February 13, 2020

How many calories did you really burn?

If you’ve used a treadmill or stationary bike at the gym, you’ve likely seen the amount of calories you’ve burned displayed on the screen when your exercise is done. Or, if you have a fitness tracker, you might be tracking the calories you’ve burned throughout the day. But are those numbers accurate?

According to UW Health senior exercise physiologist with the Fitness Center Jude Sullivan, the answer is, “it depends.”

We all know that a calorie is a measure of energy, and that our bodies are constantly burning calories – or exerting energy. The more you do, the more calories you burn. But people don’t burn calories at the same rate. Age, gender and weight all influence how fast you burn calories.

When it comes to gym equipment, the calculations used by the machine are based on the average population. To simplify it – the machine has been told that a 5’5” woman is expected to burn X amount of calories for every 1 minute of pedaling on the bike. Other variables such as speed and resistance are factored in as well. And that is unique to every piece of equipment – treadmill use burns calories differently than elliptical, which is different still than a stationary bike.

What the machines aren’t able to account for is how you use them.

“People can 'help themselves' during the activity,” notes Sullivan. “Leaning on the side rails of a treadmill, for example, will affect the amount of calories a body uses.”

He goes on to note that the temperature, humidity, terrain and fitness level are a few of the other variables that may be a factor.

As for wearable fitness trackers, the same is true. Depending on the device you may be asked to add a few additional pieces of information – like the temperature or what the activity is. Some devices may even have a GPS tracker that can account for the terrain that you’re on, like hills. But given the unique nature of every device and piece of equipment, you may find that your tracker reports a different amount of calories burned from the treadmill you might be using.

“I would recommend comparing the tracking device to the stationary equipment,” suggests Sullivan, who explains that doing so can give you a sense of the differences between the two. But he is also quick to point out that too much information isn’t necessarily a good thing.

“Some apps keep track of a lot of different data points,” he says. “But you have to be cautious. It can be challenging to interpret what the information is telling you over the course of time.”

And for those who may eschew devices altogether in favor of judging a workout by how tired you are afterwards — unfortunately sweat and fatigue aren’t a great measurement of exertion.

“There’s a sense that if a workout is exhausting, then you must be burning a large number of calories,” comments Sullivan. “But that may not be a consistently good measurement of exertion. And, the reality is that if one is always working out at that level, it will be difficult sustaining it over an extended period of time so the calorie burn may not be as significant as you perceive.”