# Counting calories? Using METs for accuracy.

It seems everywhere you turn within the Internet community, there are websites offering inaccurate, third-hand, unsourced information on counting calories. Calculating how many calories your body needs daily is a cornerstone of proper weight management. A key component of this process is determining the caloric expenditure of your preferred regular physical activity. This is where the data online can get rather fuzzy. To offer some clarification, it's worth looking at METs and RMR, two essential concepts in tallying calories.

Caloric expenditure between two individuals performing the same task at the same rate (e.g., running at 10:00 mile pace or 6 mph) differs based on body weight. A heavier person will burn more calories over a given time than a lighter person. Physical activity is therefore measured in METs, or metabolic equivalents. One MET is equal to your resting metabolic rate (RMR), the amount of energy expended sitting quietly. This, too, differs among people, but the ratio of a given activity to it does not. Therefore, METs measure various physical activities as multiples of RMR. Running at 10:00 mile pace costs 10 METs--it expends 10 times the energy of sitting quietly. Factoring in your RMR, body weight, and the length of time performing the activity will give you a reliable number of calories burned.

One trusted (and downloadable) source of MET values for an exceptionally diverse array of physical activities is The Compendium of Physical Activities Tracking Guide (http://prevention.sph.sc.edu/tools/docs/documents_compendium.pdf). Together with the following formula, known as the Mifflin equation for RMR, you can calculate your RMR and determine fairly accurately the caloric cost of your workouts.

For men:

(10 x w) + (6.25 x h) - (5 x a) + 5 = RMR in calories burned over 24 hours

For women:

(10 x w) + (6.25 x h) - (5 x a) - 161 = RMR in calories burned over 24 hours

Where:

w = weight in kg (your weight in pounds divided by 2.2)

h = height in cm (your height in inches multiplied by 2.54)

a = age

The equations do not take into account the percentages of muscle and fat composing your body. It's therefore less accurate if you have a non-typical amount of muscle, because muscle burns calories while you're at rest, and fat does not. A person with an above average amount of muscle will therefore have a higher RMR than calculated; a person with a below average amount of muscle will have a lower RMR than calculated.

Next, divide the resulting number by 24 to establish your RMR over one hour. Multiply that value by the number of METs your chosen activity expends, according to the Tracking Guide. This is the number of calories you personally burn per hour performing this activity.

Note that when tallying a days' worth of energy, you must factor in lifestyle exercise, the energy spent walking around or performing chores. There is also what is known as the thermal effect of food, a small amount of calories burned by eating and digesting. Any weight loss plan can be established by simply plugging in your goal weight into the RMR formula. It is generally advised that you do not attempt to lose more than two pounds per week. Since one pound of body weight equals 3,500 calories, this means cutting up to 1,000 calories per day is considered safe (1,000 x 7 = 2 pounds per week). Remember too that increased lean muscle mass will raise your RMR over time, giving your weight loss a natural boost.
Sample Exercise METs

Weightlifting (general "light or moderate")            3.0 METs
Walking (3.5 mph or "brisk" on a level, firm surface)  3.8 METs
Tennis (singles)                                       7.0-8.0 METs
Cycling (200 watts or "vigorous" stationary)           10.5 METs
Running (8:00 mile pace or 7.5 mph)                    12.5 METs

Sample Lifestyle METs

Washing Dishes (standing)                              2.3 METs
Golf (walking, carrying clubs)                         4.5 METs
Gardening (digging, spading, composting)               5.0 METs
Dancing (aerobic, general)                             6.5 METs

The consensus among health care professionals is that activities
burning 3.0 to 6.0 METs qualify as moderate intensity; those using more
than 6.0 METs are considered vigorous.

The Centers for Disease Control and Prevention, http://www. cdc.gov

The Compendium of Physical Activities Tracking Guide, 2000, http://prevention.sph.sc.edu/tools/does/documents_compendium.pdf

Calories Per Hour, http://www.caloriesperhour.com/tutorial_BMR.php
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