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You probably have an activity tracker. A FitBit, a smartwatch, or an app that tracks SOMETHING about your activity.
After a tough workout, you glance at how many calories you burned and wonder if you'll have room for some dessert tonight. I mean, you could fill a kiddie pool with all your sweat. That's got to mean something, right?
But before you start budgeting for your ice cream, you should know the truth about the estimated calories burned from these trackers.
They're wrong.
Way wrong.
Sorry to be the harbinger of bad news.
There are two main problems with trackers:
The "Net Calories Paradox" (calories earned)
Trackers grossly over-estimate caloric expenditure
1) Net Calorie Problem
The first problem is what I call the "Net Calorie Problem" or the "I've earned it" mentality. If you've done your research, you know that creating a calorie budget and staying within that budget is the only way to lose weight.
People usually eat more than they think, anyway. So it's extra important to stick to the calorie budget. But sometimes exercise makes you hungry. And in a moment of weakness and a very convincing argument from the Freudian Id, you convince yourself that "you've earned it." Especially if your tracker reports a 450 calorie burn after a 45 minute workout.
After some quick napkin math, it's off to the frozen treats for a well-deserved reward.
But the whole point of the exercise was to create a calorie deficit. There's no good reason to eat back calories.
The popular calorie-tracking app MyFitnessPal is a big perpetrator of this mentality. It syncs with most trackers and then suggests that you have "extra" calories in your budget after a workout. It calls this the "Net Calorie Equation".
Unfortunately, the original calorie estimation was already including regular exercise! No need to eat it back.
This is like budgeting for a vacation with the bonus you're going to get next month, then spending that bonus on a new car. Whoops, it's gone! No vacation.
I don't know why MyFitnessPal does this. Maybe someone can enlighten me.
2) The Trackers Are Just Plain Wrong
There's a popular research study from 2016 that's made the rounds through the fitness community. It found that trackers OVER-ESTIMATED the energy expenditure by 16-40% when doing cardio activities.
Another 2017 study from Stanford looked into the accuracy of wrist-worn devices like FitBit and Apple Watch. These devices measured heart rate correctly - which is fine - but were off on energy expenditure by up to 93%!
I mean,with an inaccuracy rating of 93%, why even try?
This is a pretty big margin of error.
An error rate of that size is the difference between 300-500 calories. If you add that up per workout, throughout the week, that could be several thousands of calories per week you're over-eating.
So What To Do?
Don't go throwing your trackers in the trash just yet. Even though the calorie count may not seem accurate, they still have other purposes. Here are some benefits of using a tracker:
They track heart rate accurately (especially on the torso).
They can track movement, location, and overall activity pretty well.
They can estimate your overall intensity.
They are consistent with themselves.
That last one is important. Even though a tracker may inaccurately report a burn of 600 calories, it should theoretically report the same burn during a repeat exercise. That means you can compare workouts, even if the actual number is wrong.
If Monday's workout "burns" 600 calories, but Thursday's workout "burns" 1000, you'll know Thursday was more effective.
Some points of Reference:
If really want to know how many calories you burn (it's not an exact science), you can always estimate.
Travelling 1 mile will burn about 80-150 calories. The bigger you are, the more the burn. Running might be slightly higher than walking, but not by much.
One hour of vigorous resistance training (weight lifting) will burn about 200-300 calories, depending on how much rest you're taking, number of reps, and overall intensity.
The more you exercise, the less calories your body burns.
Take another look at that last bullet point.
If you're exercising regularly, you get good at exercise. This means you'll burn less calories during exercise. As you get leaner, your body burns less calories. There's a decreasing rate of return on exercise and calories burned.
So the take-home message:
Don't eat extra calories because you worked out. You didn't burn as much as you think - no matter what your watch tells you.
MORE Information
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