Good evening,

In this newsletter, we’ll talk about **how many calories you’re REALLY burning** on the fitness machines.

After a full hour jog, you look on the treadmill, you check the number of calories burned, and the magic number is 637 calories. Not bad for an hour on the treadmill. But how accurate is this? Let\’s examine this.

First of all, what is a calorie? A calorie is a measure of the amount of energy it takes to heat up 1 liter of water by 1 degree Celsius. Put simply, it\’s basically a measure of energy.

Now what affects how much energy you expend? Here is a list just off the top of my head: age, fitness level, speed, total weight, fat-free weight, muscle mass, speed of metabolism, incline, heart rate, hormones, clothes you\’re wearing, temperature in the room, and even your thoughts during the time you are on the treadmill. This list is far from complete, but it\’s a good place to start.

Just to give a quick example of how different people will burn different amounts of calories. Let\’s say you have 2 women, both of them 40 years old, both of them 1.62 metres tall (5\’4), both of them weigh 150 lbs. and they are both walking at 3.5 miles per hour. One woman has 15% body fat, whereas the other woman has 35% body fat. In other words, everything is identical except for this one factor. Do you really think both women will burn the same number of calories? Heck no!

Another example: Let\’s say you have 2 men, both of them 25 years old, both of them 1.77 metres (5\’10 or so) tall, both weigh 180 lbs, and both of them have 12% body fat. They are both jogging at a speed of 6 miles per hour. One of them has a heart rate of 170 at this speed, and the other one has a heart rate of 130 at this speed. In other words, one of these men is expending significantly more ENERGY (that is, calories) to maintain this pace than the other. But in the end, what does the number on the treadmill (by the way, this also applies to ellipticals, exercise bikes, rowing machines, stair climbers, etc.) say for both of them? That they burned the same number of calories.

Since most treadmills only ask you for your age and weight (and the better ones will measure your heart rate, but won\’t take that into account when calculating calories), is there any chance of predicting the number of calories burned that\’s even close to accurate?

The only way to exactly predict how many calories you’re burning is through something called “**direct calorimetry**.”

The way that’s done is you go to a laboratory. They put you inside a special room, and they make you jog or bike or row or whatever form of cardio you can think of, and they measure how much heat you generate.

But there are some flaws with that. First of all, it’s quite expensive. Second of all, it’s very inconvenient, and third, it only tells you about how many calories you burned on that particular workout. Remember that the temperature in the room, what you had to eat, your thoughts, the clothes you’re wearing, and a bunch of other factors affect how many calories you burn. So just because you burned 400 calories in the laboratory doesn’t mean that you’ll burn 400 calories on your own, even though the conditions might seem identical (same speed, same duration, etc.).

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Until next week,

Igor.

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