#2: Overreporting the “extra” calorie expenditure of exercise
Most people count the calories they spend exercising as “extra” calories. There is a difference between calories burned while exercising and “extra” calories burned exercising. Here is an example: you burn 300 calories on the treadmill instead of your usual activity (watching TV at home); in reality, you have to subtract the calories you would have spent watching TV from these 300 calories to calculate how many additional calories you burned. Let’s say that watching TV, you would have burned 80 calories. In this specific case, you have expended 300 calories while exercising, and 220 “extra” calories.
Calorie counters mindlessly add the calories burned exercising as “extra” and in some cases, this practice can significantly influence the calorie calculations. Hence, calorie software counts the part of your usual activities that overlaps with the extra activities twice.
How to estimate the “extra” calories burned exercising?
In order to make the calculations more accurate, I shall first introduce the concept of MET values. MET values are a convenient way to calculate the calorie cost of activities. MET values are multiples of the resting energy expenditure per time. In plain English, a MET = 3 means burning 3 times more calories than resting. A MET = 1 signifies how many calories you burn at rest (your Resting Metabolic Rate or Basal Metabolic Rate). Whatever you do, you burn calories at a rate of at least MET = 1 with the only exception being sleeping which has MET = 0.9. During the day, most activities include sitting and walking which have MET values between 1.2 and 3. Your total daily energy expenditure is calculated by multiplying your Resting Metabolic Rate by the average MET of all your activities. Is your head spinning?
Let’s use a real world example. Consider a female person with a Resting Metabolic Rate of 1200 calories a day. One day has 1440 minutes. Our example lady is burning 1200/1440 = 0.84 calories per minute at rest, which signifies a MET = 1. Let’s say our example woman just returned from an aerobics class, where she exercised for 30 minutes. General aerobic class training has a MET = 6. Our example lady has just burned 30 (minutes) x 6 (MET) * 0.84 (calories per minute) = 151 calories while exercising. Suppose our lady would have chatted on the internet instead of exercising (MET = 1.5). In this example, the woman substituted chatting on the internet with aerobic exercising. Remember, that every time you do something you substitute one activity for another. In order to get the extra calories, we have to subtract 1.5 (chatting) from 6 (exercising). Now let’s calculate the extra calories: 30 (minutes) * (6 – 1.5) (MET value) * 0.84 = 113 calories.
Let’s consider what a standard calorie counter would have done. First, it will assume an average calorie burn rate of 1 calorie per minute. Then the counter will find that exercising for 30 minutes will yield 30 (minutes) * 6 (MET) * 1 (calories per minute) = 180 calories. The calorie counter will add these 180 calories to your daily expenditure without considering that a part of these 180 calories is already accounted by your usual activities.
Do you now see the difference between 113 calories and 180 calories? If that woman spends 5 hours a week in that aerobics class, the standard calorie counters will overreport her calorie output by: (180-113) * 10 = 670 calories a week. The woman will be fooled that her metabolic rate has dropped while she just overestimated her calorie expenditure. Enter weight loss plateau, wasted time and efforts. Do you have the time for trial and error calorie estimations?
Remember these two rules:
* Report only extra activities to your calorie counter. If your walk to your office every day, do not log “walking to office for 30 minutes” as an extra activity. Consider only unusual activities that contribute to extra expended calories!
* Always subtract the calories you would have burned instead of exercising. A general rule is to subtract from 1.2 to 1.5 from the MET values. In some cases, you need to subtract a greater MET. If you substitute 30 minutes of bodybuilding (MET = 6) for 30 minutes of slow jump rope (MET = 8) then the additional MET would be 8 – 6 = 2.
How to find the MET values of activities based on standard tables?
In order to make the above calculations, you need to know the MET values of activities. Standard tables give: name of activity, duration and calories. Standard tables assume an average calorie expenditure of one calorie per minute. To find the MET you just need to divide the calories by the duration.
Example: “Bicycling, stationary, general”, “20 minutes”, “140 calories”
MET of “Bicycling, stationary, general” = 140 / 20 = 7
I know these calculations are somewhat tedious and in many cases the standard calorie calculations are close to correct. However, in some cases they can significantly over or under-calculate the calorie expenditure of activities and compromise your weight loss plan with daily miscalculations.