We asked Tom's Guide readers, 'Which fitness tracking metrics do you trust the least?' Here's the surprising answer

woman running with a cap on — (Image credit: Getty/jacoblund)

We love a poll at Tom's Guide, as it helps us to understand you (our readers) much better, so we can give you more (or less) of what you do (or don't) want.

One poll that recently caught my attention, featured below, asked readers: "Which fitness tracking metrics do you trust the least?" Here's what you said, and why you're definitely on the right track when strapping on one of the best fitness trackers for your workout.

Which fitness tracking metrics do you trust the least?

Here's the results of the top three:

Why calorie burn isn't too accurate on fitness trackers

Calorie burn is very person-specific and varies depending on multiple factors, from lifestyle choices, sex, weight, activity levels, to genetics or health conditions. So before we get into it, if anyone online touts a high-calorie burn workout, I, as a trainer myself, would run a mile.

To test it out myself not long ago, I pressed play on a 500-calorie HIIT workout, and I wasn't even close to the target.

There are several ways to calculate the calories burned during a workout, which I'll briefly summarize below, but your best bet would be to get hooked up in a lab setting, where monitoring would be the gold standard.

Switching up rest-work periods and high-low intensities forces the body to work harder, improves endurance and activates a process called EPOC — Excess Post-Exercise Oxygen Consumption — which means you’ll continue burning calories after exercising. This will help you boost your chances of calorie burn during rest.

Calorie calculators: These use MET value charts to estimate how much energy a person could burn during different workouts, but these are standardized across the board.
Fitness trackers and the best running watches: These track calorie burn by looking at your personal details (age and weight, for example), workout type and factors like heart rate, workout length and oxygen consumption. They’ll estimate VO2 max and expected energy expenditure.
Chest strap heart rate monitors: I'd say these are your best bet for more accurate data. They look at the effort it takes for an individual to do a workout based on heart rate and assess calories you’re likely to burn. Most devices are still only an estimate, though some do better than others based on the wealth of data they have to crunch.

Ideally, you’ll need to find out your basal metabolic rate (BMR) — how many calories your body requires to get through the day — and total daily energy expenditure (TDEE), which refers to how many calories you expend outside of "dedicated" exercise bouts, to help determine likely calorie burn during the day.

There are methods to help you calculate BMR and TDEE, but, as mentioned, visiting a doctor, lab, or sports clinic will help you get more accurate BMR and body mass readings. I'd also recommend measuring your VO2 max and maximum heart rate.

Now, you could go through all of this to find out likely calorie burn, but if you, like me, enjoy training different ways, you're looking at a wide range of calorie burn depending on your activity. And, really, who cares?

Bottom line

I always tell my clients that calorie burn during workouts only determines a very small amount of overall energy expenditure and doesn't really tell you much about your health, fitness, or longevity.

Firstly, your diet moves the needle the most in terms of fat loss or muscle gain. And other areas of your fitness, recovery and health, like Heart Rate Variance (HRV), steps taken, sleep quality, stress, sedentary time and workout intensity, are much more important metrics to look at for your overall health and the likelihood of developing health conditions in the long term.

The best advice I can give is to use calorie burn as an estimate and focus attention on other goals — building strength, increasing muscle mass (which is more metabolically active) and, most importantly, feeling good during and after workouts.

Calorie burn should never really be the focus, so I'm glad to see Tom's Guide readers are wary!

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Sam Hopes is a level 3 qualified trainer, a level 2 Reiki practitioner and fitness editor at Tom's Guide. She is also currently undertaking her Yoga For Athletes training course.

Sam has written for various fitness brands and websites over the years and has experience across brands at Future, such as Live Science, Fit&Well, Coach, and T3.

Having coached at fitness studios like F45 and Virgin Active and taken on both 1:1 and group, Sam now primarily teaches outdoor bootcamps, bodyweight, and kettlebells.

She also coaches mobility and flexibility classes several times a week.

Sam has completed two mixed doubles Hyrox competitions in London and the Netherlands and finished her first doubles attempt in 1:11.