other names
BMR is also known as Basal Energy Expenditure.
RMR is also known as Resting Energy Expenditure.
Calculation formula
BMR: Harris–Benedict equation
- Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) – ( 4.7 x age in years )
- Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) – ( 6.8 x age in year )
RMR: Mifflin-St Jeor equation
- (RMR) kcal/day: (males) = 9.99 x weight (kg) + 6.25 x height (cm) – 4.92 x age(years) + 5;
- (RMR) kcal/day: (females) = 9.99 x weight (kg) + 6.25 x height (cm) – 4.92 x age (years) – 161.
In conclusion, both BMR and RMR are metabolic rates that estimate how many calories an individual would burn if he were to do nothing but rest for 24 hours. It represents the minimum amount of energy required to keep your body functioning.
References:
Müller, B; Merk, S; Bürgi, U; Diem, P (2001). Calculating the basal metabolic rate and severe and morbid obesity. Praxis (Bern 1994) 90 (45): 1955–63.
Johnstone, Alexandra M; Murison, Sandra D; Duncan, Jackie S; Rance, Kellie A; Speakman, John R; Koh, YO (2005). Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine. American Journal of Clinical Nutrition 82 (5): 941–948.
Ravussin, E; Lillioja, S; Christin, L; Bogardus, C; Bogardus, C (1986). Determinants of 24-hour energy expenditure in man. Methods and results using a respiratory chamber. The Journal of Clinical Invertigation 78 (6): 1568–1578.
Image Courtesy:
“Image 1” by Cosmed – Own work (CC BY-SA 3.0) via Commons Wikimedia
“Image 2” by Bmetabolism – Own work (CC BY-SA 4.0) via Commons Wikimedia
