You’re Not Burning as Many Calories as You Think

Most of us overestimate how much energy we burn on the bike. Here’s how to get a more accurate number. – By Selene Yeager

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Most people overestimate their calorie burn—often by a lot. (Like enough to overlook an extra everything bagel.) But it’s not your fault.If anything, health writers like me deserve to shoulder a large chunk of the blame. For years we touted the amazing calorie-torching benefits of everyday levels of activity, like, say, a leisurely coffee shop ride. We didn’t mean to delude anyone; we were being deluded ourselves, relying on tools like calorie calculators that estimate energy expenditure using formulas based on METs (short for metabolic equivalent of task) and weight. And those numbers can be highly individual—or woefully inaccurate.

For instance, let’s take that leisurely ride. Generally, cycling about 20km/h comes in at 8 METs, which means a 68kg rider may burn more than 540 calories in an hour. That’s a strong “may,” though—especially if that rider is also pretty fit on the bike. Because the fitter you are, the more efficient you are, and (file under “life’s not fair”) the less energy/fewer calories you use when you ride at a given intensity. That figure also never takes into account the fact that you’d be expending 1 MET and burning 68 calories that hour even if you were doing nothing more strenuous than watching Game of Thrones.

So if you reward your 540-calorie ride with a chocolate scone and large latte, your weight may trend in a direction opposite of what you’re aiming for.

RELATED: 14 Ways to Lose Weight With Your Bike

But everything is better that we have electronic wearables tracking our every step and shimmy, right? Yeah. About that.

A Stanford study published earlier this year reported that not one of the seven devices they tested—including the Apple Watch, Fitbit Surge, Mio Alpha 2, Basis Peak, Microsoft Band, PulseOn, and the Samsung Gear S2—delivered an accurate number for energy expenditure. The most accurate one was off by 27 percent. The least accurate one? Ninety-three per cent. And six of the seven devices measured heart rate accurately to within five per cent. As lead researcher Dr. Euan Ashley, professor of cardiovascular medicine, genetics and biomedical data science, told the Stanford Medical News Center, “Basing the number of doughnuts you eat on how many calories the device says you’ve burned is a really bad idea.”

GarminConnect, Strava, and other training apps might be a bit better, but they’re not perfect, either, and the number they give you depends heavily on the information you give them. The more detailed data you input about yourself, such as age, height, weight, gender, and max heart rate, the more accurately their internal algorithms can calculate your calorie burn. Wearing a heart rate monitor that is synced to your device also helps make your calorie count more accurate.

Ultimately, however, the best way to know how much energy you’re burning as you rip down the road is by using a power meter. Power meters measure the work you’re performing and display it in kilojoules, which is a unit of work that takes into account that the human body isn’t 100-per cent efficient when turning energy from your fuel stores into physical work, like pedaling a bike.

“Kilojoules and calories burned in cycling convert to a 1:1 ratio,” says USA Cycling level 1 elite coach Daniel Matheny, head coach at Matheny Endurance in Colorado Springs. If your ride file says you performed 800 kJ of work, you can feel confident within a five per cent margin of error, that you burned 800 calories.

Still, it’s extremely important to remember that even if you get the most accurate calorie data possible, there’s more to fitness and weight loss than that number. High-intensity interval workouts, for example, deliver a huge training effect by increasing your maximum oxygen consumption (VO2 max), raising your lactate threshold, and improving your economy, all of which allow you to stay “aerobic” longer, so you can burn more fat at higher intensities. But they don’t ultimately burn an impressive number of calories while you’re doing them.

RELATED: 4 Great Time-Saving Workouts

Even more importantly: If it’s weight loss you’re after, you’re better off becoming more mindful of the calories you consume—looking most closely at the quality while keeping an eye on the quantity—than those you burn. Research has clearly demonstrated that you can lose weight relatively easily without exercising, but it’s far harder to shed pounds without a healthy diet.

So keep riding, and include a couple of hard outings with hills or intervals every week. And feed yourself a high-quality diet rich in whole, unprocessed foods. For guidance, a recent landmark study of more than 135,000 people across five continents found that a diet that avoids excessive carbs (more than 60 per cent of your daily intake) and includes about 35 per cent of fat, as well as three to four servings of fruits, veggies, and legumes a day is your best bet for good health.

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