Most people overestimate their calorie burn - often by a lot. 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 18km/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.

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 per cent. The least accurate one? 93 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.”