Metabolic Rate,
Resting Metabolic Rate
& Total Energy Expenditure

"Metabolic rate" is an imprecise term, that too often is misused, which confuses (or misleads) the reader rather then imparting accurate information and understanding. When you read, or hear, "metabolic rate" your first question should be, "what are they actually referring to?"

Most often "metabolic rate" is meant to refer to the RMR/REE/BMR component of your daily total-energy-expenditure. Less often (but frequently) it conflates RMR/REE/BMR with another fraction of total-energy-expenditure like TEF or EPOC. These mistakes underlie misleading claims, like "exercise increases your metabolism" or eating breakfast "revs up your metaboism." In both cases the claim is false regarding the effect of exercise or eating on RMR/REE/BMR which by definition are separate from the energy expenditure of either physical activity or digestion.

TOTAL ENERGY EXPEDITURE (TEE) is the sum total of all the energy your body uses throughout the day. TEE is on average 1.6 times your RMR (1.2- to 1.9, or more) and consists of the following: 

• RMR/REE - RMR consists of the (energy) cost of involuntary activities necessary to sustain life (liver and kidney functioning, heart pumping, etc., etc.) RMR typically represents 65- to 75-percent of a person's total metabolism (total energy expenditure). Another common (interchangeable) term for RMR is "resting energy expenditure" (REE). See the conditions for "Accurately Measuring RMR" below. Note that RMR includes the slightly smaller fractions of energy expenditure BMR and SMR.

-BMR (Basal Metabolic Rate) is about 10% lower than RMR because it is measured just upon waking (having slept at the metabolic lab), before even moving around (also under the research setting conditions for measuring RMR).

-SMR (Sleeping Metabolic Rate) is still lower than BMR (~5% lower), and is the slowest that human metabolism drops to.(ii)

• TEF - is the energy cost associated with digesting and assimilating what we eat. Both balanced diets and high-carbohydrate diets are associated with an average TEF of ~10%, while for a "balanced" high protein diet (35/35/30, CHO, PRO, FAT respectively) the TEF will amount to ~12% of calories ingested. Other terms for TEF include: DIT, SDA. Go to Thermic Effect of Food for further details.

• Physical Activity - The energy cost of all body movement, including exercise, and even the muscle tone necessary for sitting. Your energy expenditure in voluntary (or work related) physical activity is the most variable component of TEE. The following components of EE fall within this category:

-NEAT (Non-exercise-activity thermogenesis) for example, figeting, or paceing. 

-PAEE (Physical-activity-energy-expenditure) like running or playing tennis, etc. This category is generally thought to be activities that you voluntarily choose to engage in for either sport or physical fitness.

-ADL (activity of daily living) lifestyle physical activity like doing dishes, brushing your teeth, organizing a closet, using stairs, or parking on the outer edge of a parking lot for a longer walk in/out of a store. 

-EPOC (Excess-post-exercise-oxygen-consumption) which is basically an "afterburn" effect where the body continues to burn a few extra calories while it recovers (muscle repair and glycogen restoration) from high-intensity PA.

Accurately Measuring RMR
In research settings, RMR is measured as follows:

• in a thermoneutral room (79 to 84° F)
• at least 12-hours after eating
• at least 12-hours after exercising (to avoid having the reading skewed upward by any residual post-exercise-oxygen-consumption [PEOC]
• while the subject is reclined and resting

When RMR is measured under other conditions it generally will be skewed upward because of the effects of either activity, digestion, or even mental stimulation. For example, one study by University of Colorado (sponsored by HealtheTech, the company that first brought the MedGem and BodyGem RMR-analyzers to market) showed that RMR measured in the afternoon "after a 4-hour fast and exercise" averaged 100-calories more than a morning measurement.(i)

If the above conditions are not followed you are not getting a true (accurate) RMR measurement.

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i. Haugen, HA, et. al. Variability of measured resting metabolic rate. AJCN 2003;78:1141-4.
ii. Westerterp KL. Diet induced thermogenesis. Nutr & Metab 2004;1(5)