The Danger Of Overestimating The Calories You Burn

When you’re trying to lose weight, a big part of it is figuring out how to maintain the right energy deficit.

As I’ve discussed before, the amount of weight you will lose is determined by your energy balance.

This means if the amount of energy you take in is less than the amount you burn, you will lose weight.

Sounds pretty straightforward so far, right?

Well, in theory it is, but in real life it is not always so simple…

In fact, one of the biggest issues that I find many guys running into here is accuracy.

That is, in order for all of this to work, you have to be able to accurately gauge the amount of energy that you’re taking in, as well as the amount of energy you’re burning – otherwise, the entire thing falls apart.

In this article, I’m going to cover one of the areas where this tends to go wrong, so that you can hopefully save yourself a lot of frustration.

The ‘Energy In’ Part

When I talk about ‘energy in’ here, what I’m really referring to is the number of calories that you’re eating each day.

Calories are simply a form of stored energy, and are really the only way that you take energy into your body.

In this respect, it makes this part of things a lot easier to figure out.

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You can log what you eat in a food tracker like FatSecret or MyFitnessPal, and have a pretty good sense of how many calories you’re eating each day – and, by extension, how much energy you’re taking into your body.

Now I’m not saying that maintaining a diet is easy here – far from it – but what I am saying is that from a tracking standpoint, you can estimate this part of the energy equation fairly accurately.

The ‘Energy Out’ Part

Now let’s take a look at the other side of the equation – the ‘energy out’ part.

This is where things get a bit more tricky…

You see, unlike the ‘energy in’ part, where you can get a fairly accurate sense of things by tracking your food intake, the ‘energy out’ part has more factors to take into consideration.

First of all, your basel metabolic rate (known as your BMR, for short) makes up a major percentage of the total amount of energy your body burns each day.

This can vary significantly from person to person, and can be tough to quantify accurately.

After that, you have to take various other factors into consideration, such as the thermic cost of food, how much you’re exercising, and even how much you’re randomly moving around during the day (known as NEAT).

As a result, it is pretty tough to know how much energy you’re actually burning each day.

But without this vital piece of information, how are you supposed to know how many calories you should be eating in the first place?

Where Many Guys Go Wrong

As you might expect, there are many methods to determine how many calories you’re burning each day.

Unfortunately, many of these methods aren’t very accurate at all, and end up drastically overestimating your caloric expenditure.

One increasingly popular method is using a fitness tracker – like a FitBit or Misfit – to gauge how many calories you’re burning each day.

And while this seems good in theory, in my experience working with clients these trackers tend to significantly exaggerate expenditure.

This is because fitness trackers estimate calories based on the number of steps you’re taking each day, and then use an algorithm to determine how many calories you’ve burned based on that.

But as we’ve already discussed, with all of the factors that go into accurately figuring out how many calories your body is actually burning each day, these estimates are rarely on the mark.

What tends to happen, though, is that people who get into the whole fitness tracking thing start taking these caloric estimates far too literally.

That is, if their tracker told them that they burned 2800 calories that day, then they feel that eating anything under 2800 calories will cause them to lose weight.

And, in turn, they’ll be surprised (and unhappy) if they do that and don’t lose the expected amount of weight.

But this is the wrong way to go about it…

A Better Way to Estimate Your Calories

Instead of basing your caloric intake around the number that a fitness tracker gives you, I find that a better approach is to calculate your estimated energy expenditure yourself.

To do this, you first need to figure out your BMR, which I show you how to do in this article.

This varies considerably from person to person, but the specific calculator that I recommend using in the article tends to be reasonably accurate.

After that, you’ll want to calculate your TDEE, which stands for Total Daily Energy Expenditure.

Your TDEE will serve as a good basis for you to determine how many calories you should be eating each day.

If you’re planning on losing weight, I would recommend eating at 75-80% of your TDEE.

However, the most important thing to remember here is that your TDEE is still just an estimate of your energy expenditure each day.

A good estimate, but still just an estimate…

This means that you should view that number as a starting point, which you may need to adjust based on whether or not you’re losing the appropriate amount of weight each week when you weigh yourself.

But whatever you do, don’t treat ANY of these calculations as being absolute truths.

And if you do use a fitness tracker to gauge how many calories you’re burning, it is most useful to treat it as a relative measure – how much activity you did in a given day, compared to previous days.

That way, you’ll save yourself a lot of frustration, and be much less likely to fall into the common trap of overestimating the calories you burn each day.

Are you having trouble figuring out how many calories you’re burning daily? Let us know in the comments below.

3 Reasons You May Be Burning Fewer Calories Than You Think

How many calories are you burning each day? If your weight loss has stalled, you’re probably burning fewer calories than you think. Common mistakes, such as eating hidden sugars and sitting for long hours, can hamper your progress. Calorie counters are rarely accurate, so don’t rely on them.
The truth is that most people overestimate the number of calories burned. At the same time, they underestimate the calories consumed. This can lead to plateaus and frustration. Fortunately, it’s never too late to get back on track.
Here is why you may be burning fewer calories than you think:
Your Fitness Tracker Might Be Lying
Research shows that most fitness trackers are getting readings wrong by a whopping 40 percent. This goes for trusted brands like Jawbone and Fitbit. The fitness trackers on gym machines are even worse.
Other studies have found a degree of inaccuracy ranging from 20 percent to 93 percent. The elliptical trainer appears to be the least accurate when it comes to tracking calories.
The whole point is that you can not trust fitness trackers. For instance, let’s say the treadmill shows you’ve burned 550 calories. In this case, you’d say: “I’ve had enough exercise for today, now I can eat more.” So you go home and have a big meal.
Seek other ways to track your progress. Take before and after photos, measure your waist and thighs, or use skin calipers. Fitness trackers are not an indicator of how hard you’re working toward your goals.
You’re Getting Fitter
As you lose weight and get fitter, your body begins to burn fewer calories. According to science, fit people have a lower energy expenditure during exercise. This explains why you lose weight faster when you’re just starting a workout program.
Keep your training varied to burn more calories. Change workout variables, such as the number of reps and sets, intensity, and duration.
Tweak your eating habits and load up on protein. This will boost your metabolism and increase fat burning. Drink CLICK before or after exercise to get more protein into your diet.
You’re Overestimating Your Calorie Burn
Not all exercises are created equal. Some increase muscle size and strength, while others work better for weight loss. On top of that, the number of calories burned during exercise varies from one person to another. Thus, it’s easy to get confused and overestimate your calorie burn.
Most people burn 250 to 300 calories per hour when lifting weights. Steady state cardio burns anywhere from 300 to 600 calories per hour. Tabata and high-intensity interval training (HIIT) can burn about 500 calories in 30 minutes.
As you see, exercise doesn’t torch a ton of calories. Just because you’re working out, it doesn’t mean you can eat a whole pizza later in the day. Be realistic and watch your diet. Not even the best training program can compensate for bad eating.
These are just a few of the reasons why you’re burning fewer calories than you think. Consider your age, weight, fitness level, body composition, and resting metabolic rate. All of these factors impact your calorie expenditure. If your goal is to slim down, clean up your diet. What you eat accounts for over 80 percent of your results.

Your fitness tracker is probably overestimating the calories you’re burning

You’re off to the gym, what do you take with you? Workout gear, check, water bottle check, fitness tracker, double check.

Unfortunately, a new study by a team at Aberystwyth University has found that popular brands of fitness trackers are overestimating the number of calories burned by more than 50 per cent.

The researchers found that the trackers were inaccurate during walking and running tests. Dr Rhys Thatcher, who conducted the study, said the devices had an “inherent tendency” to over-measure.

Fitness trackers: not so good at tracking

Dr Thatcher worked with the BBC X-Ray programme to test the trackers. Using a group of volunteers, the study measured the amount of oxygen a volunteer used during 10-minute walking and running sessions on a treadmill, before comparing it to the stats supplied by the various trackers.

In general, the accuracy of the trackers varied when measuring running or walking.

The Fitbit Charge 2, priced at £139.99 and is one of the most popular fitness trackers, only underestimated calories burned when running by 4 per cent. However, when measuring walking, it overestimated by more than 50 per cent.

The Letscom HR band, which retails at £20, underestimated the number of calories burned when running by 33 per cent and overestimated calories burned when running by 15.7 per cent.

Alternatively, the Letsfit, also £20, underestimated the number of calories burned when running by 40 per cent and, while it did overestimate calories burned during walking, it was only by 2 per cent.

Speaking about the results, Dr Thatcher, told the BBC: “If you want to know the exact number of calories that you are burning during an exercise session then it doesn’t matter which device you use, you have to interpret the data with some caution.”

The Fitbit Charge 2 (pictured here) underestimated calories burned during running, but overestimated them during walking (Fitbit)

It’s not so surprising that fitness trackers aren’t the be all and end all when it comes to monitoring how many calories you’re burning, as a lot of the time the companies themselves say the information they offer is only based on estimations. This is one of the reasons Google overhauled its Google Fit app last year, to move away from arbitrary health goals such as 10,000 steps.

The app was redesigned to encourage users to carry out activities such as a brisk walk, run or exercise class in order to earn Move Minutes points for each activity. It also included a Heart Points tracker, to encourage people to do activities that get their heart pumping.

At the time, Google said: “When it comes to your health, it’s important to move more and sit less. Earn Move Minutes for all of your activity and get motivated to make small, healthy changes throughout your day, like taking the stairs instead of the elevator, or catching up with a friend over a walk instead of a coffee.

“Activities that get your heart pumping harder result in even greater health benefits.”

If you’re looking for ways to improve your fitness in 2019, here are the best free fitness apps to try.

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Nike and Apple have agreed to a $2.4 million settlement over claims the Nike+ FuelBand failed to accurately track calories burned by the fitness tracker’s users.

The settlement comes as Nike and Apple have moved on to other projects—Nike has mostly shuttered its digital products division and Apple has bet big on its own Apple watch, which comes with an array of health and fitness features.

But the lawsuit shines a light on the growing market for wearable technology, which claim to count everything from calories to when a woman had her last period. And it reminds us that a lot of claims from consumer-facing health products may not be rooted in science, but in marketing.

Los Angeles resident Carolyn Levin sued the companies in California in 2013, claiming FuelBand users ”experience wildly inaccurate calorie burn readings” and that people who purchased the fitness band were misled. She alleges that Nike and Apple knowingly engaged in false and misleading advertising for the fitness band, which the companies launched in 2012 to much fanfare.

Nike and Apple continue to deny the allegations. They said they wanted to settle the case in order to avoid future legal costs. Nike will give people who bought the gadget $15 in cash or a $25 Nike gift card in exchange for giving up rights to bring future legal action.

My life with the Nike FuelBand activity tracker

Nike FuelBand Nike

As covered in my introduction, I’ve been living with four different activity trackers as part of an ongoing test. It’s time for a close-up of how one of them works: the Nike FuelBand. The tracker has managed to be both my favorite and least favorite of the devices.

The FuelBand is a simple, lightweight device (about 1 oz.) that you wear around your wrist. I found it fairly comfortable, quickly forgetting I had it on, even when typing.

The band costs $150 and is available in three slightly adjustable sizes. Data can be synced via a desktop app (for PC and Mac) or via iOS devices; there is no Android app yet. The band charges quickly by plugging directly into a USB port. No cable or special adapter is required, which is nice.

Activity on easy display

The Nike FuelBand is the only one of the four devices I’m using that has a display I can consult right on my wrist. The Jawbone Up and BodyMedia Fit both lack displays, and to see the display on My Fitbit One, I have to unclip it from my waist. With the Nike Fuelband, I simply push a button and immediately I can see one of four things:

  • Time
  • Steps
  • Calories
  • Fuel

The NikeFuel Band will count your steps, as will the other trackers. But, more importantly, it calculates how much “NikeFuel” you’ve generated on a particular day.

NikeFuel, rather than steps or calories

What’s NikeFuel? Think of it as Nike’s attempt to fairly measure activity levels in a way that counting steps or calories can’t measure. Counting steps to measure activity gets derailed when people are doing non-step activities, like stand-up paddleboarding. As for counting calories, a large man will burn more calories than a small woman — even if they are doing the same level of activity — by virtue of the fact that the man is larger and thus expending more calories. NikeFuel strives to measure the activity levels of both these individuals fairly when compared to one another. As Nike’s site explains:

Unlike calorie counts, which vary based on someone’s gender and body type, NikeFuel is a normalized score that awards all participants equal scoring for the same activity regardless of their physical makeup.

How might you compare your activity level to someone else? That’s where the Nike FuelBand app comes in, allowing you to connect with other FuelBand users who have Facebook, Twitter, or Path accounts. (If you use the Web site rather than the app, only connecting to Facebook users is an option).

Comparing NikeFuel socially

Connect to NikeFuel and any friends you have on one of these services who also have connected their FuelBands will appear in the “Friends” area. You’ll see their Fuel levels, and they’ll see yours: Friends displayed in Nike FuelBand app (pictures and names changed, but general appearance is the same)

There’s no pick-and-choose option. If you’re concerned about a particular friend seeing your activity, don’t connect. Otherwise, you’ll have to unfriend them to keep your activity private.

The idea behind seeing what your friends are doing is supposed to be a motivating factor. For some, if they have close friends actively using Nike FuelBands, this might work. But for me, I preferred the much more social aspect that the Jawbone Up band provides, where you see more of what people are doing (if they share) and can comment on it. I’ll be covering more about the Jawbone Up in a future column.

NikeFuel as personally motivating

Where NikeFuel really worked for me was as a personal motivation tool. At any point during the day, I can push the button on the band to see where I am in relation to my goal: Nike FuelBand showing “Fuel” earned. Colored dots at bottom also show progress to daily goal, going from red to yellow to green as you get closer.

After using the Nike FuelBand for a few days, it was clear that I was hitting a Fuel level of 2,200 on a regular basis. So, I started stepping it up, first to 2,300 and then to 2,400. Getting to that 2,400 level each day became a real effort, one that required me to ensure I was doing extra activity to reach it.

And boy, did I find myself working for it. In the past after a hard day of work, I might have decided to skip going out for some inline skating or paddleboarding — activities I often try to do at the end of the day. With the FuelBand showing my daily progress — or lack of progress — I found renewed energy to get out each evening.

That pressure built as I met my goal each day. My “streak” began to grow, and I didn’t want to break it.

The screen above is one of the many different ways the app congratulates you and reinforces you on your activity. The little character is called “Fuelie,” and it dances around when you gain an award or milestone. It’s kind of fun when it happens. The app has an area that also consolidates all your achievements.

None of my other devices motivated me this well, which is why the Nike FuelBand is my favorite. But it’s also my least favorite because, more than the others, it can fail to reward me for some of the exercises I do.

What Nike FuelBand misses

There are a number of exercises the Nike FuelBand won’t capture or doesn’t capture well. Nike itself even talks about some of the activities that it’s not suited for, such as weightlifting or yoga.

Both the Fitbit and Jawbone Up have similar issues. The difference is that you can manually enter exercises with both of those, so the missed activity still gets added to your overall tracking. The Nike FuelBand has no such option. That’s a huge oversight.

For example, one night I was just short of my NikeFuel goal for the day. I did 20 pushups to try and reach it, but earned nothing. My wrist doesn’t move doing pushups, so no Fuel accumulated. Then I brushed my teeth, which generated 19 Fuel points. Crazy.

In another example, I don’t generate a lot of “steps” to measure when I’m inline skating — nor does my wrist move much because I tend to skate with my wrists resting on the small of my back. Because my hips move, however, my Fitbit on my waist ended up measuring more calories burned than my Nike FuelBand.

Of course, as mentioned, with stand-up paddleboard, the Fitbit has issues that the Nike FuelBand doesn’t. I don’t step, so the Fitbit has little to measure. The Nike FuelBand, in contrast, can measure that my arm is moving from the paddling because it’s on my wrist. But with the Fitbit, I can make up for its deficiencies with manual logging. With the FuelBand, you’re stuck.

Quick look: estimating calories

A related issue is how well the Nike FuelBand tracks the activities it’s supposed to track. Even though it’s not focused on calories, the Fuel level is based off of them — plus you might just want to know. So, does it estimate calories correctly?

My best guess at this is to compare the FuelBand to the BodyMedia Fit, the latter of which uses skin sensors to estimate how active I am. As with the Fitbit and Jawbone Up, the Nike FuelBand was always registering lower than the BodyMedia Fit. Depending on the activity, results varied on whether it beat Fitbit and Jawbone Up.

I’ll revisit this more in the conclusion to my series on activity bands, but here’s a quick comparison on two activities to date. First, stand-up paddleboard:

The lines show calories burned on four different occasions that I went paddleboarding. The time varied, which is why sometimes more calories were burned. The important thing is the gap between the lines. If they all measured the activity the same, there would be little gap. That’s not the case.

The BM line shows calories burned as estimated by the BodyMedia Fit. It always registers more than the other bands, and, as I said previously, it is probably the closest reading to what I actually burned. The Nike FuelBand consistently registered about half of what the BodyMedia device did. The Fitbit and Jawbone Up registered much less.

Now consider inline skating:

The chart shows three occasions when I went inline skating, each for different lengths of time. Again, the BodyMedia registered the most. But this time, it was the Fitbit that seemed to more accurately track calories burned in this activity over the Nike FuelBand and the Jawbone Up.

Somewhat related, it’s disappointing that there’s no way to zoom in and see the amount of calories burned during a set period of time. Consider a recent daily chart:

On this day, I went inline skating and paddleboarding and for a bike ride. That’s what those three spikes represent. But I can’t select a time period to see what calories were estimated to be burned during these periods, as you can with the BodyMedia. Nor is there any timer you can set — which is possible with Jawbone Up — that calculates estimates for a particular activity.

Good motivation tool, pity not more refined

Again, I’ll revisit how accurate each device seems to track activity in the conclusion to my series. But as I said in the introduction, I’m not focused on whether a band perfectly tracks all my calories burned throughout the day. To me, the real goal of all of these is whether they help you know if you’re keeping activity relative to previous days — and encouraging you to be active, if you’re not.

The Nike FuelBand does that well, providing better immediate feedback than the other devices, thanks to its display. It’s a real pleasure to see it light up with “Goal” when you’ve made it.

It’s a shame you can’t manually add activities, which would correct the biggest flaw with the FuelBand, in my opinion. Other issues are that the app has no food-tracking option, which my other three trackers do provide. Those trackers also provide sleep tracking, which I find to be more of a novelty than anything else. However, for those who want it, Nike not having it would be a drawback.

If most of your activity is walking or running and if you like some of the other Nike+ products , such as how the FuelBand can work with an iPod Nano integration, then this might be a more compelling purchase.

As for my other bands, stay tuned. I’ll post my experiences with each of them over the coming weeks, and each will be posted to the home page for this series, making it easy to watch for them.

Also be sure to see CNET’s formal review of the product plus the video review, below:

Now playing: Watch this: Nike FuelBand 2:48

Fitness trackers’ accuracy varies widely for calories burned

(Reuters Health) – Even though many people swear by fitness trackers to help lose weight and stay in shape, a review of existing research confirms that many of these gadgets are not very good at measuring how much energy we burn.

For the analysis, researchers examined data from 60 previously published studies that tested the accuracy of energy expenditure measurements for 40 different devices worn on the arm or wrist. Accuracy varied widely, but it was a bit better when devices factored in other measurements like heart rate to calculate calories burned.

“Our paper shows that estimates are often poor and they vary depending on the activity being performed,” said lead study author Ruairi O’Driscoll of the University of Leeds in the U.K.

“Consumers should be aware of the potential for error in their devices, especially if they are using it to inform their eating behaviors,” O’Driscoll said by email.

When fitness trackers overestimate exercise, people who need more exercise to maintain or lose weight might get too little activity, increasing their risk for obesity and other chronic health problems, the researchers note in the British Journal of Sports Medicine. At the same time, trackers that underestimate activity might lead some people to overdo it and put too much stress on their cardiovascular system.

All of the studies in the analysis looked at energy expenditure in different ways, and with different types of exercise and activities. They often compared fitness trackers to proven methods of monitoring energy expenditure that are typically used only for research, like locking people in a room to assess every calorie consumed and burned or asking people at home to drink specially treated water that makes it possible to detect energy output with a urine test.

Taken as a group, the consumer devices tended to slightly underestimate energy expenditure, the researchers found. The devices with the biggest underestimations of energy burned, according to the results, were: Garmin Vivofit, Jawbone UP24 and SenseWear Armband Pro3.

At first glance, other fitness trackers got measurements more similar to those from proven methods of assessing energy expenditures: Apple Watch, Bodymedia CORE armband, Fitbit Charge HR, Fitbit Flex, Jawbone UP, Nike FuelBand, SenseWear Armband, and SenseWear Armband Mini.

But in many cases, there wasn’t enough data to rule out the possibility that results were random or due to chance.

Devices tended to be more accurate at measuring energy expenditure when they also monitored heart rate or body heat, but this was not consistent across all types of activities.

Accuracy also depended on the activity. Fitness trackers often did a poor job of measuring less vigorous movement like walking, climbing stairs, and doing household tasks.

Participants in the studies were 35 years old on average and typically not overweight. Results might be different for older people or obese individuals, the study authors note.

“Most research has shown that wearable devices and activity monitors are not that accurate for measuring energy expenditure,” said Dr. Mitesh Patel, director of the Penn Medicine Nudge Unit at the University of Pennsylvania in Philadelphia.

“For most people, energy expenditure estimates from wearable devices should be used as a gauge (e.g. high or low) as the numbers may not be accurate but trends higher or lower may be more likely to be correct,” Patel, who wasn’t involved in the study, said by email. “Other measures like step counts may be a more accurate and better indicator of how much activity a person has done.”

Fitness trackers with heart rate monitors might be more accurate because the added data helps assess how hard people are working during exercise, said Lisa Cadmus-Bertram, a researcher at the University of Wisconsin-Madison who wasn’t involved in the study.

“There are several trackers under $150 that do include heart rate technology, so you don’t need to get a top-of-the-line tracker,” Cadmus-Bertram said by email.

“Overall, consumers do need to recognize that the technology isn’t perfect and that trackers are providing estimates; it’s not a magic number that reflects the exact number of calories burned.”

SOURCE: British Journal of Sports Medicine, online September 7, 2018.

Our Standards:The Thomson Reuters Trust Principles.

Fitbits and other trackers are overestimating the number of calories burnt during walking, scientists have said.

Tests at Aberystwyth University found some of the products were inaccurate by more than 50 per cent.

The experiments measured the amount of oxygen a volunteer used during ten-minute walking and running sessions on a treadmill, comparing the data to the a number of trackers.

The researchers found that the best-selling Fitbit Charge 2, which costs around £80, was fairly accurate in estimating the calories burned while running, underestimating by only four per cent.

However, the device underestimated the calories burned during walking by more than 50 per cent.

Other less expensive devices, such as the Letscom HR and the Letsfit, were more accurate during the walking test, overestimating calorie burn by 15 per cent and two per cent respectively.

But they underestimated the total during running by 33 and 40 per cent.

Dr Thatcher said: “If you want to know the exact number of calories that you are burning during an exercise session then it doesn’t matter which device you use, you have to interpret the data with some caution.”

The research follows warnings that fitness trackers inaccurately estimate the amount of weight lost following exercise, particularly for overweight people.

This Fitbit model had the most accurate calories burned calculation, in a study that compared it to other similar devices

  • One study found that the Fitbit Surge had the most accurate calories burned calculation among a group of similar devices, with an error rate just over 25%.
  • The other similar devices tested had comparatively higher error rates – up to as much as 93%.
  • Still, Fitbits and similar devices are all making an estimate based on your health and activity rate, and their accuracy can vary greatly.
  • Visit Business Insider’s homepage for more stories.

Fitbits use an algorithm that processes a wealth of data in calculating your calories burned, including information gleaned from your daily activities and about your general health.

But how accurate is a Fitbit’s calorie burn calculation?

Check out the products mentioned in this article:

Fitbit Surge (For $209.95 at Amazon)

Measuring the accuracy of calories burned on a Fitbit

A 2017 study published in the Journal of Personalized Medicine found that Fitbit Surge model had about a 27% margin of error, the lowest margin of error among the seven devices tested.

Other similar devices in the study — including the Apple Watch, PulseOn, and Samsung Gear S2 Basis Peak, Microsoft Band, and Mio Alpha 2 — had higher error rates, up to as high as 93%, rendering them more inaccurate when it comes to calculating calories burned.

Essentially, Fitbits calculate calories burned by making an educated guess based on several known factors.

The first is your Basal Metabolic Rate (or BMR) – the rate at which you burn calories at rest to maintain vital body functions – which Fitbit estimates based on your age, gender, height, and weight. Herein lies one problem with the measurement, as not everyone of the same age, height, and weight is going to be at the same fitness level, have the same metabolism, and so on. Already the Fitbit is using generalizations when it runs its calorie burning algorithms

With this baseline data, the Fitbit then uses the activities in which it records you engaging, factoring in your heart rate and motion, as well as activities you manually enter into your profile. All of these data together with your BMR serve to create the estimate of your daily calories burned.

Given all the areas for potential error – including tweaked data input by users and variation in Fitbit models – the accuracy of the calories burned calculation will surely vary.

But at the very least, your Fitbit can still be used as a helpful guideline for planning fitness and weight loss goals.

Related coverage from How To Do Everything: Tech:

  • How a Fitbit is able to accurately track your movement, and how to check your step count on it

  • Here’s how long it takes a Fitbit to charge, and how long its charge should last

  • How to update your Apple Watch and get the device’s latest features

  • How to tell if your Apple Watch is waterproof or water-resistant, and to what extent

Researchers at Aberystwyth University have claimed some fitness trackers have an “inherent tendency” to overestimate the number of calories burned while walking by more than 50 per cent, according to BBC X-Ray.

The researchers’ tests are said to have measured the amount of oxygen used by a volunteer with an oxygen monitor during ten minute walking and running sessions on a treadmill, after which the data was compared to various fitness trackers.

These included the Fitbit Charge 2, Letscom HR and Letsfit according to the BBC report, so “various” is certainly questionable – no Apple, no Garmin, no Withings, as yet, though it’s not currently clear if they might be revealed during the BBC show taking place on 28 January at 7:30PM. It’s also worth noting the Charge 2 isn’t the latest Fitbit – it’s over two years old – while Letscom and Letsfit wouldn’t be considered “popular brands” in the fitness tracker market.

This report isn’t the first to claim fitness trackers overestimate or underestimate some metric though, be it calories, steps or heart rate and it likely won’t be the last. Numerous trusted sources like Reuters and Which have also highlighted discrepancies in the past.

The question is however, does it actually matter if fitness trackers aren’t spot on with calories burned or if they are a few steps above or below actual steps taken? No, no it absolutely doesn’t.

It’s important they are within a reasonable parameter of accuracy of course, but fitness trackers are designed as motivational devices not as scientific absolutes.

The majority of people who buy them do so to ensure they are hitting 10,000 steps a day, or to track an elliptical session at the gym, or perhaps see how many hours of deep sleep they got. There will be few who expect a fitness tracker to deliver the levels of accuracy you could only get from being hooked up to numerous wires and medical machines.

The whole point in a fitness tracker is to highlight how much or how little you move and motivate you to do more. They remind you to stand up every hour or walk 250 steps an hour, for example.

So yes, a 50 per cent discrepancy is a surprising result from the likes of Fitbit, especially given its step and heart rate algorithms are great in our experience. But while fitness trackers may offer varying degrees of accuracy in terms of calories burned, or steps taken, or even heart rate, they will give you an estimation and this estimation can be a basis for motivation.

Ultimately, if strapping one of these little devices to your wrist helps you be fitter and healthier, have they not fulfilled their purpose?

Fitness trackers ‘overestimate’ calorie burning

Image caption The test involved a volunteer doing exercise with an oxygen monitor to accurately measure calorie usage

Popular brands of fitness trackers can overestimate the number of calories burned while walking by more than 50%, tests have found.

Researchers at Aberystwyth University found all products – ranging from £20 to £80 in price – were inaccurate during walking and running tests.

Dr Rhys Thatcher said devices had an “inherent tendency” to over-measure.

Fitbit said its product was based on “extensive research”, but others said theirs were “not medical devices”.

  • Female Fitbit users angry at period limits
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The tests, carried out for the BBC X-Ray programme, measured the amount of oxygen a volunteer used during ten minute walking and running sessions on a treadmill, before comparing it to the various fitness trackers.

The Fitbit Charge 2, which is the best selling fitness tracker on the market, was very accurate in testing calories burned while running, underestimating by 4%. But when measuring walking, it overestimated by more than 50%.

Cheaper devices – the Letscom HR and the Letsfit – underestimated the number of calories burned while running by 33% and 40% respectively.

But both were far more accurate in the walking test. The Letscom overestimated by 15.7% while the Letsfit was only 2% above the official measurement.

“If you want to know the exact number of calories that you are burning during an exercise session then it doesn’t matter which device you use, you have to interpret the data with some caution,” Dr Thatcher said.

Image caption Dr Rhys Thatcher from Aberystwyth University conducted the research

He added the inaccuracies were not important if they were being used as a motivational tool or to track progress.

Fitbit said it was confident about the performance of its product.

Letscom and Letsfit said their devices depend on data such as height and stride for accuracy and are not scientific devices, giving only estimations.

X-Ray is on BBC One Wales at 19:30 GMT on Monday 28 January

Heart rate? Age? Weight? How your stats factor in.

You knock out 45 minutes on the treadmill and the screen reads 480 calories burned. You crank out a solid one-hour spin class and check your fitness tracker: 670 calories. You check your phone after a fast-paced morning of running errands and your steps and energy expenditure app tells you you’ve burned 307, just from moving around to get things done.

We have a ton of devices and apps at our disposal to tell us how much we’re burning regardless of which activity we do. Burning calories means your body is turning the food you’ve consumed into usable fuel. We use a significant number of calories just to perform basic bodily functions–like breathing, digestion and growing cells–as well as to do more physically demanding tasks, like running, lifting, swimming and taking the stairs. The number of calories we need to meet our needs varies: your age, sex, weight, overall health and activity level will change your calorie needs and also impact how efficiently you use energy. As a very general rule, the number of calories you take in daily should not exceed the number of calories you burn.

Understanding what you’re burning during a workout can be a helpful tool if you’re interested in balancing your caloric intake with your caloric output, or if you’re looking for a way to assess how much your workouts are taking out of you. While you can use a formula to measure this for yourself, a device may be a more accurate way to know just what you’re putting out.

But how do these devices–the calorie burn meter on cardio machines or the fitness tracker you wear on your wrist – know how much you’re burning? Is this even the best data set to look at if you’re trying to boost your fitness or drop some weight?

Here’s what you need to know to get the most of your workouts and the information your devices provide.

What is your BMR?

Your resting or basal metabolic rate (BMR) is the amount of energy your body requires for its most basic functioning; basically, if you were laid up in bed, semi-conscious, the amount of calories you’d expend just staying alive is your BMR.

On top of this passive calorie burn you do without much thought, you also expend energy moving around: think spin class, barre workout, running after your kiddos or walking the dog.

Your body is unique in how it uses energy during activity

While the amount of energy we expend to survive remains pretty consistent, there are a few factors that impact how much you burn when you’re in motion (those extra, non-survival activities).

1. Body composition

Your body composition is a key component: the more lean muscle mass you have, the more you will burn at rest, as fat cells do not consume energy in the same way efficient way muscle cells do. (A pound of muscle burns an additional 1.5 calories daily; multiply this by your body weight and it’s a significant increase in burn across 24 hours.)

2. Body size and weight

Your body size impacts how much you burn as well: where two people weigh the same, the person with the larger frame is likely to burn more calories doing the same activity; however, a smaller person with more muscle mass may burn more (see above). Ultimately, the highest burn will come from a higher body weight made of a higher lean muscle mass percentage (the more muscle, the more you weigh, and the more you burn because of your active muscle cells and the act of moving more mass to complete a task.)

3. Age

With age comes a slower metabolism, meaning it takes more time or intensity to reach the same calorie burn doing the same activity compared to when you were younger.

How you exercise also impacts your overall burn

Any amount of movement will burn calories, but how much and how efficiently depends a lot on how intense your workout is and its total duration.

Aerobic and endurance exercise

When your cardiovascular system is working aerobically, it’s burning steadily and efficiently (think 60-70% of your max effort, at a pace you can maintain for at least 30 minutes). Endurance training primarily involves the aerobic energy pathway to convert stored fat to energy, which requires a large amount of oxygen. Your cells are receiving oxygen throughout the exercise and caloric burn rate is pretty regular.

This type of exercise – think jogging, leisurely cycling or dance – is effective for calorie burn but may require a longer duration to meet a specific calorie-burn goal; luckily, because it’s lower intensity, this can be easier as you can go longer without fatiguing.

High-intensity intervals

In these more anaerobic workouts, you’re doing short, fast, intense bursts of activity. Interval training combines short, high-intensity bursts of speed or power with periods of recovery built into one workout. Higher intensity interval requires the body to use both aerobic and anaerobic metabolism (glycogen and lactic acid) to help generate enough energy to fuel intense efforts.

Typically, a HIIT workout will be shorter in duration but higher in intensity than a low intensity, steady-state workout; basically, the difference between doing 15 stair sprints in a stadium versus 30 laps of the track at a more moderate pace.

Both of these types of exercise are valuable and burn calories: they draw on your system in different ways, however, so being adept at both is beneficial. To keep your body guessing (and efficient), it can be a good idea to aim for a combination of weight training, endurance work and hard interval sets across a week.

Strength training

It’s not cardio, but you still burn a ton of calories lifting or doing bodyweight strength work, especially if you incorporate sets for speed and power. Additionally, you’re building muscle mass, which ultimately boosts how efficiently your body processes calories.

Fitness trackers take some of these factors into account when you work out…

The device you wear on your wrist will factor in all of these things – your body and the intensity and type of exercise you do – to give you a read of your calorie burn. According to fitbit, their devices take into account your BMR (those calories your body burns to maintain vital functions). When you set up your tracker account, you enter your age, height and weight: these are all factored into a BMR typical of your stats. In addition to this baseline burn, your tracker will estimate – again, using your vital statistics – how much you burn during a workout. You enter ‘run’ and it calculates an average burn per minute of exercise you performed, based on the average performance of that activity of someone of your age and gender.

… so do treadmills, kind of

When you hop on the treadmill and are prompted to enter your age, gender and weight, this is part of the calorie-burn experience: the machine uses this data to generate an idea of how much you should burn. Cardio machines use standard formulas similar to those of fitness trackers, but with limited information and no details pertaining to your body composition, fitness level or size, the number is at best a ballpark.

The formulas used across fitness brands vary, but many are based on the generic Compendium of Physical Activities, a guide that gives the average burn (relative to sitting still) for a variety of activities. While good as a baseline, it does not take into account exercisers’ personal details.

Another factor that a treadmill cannot account for, but nonetheless impacts your calorie burn is your form: the more efficient you are with your stride and your arm swing, the less you will burn, even if you’re working at the same intensity as a newer runner. In this situation, being more fit means burning less, as the extra burn for less-experienced runners comes from more ancillary motion, like bouncing up and down, not necessarily voluntary motion. The burn is higher but the run is less functional.

The limitations of tracker and treadmill calorie counts

While having an outline of your caloric expenditure workout to workout, the drawback to using your tracker or the readings on a machine are just estimates: without highly specialized, personalized formulae, a device can’t truly give you a perfect reading of what you’ve burned.

A study at Stanford University assessed different devices to check their accuracy. The results showed that the most accurate of them was off by an average of 27 percent and the least accurate by 93 percent.

Instead of using the number as a means to justify eating an additional meal every day, consider the calorie count a basic indicator of how hard you worked. You can use this to measure your progress and intensity across days and weeks. To get an even more personalized read of your intensity, gauge your workout using a heart rate monitor or a scale system for perceived exertion. If you’re really keen on knowing your caloric burn, you can use metrics like heart rate and body composition to get a clearer read.

Overall, the most useful indicator of how hard you’re working – and thus, your caloric burn – is how you feel during the workout. Push hard, take breaks and hydrate well to keep your heart rate and your endurance up. Overall, the more you move, the harder you work and the more efficiently you perform an exercise, the more you’ll burn… all things your tracker will have a tough time quantifying.

Do fitness trackers really work? Probably, but it’s not as simple as you think!

As some of you may know, I’m not only a tech lover — I’m also a big fitness enthusiast. Therefore, the idea of a fitness tracker — which combines tech and fitness into a single product — seems right up my alley. Getting all your biometrics right on your wrist and seeing your progress charted over time is like something from a superhero movie.

There are practical, less nerdy benefits too. A fitness tracker should help you lose weight, improve your fitness, and adopt healthier habits around sleeping, eating, exercising, and moving.

Do fitness trackers really work, though? What is your fitness tracker actually measuring anyway? Just how accurate is it really?

As much as I love this tech, I can see some serious inherent problems. Even if this information is accurate, is it even useful?

The concept

To find out whether fitness trackers really work, first we need to know precisely what they do. Fitness trackers come in all shapes and sizes, and include a wide variety of different sensors and features depending on the brand. Almost universally, they rely on a heart rate monitor to calculate rough calorie expenditure and motion sensors to detect movement.

The premise is simple: the harder your heart is working, the more you’re exerting yourself, the more calories you are burning.

Now if you measure the calories coming in via a diet app like MyFitnessPal, you can see the difference and attempt to maintain a “deficit.” If you consume less than you use, your body burns fat and you lose weight. If you consume more than you use, your body has a surplus of calories, which it stores as fat — you gain weight.

It’s simple math, but it has loads of problems.

The problem with heart rate monitors

The heart rate monitors used in most trackers work via a technology called pulse oximetry. An infrared light penetrates the skin and looks for subtle changes in the color of the blood. These colors represent the oxygenation of the blood, which increases with each heartbeat.

This technology is far from perfect. Many other things can impact blood oxygenation or otherwise change the appearance of the blood vessels. When you’re lifting weights, contractions alter the amount of blood reaching the limbs, so do changes like vasodilation. This is why chest-worn heart rate straps are more reliable than wrist-worn devices.

The best fitness trackers use complex algorithms analyzing movement to ascertain what activities you are engaging in and alter the heart rate interpretation accordingly. These are best described as guesstimates.

Those aren’t the only problems. Heart rate alone is not an ideal indicator of calorie burn. The assumption is that when the heart pumps faster, you are creating a demand for oxygen and energy and thus probably engaging in an activity that is “costly” from an energy perspective.

In reality, many things can increase your heart rate. Fitter individuals actually have lower resting heart rates because the strength of each heartbeat is greater — allowing their hearts to beat less frequently. Blood pressure, air pressure, ambient temperature, mood, and more can all impact on your heart rate.

A good gaming session will raise your heart rate, but you won’t burn many extra calories!

To be fair, good fitness trackers don’t rely on the heart rate alone. They measure combinations of heart rate and movement, compared against patterns derived from huge data sets using machine learning. Regardless, it is still ultimately an inaccurate picture.

Finally, it’s also problematic that most smartwatches only take a measurement of your heart rate once every few minutes or so, unless you are engaged in some kind of workout. This is intended to conserve energy, while allowing for an average resting and maximum heart rate. The amount of calories you burn during a gym session actually only has a small impact on your total daily calorie expenditure. Far more important are your levels of activity throughout the day. Your smartwatch may remind you to get up and walk around every now and again, but it might also miss your quick impromptu dance routine in the kitchen.

The number of calories you burn during a gym session actually only has a small impact on your total daily calorie expenditure

It’s very possible the real secret to impressive weight loss is just to be more energetic and active throughout the day — and your fitness tracker has no way of effectively tracking this. Whether fitness trackers actually work depends on if you’re a runner or a weightlifter, or whether you’re looking to lose weight throughout the day, or just during your workouts.

Do fitness trackers really work?

What’s even more concerning is what is ultimately done with all this information.

The central hypothesis driving the smartwatch industry is that losing weight is a simple matter of “calories in versus calories out.” This view is held by many fitness experts, bodybuilders, and nutritionists. But not all.

Calories in – calories out = weight loss?

Another crowd maintains that counting calories is actually ineffective for a large number of the population. According to this perspective, the answer has more to do with metabolism, hormone balance, insulin sensitivity, gut bacteria, nutrient density and so on. These people push intermittent fasting, ketogenic diets, and the paleo lifestyle. This group might answer the question of whether fitness trackers really work quite differently.

Allow me to be so bold as to present my take.

Burning more calories than you consume will result in weight loss. However, we have no idea how many calories we’re actually burning a lot of the time.

Smartwatches and the calorie-counting crowd rely on a number called an Active Metabolic Rate (AMR) to do their math. This is the number of calories that you burn during a normal day of activity. In turn, this is calculated as your Basal Metabolic Rate (BMR) — the number of calories simply required for breathing and thinking — plus any activity on top.

To get your BMR and therefore your AMR, enter your height, your weight, and sex. This is necessary because taller people require more energy just to go about their usual business — that’s why bigger folks tend to eat more. Likewise, men and women burn slightly different amounts of calories — with women usually requiring a little less food on a daily basis.

There’s a glaring omission here: muscle mass.

Muscle is metabolically active — it requires energy to maintain and to use. Someone who is 165lbs and very muscular will burn more calories than someone who is 165lbs with no muscle.

Pack on muscle and your fitness tracker may become less accurate…

There are ways around this. You can do a similar BMR calculation using your lean body mass, which is a much more useful figure for learning calories burned. Very few fitness trackers allow you to enter this information. None that I know of ask for a body fat percentage by default. Most users would likewise understand why that might be a problem.

However, the problem runs much deeper than that. Individual differences when it comes to calories burned don’t just come down to body weight and muscle mass. Two people roughly the same height and weight probably won’t burn the same number of calories.

If you have a higher level of testosterone for instance then you will burn more calories and build more muscle

Hormone balance plays a big role here. If you have a higher level of testosterone, you will burn more calories and build more muscle. Likewise, thyroid hormones, cortisol levels, insulin, and more all play a role.

Don’t believe that hormones can make that much difference to your physique? Look at someone who uses steroids. They would have the same numbers as anyone else on a fitness tracker, but they’d look a whole lot different.

Now I’m not suggesting you use steroids, but while you might not have the sky-high testosterone levels of someone who uses them, a slightly higher or lower number could still have a more minor impact on your weight loss.

Likewise, many women who start using oral contraceptives will find they either gain or lose weight as a result.

Similarly, many health conditions like hypothyroidism can drastically alter the way your body uses energy from food. You might not have hypothyroidism, but if you are struggling to lose weight despite what the numbers are saying, you might still have a slower metabolism than average. It’s better to think about these things as spectrums, rather than binaries in many cases.

Many other things might influence your actual BMR too, such as your gut bacteria. Our guts harbor a lot of friendly bacteria that we are increasingly learning plays a very vital role in our health and wellbeing. These critters help us to produce hormones and neurotransmitters, they aid with our digestion, and they fend off bad bacteria. Several case studies have shown us that fecal transplants (yep it’s what it sounds like!) can result in rapid weight loss or weight gain thanks to the loss or addition of the bacteria.

If it were possible to precisely count calories going in and out, this would lead to more accurate predictions of weight gain or weight loss. However, our idea of how to calculate calorie burn is probably pretty primitive, and the resulting number might end up being more misleading than helpful. This all casts some doubt when asking if fitness trackers work.

Should I throw out my fitness tracker?

If all this sounds very negative, forgive me. I’m actually a big fan of fitness trackers.

For most people, the calorie calculations are accurate enough to be useful. Calorie restriction is a great place to start, and it’s only when you find it doesn’t work that you need to start considering other options to improve your metabolism and general health and fitness.

As Tim Ferriss points out, sometimes just having a single metric to track can be incredibly valuable — even if that metric isn’t completely accurate or doesn’t paint a complete picture. Do fitness trackers work? If it’s been working for you, then yes! I know plenty of people personally who have lost weight using them.

That’s really where fitness trackers come into their own. They are highly useful devices for simply letting us track our general levels of activity and to identify areas where we could be doing better. Trying not to break the chain is a seriously motivating reason to keep going to the gym or to keep your calorie intake low (just as Seinfeld.)


Of course, fitness trackers also do much more than just count calories and steps — they’re useful for training in heart rate zones (see my post on seven minute workouts), and they provide sleep tracking, meditation modes, and more. I’m really excited for the future of these devices and how they might be able to advise us on our chronotype, or look at our heart rate variability to estimate recovery. Projects like the Oura Ring show promise in this regard.

Even by simply making us more aware of more aspects of our health, any fitness tracker can help improve many areas of our lives. That which is measured, improves.

Just understand the limits of these devices. Don’t take their results as law. There’s far more going on in our bodies than they can measure, or than even we fully understand. It’s not as simple as just asking do fitness trackers work. Nothing about the body is simple!


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Does fitbit overestimate calories burned

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