Understanding and Using MET Values

The Compendium of Physical Activities Tracking Guide lists MET values for over 600 different activities. Each activity listed in the Compendium has the following information: compcode, MET value, category heading, and description. For most activities, MET values are provided for two different years: 1993 and 2000. This is because the Compendium was first published in 1993 and updated to include revised and additional MET values in the year 2000. When the MET values between 1993 and 2000 differ, use the year 2000 MET value unless there is a reason to do otherwise.

Excerpt from Compendium

Here is what the layout of the Compendium looks like (excerpts of information are for the activities of raking leaves, walking at 3 mph, and sitting quietly and watching TV).

1993
2000
 
compcode
METS
compcode
METS
heading
description
08160
4.0
08160
4.3
lawn and garden
raking lawn
17190
3.5
17190
3.3
walking
walking, 3 mph, level, moderate pace, firm surface
07020
1.0
07020
1.0
inactivity quiet
sitting quietly and watching TV

Meaning of MET

MET stands for "metabolic equivalent" and is defined as "the ratio of the work metabolic rate to the resting metabolic rate" (Ainsworth). One (1) MET is the rate at which adults burn kcal at rest: This is approximately 1 kcal per kilogram of body weight per hour (expressed as 1 kcal/kg/hr). Thus, the MET value of "sitting quietly and watching TV" is "1," whereas the MET value of "walking on level ground at moderate pace" is 3.3 (see table below). In other words, sitting quietly burns 1 kcal/kg/hr whereas walking on level ground at a moderate pace burns 3.3 kcal/kg/hr.

MET values also are defined as "multiples of resting metabolic rate." Thus, sitting quietly watching TV burns no more kcals than are needed for resting whereas walking at a moderate pace burns 3.3 times as many kcals as are needed for resting (or sitting quietly).

Using MET Values

To use the MET values directly from the Compendium, you must know the individual's body weight in kg. Since 1 kg = 2.2 lb, weight in lb can be converted to weight in kg by dividing "weight in lbs" by "2.2 lb/kg." Example for 132 lb individual:

132 lb = 60 kg
2.2 lb/kg

The total kcal expended by an individual of a certain body weight (e.g., 60 kg) who engages in a given activity (e.g., raking lawn) for a specified length of time (e.g., 45 minutes, which is .75 hr) is calculated by multiplying together 3 numbers:

MET value of activity x body weight in kg x time in hours

For the previous example of raking lawn, the calculation and respective total kcal expended are:

4.3 kcal/kg/hr x 60 kg x .75 hr = 193.5 (194) kcal.

Converting MET Values to Use with Body Weight in Pounds (lb).

Any MET value in the Compendium can be converted to provide the kcal expenditure per lb as opposed to per kg. Since 1 kg = 2.2 lbs, simply divide the MET value by "2.2." Example for raking leaves (MET value of 4.3):

4.3 = 1.95 (kcal/lb/hr)
2.2

To calculate total kcal expended by a 132 lb (60 kg) person who rakes leaves for .75 hr:

1.95 kcal/lb/hr x 132 lb x .75 hr = 193 kcal

Note the answer--total kcal expended by a 132 lb (60 kg) person who rakes the lawn for .75 hr--comes out basically the same regardless of whether you are using the actual MET value (kcal/kg/hr) or the converted MET value (kcal/lb/hr).

Extensive information on making these conversions for walking is given by Walking Kcal Expenditure.

Calculating Additional Kcal Burned

Another question that can be answered through using the MET values is:

"How many additional kcal will be burned by replacing one activity with another?"

When an individual attempts to increase his/her physical activity level, she usually replaces a very sedentary activity (e.g., sitting quietly and watching TV) with a more vigorous activity. To calculate the additional kcal burned by substituting a more vigorous activity for a sedentary activity, simply complete the following two steps:

(a) calculate the difference between (subtract) the greater MET value and the smaller MET value
(b) calculate the additional kcal expended by multiplying together "difference in MET values" x "body weight" x "time"
Here is an example calculation of the additional kcal expenditure for a 60 kg adult who substitutes raking leaves for sitting quietly for .75 hours:

(a): 4.3 kcal/kg/hr - 1 kcal/kg/hr = 3.3 kcal/kg/hr
(b): 3.3 kcal/kg/hr x 60 kg x .75 hr = 148.5 (149) kcal

Extensive information is given on additional kcal burned by walking in Walking Kcal Expenditure