Are you one of those people who obsesses over the calorie counts on everything you buy in the store?  Do you anchor your workouts to the amount of calories your elliptical says you’re burning?

If that’s you, here’s a little bit of advice:  don’t take it too seriously.  At best it’s a crude approximation based on averages.  At worst it misleads you about how much effect you’re having on your body.

And when it comes to exercising, here’s an observation that’s counter intuitive but true: the calories you’re burning don’t mean very much.  Exercise isn’t good for you because it helps you burn more calories.  It’s helpful because it changes the way your body utilizes its energy.

Hell, a wedge of cheese can wipe out your 30 minute treadmill workout.  If that was all there was to it……why even bother at all?

Your body has a variety of physiological states.  After a meal your blood sugar is unusually high and your body’s busy secreting hormones to sweep nutrients out of its system.  Insulin is the chemical it uses to do this.  If you’re in this state too much weird things start to happen, most notably a propensity to store FAT.

Various types of exercise can turn this process off, most effectively when you achieve a high heart rate, regardless of how many calories you burn.  A high heart rate depletes your glycogen (sugar) stores in your muscles, which increases the need for insulin receptors on your muscles, which is helpful because that allows you to start burning glucose off as energy instead of storing it as fat.

How Your Treamill Counts Calories, How Your Body Counts Calories

Your treadmill uses an algorithm that’s based off of averages.   However, your body doesn’t go off averages. It usually follows a power law.  That means the most important changes are often concentrated in a small number of moments.  (Like when you’re lying on the floor after a hard workout).

How your body actually burns calories is due to a combination of how much oxygen you’re consuming and carbon dioxide you’re producing.  (It’s called the weir equation).  The particular number lies at an intersection of your weight, body fat %, age, heart rate, and even the sorts of food you ate that day and small deviations in these categories can sum up to large differences that are remarkably unique to the individual.

When it comes to measuring your physiology, the machine is quite dumb.  You could say it’s constantly applying the laws of physics to the field of biology.

Less Calories, More Results

I just finished reading an interesting paper that compared the effects of exercise on two groups of people.  The first group started exercising at moderate intensity for four weeks.  The second group exercised for the same amount of time but did high intensity intervals instead.

The moderate exercisers burned twice as many calories.  The interval exercisers burned nine times as much fat.

Why?

The biggest difference between the two groups is the interval exercisers were producing more enzymes that helped clear glucose out of muscle cells.

Your body stores glucose in two places: the muscle and the liver.  They do this for very different reasons.  The glucose in your liver is there to help maintain a steady blood sugar level, because your brain needs a constant influx of sugar in order to function.

Your muscles store glucose for rapid energy expenditure.  It’s the reserve your body keeps around to fuel its fight or flight response, and this effect is designed to cascade.  This makes perfect evolutionary sense.  If a bison starts chasing you you’re only going to survive if you can mobilize your energy stores very quickly.  It’s a well conserved feature in the animal kingdom.

But when the glycogen is depleted from your muscle cells there’s an increased need for insulin receptors on muscle cell surfaces afterwards to top them back up with glycogen.  This allows your body to clear sugar out of its system more efficiently, and allows it to burn fat instead of sugar after your workout.

The Key Point About Exercise

If there’s a take home point to all this, it’s that the benefits of exercise occur after you workout, not while you workout.  That’s when the most important work is done, as your body re-calculates how it needs to partition its energy sources.

And it’s not gospel that high intensity exercise is the end-all be-all to good health.  In fact, it’s probably best to blend it with regular leisure activity like walks and hikes in order to get the best results.  And plenty of sleep.

But you don’t have to obsess over your calories every time you walk into the gym or eat a meal.