Can You Trust the Results Your Tracker Delivers?

Can you really trust your tracker? Members often share their doubts on the SparkPeople message boards. "My fitness tracker shows that I'm burning about 600 calories through daily exercise. My calorie range then increases to 1,800 to 2,150. Can I really expect to lose weight by eating that many calories?" one member pondered.
As a registered dietitian, my typical response for years has been this: Be careful with "eating back" all those calories you burn through exercise based on your fitness tracker. Honestly, I'm with the many skeptical members, having never really trusted the calories burned report on trackers, and guess what? We were right—these fitness gadgets are no good at accurately reporting the calories you burn. 

The Research

A recent research study conducted by the Stanford University School of Medicine evaluated the accuracy of wrist-worn activity trackers in reporting energy expenditure, commonly referred to as calories burned. The study, published in the Journal of Personalized Medicine, evaluated the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and Samsung Gear S2. These devices were strapped to 60 volunteers (29 men and 31 women) who underwent a range of activities, such as sitting, walking, running and cycling. At the same time, the participants were being assessed using an indirect calorimetry machine that calculated actual metabolism by measuring oxygen and carbon dioxide in the participants' breath. Then, the data from the tracker was compared to the data from the indirect calorimetry machine.
The results showed that these fitness trackers basically "flunked" when it came to measuring how many calories a person burns through activity and exercise. None of the seven devices measured energy expenditure accurately. That's right—none of them. The inaccuracy ranged from 27 to 93 percent, which means that the worst performing device was wrong a whopping 93 percent of the time and even the best performing device was still inaccurate 27 percent.
Another interesting finding from this study was that there was even "greater error" in people with darker skin, tattoos, higher BMIs and men; the error was slightly less for Caucasian women and those with a healthier BMI, which is an issue since most SparkPeople members set a weight-loss goal due to their higher BMI. Therefore, relying on the calories burned information from a fitness tracker could be greatly impacting one's weight-loss effort.

Adjusting Your SparkPeople Program for Improved Accuracy

Until fitness trackers can accurately measure energy expenditure, you may want to do some investigation and make adjustments to your SparkPeople program. Realize that the program used at SparkPeople to determine your calorie range already calculates the calories you burn at a resting state (metabolism) and uses the lifestyle activity factor (sedentary, lightly active or active) that you selected when you joined the site. This activity factor accounts for your movement throughout the day outside of exercise, including as daily chores and your job. If needed, you can adjust that setting here
There are two different ways to account for your planned exercise in your program setup: The first is to connect your fitness and nutrition trackers so that when you track exercise, your recommended calorie range changes accordingly. The second is to disconnect communication between your fitness and nutrition tracker, so your calorie range is based on a calories-burned goal and does not fluctuate depending on the activity you track. Regardless of which method you use, it's important to be sure your activity tracker is not overstating your calories burned, resulting in a calorie range that's too high to help you reach your weight-loss goals.
An easy way to check the calories burned through your planned exercise versus the numbers the activity tracker is providing is by using SparkPeople's "Calories Burned List." Manually add up your exercise using this list as a reference, then compare to the results given by your activity tracker. Do this for a week or so to get a good idea of how close those numbers are to one another.

After those days pass, evaluate your results. If you discover that your activity tracker and your manual calculations are similar, then leave your program as is. If, however, you notice a discrepancy between these two values, then you may want to change the method that you use to determine your calorie range within the SparkPeople program. If the latter is true, you have one of two options, the first of which assumes you will disconnect your activity tracker from your SparkPeople account and the second which assumes that your tracker will remain connected.

Option #1

If your fitness and nutrition trackers are not connected:  
Disconnect your activity tracker from your SparkPeople program so that the calories you burn through planned exercise is not changing your calorie range daily. Adjust the calories burned weekly in your SparkPeople program to match what you are typically doing. Now you will have a calorie range that is a better reflection of your exercise plan. 
If your fitness and nutrition trackers are connected:
Disconnect your activity tracker from your SparkPeople program and manually track your exercise daily. Your calorie range will change depending on the calories burned, but this range will be a better reflection of the exercise you're actually doing.

Option #2

If your fitness and nutrition trackers are not connected:
Keep your activity tracker connected to your SparkPeople program, but set your calories burned goal so that you're only"eating back" half the calories your activity tracker shows you are burning daily. This should be close to the amount you manually calculated during your experiment.
If your fitness and nutrition trackers are connected:
Keep your activity tracker connected to your SparkPeople program, but only opt to "eat back" half the calories you are burning daily through your planned exercise or the whole amount you manually calculated during your experiment.
Bottom Line: Before you trust the calories burned report from your activity tracker, do some experimenting and investigation to determine accuracy. Make the necessary adjustments as you prefer to ensure that your calorie range jives with those weight-loss goals you're working so hard to achieve. 
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Member Comments

BMR is key Report
thank you Report
Great article! Report
I have a Fitbit Zip. It works like the Smart People Activity Tracker did: counts steps, burned calories, mileage, and gives the time. Every time my husband go out on the boat, I end up with thousands of steps that I didn't take! It's counting all those rolls of the water and bounces up and down the boat makes at high speeds as steps. Report
I figured out how many calories I need to maintain my body weight. The “eat back” calories are a back up do I don’t feel guilty for the occasional special occasion : bday, anniversary, a sale on muffins... Report
I figured out how many calories I need to maintain my body weight. The “eat back” calories are a back up do I don’t feel guilty for the occasional special occasion : bday, anniversary, a sale on muffins... Report
Since I don't "eat back" the calories burned it doesn't really matter, My fitness tracker is just a guide. Report
I would say sometimes. I have a pedometer and it reset while I was at church today. 😔 Report
I do like to track my heart rate since I have high blood pressure and take meds designed to slow my heart rate down. I’ve suspected that complication messed up the calories burned count for a long time. I also don’t trust the calories listed on food labels. This is a game of estimating based on bad information from food manufacturers and logarithms that can’t account for a persons individual situations. It’s not easy. If it were easy we’d all have lost the weight already. Report
I use my Fitbit (love it) not as a guide to how many calories I have burned but more as a guide to count my steps, track my heart rate (although in a general sense), track my sleep, and as a reminder to get up an move every waking hour. Since I have never added the exercise calories to my daily total the “calorie burn” aspect of my tracker has never been a major point for me.

I do have my tracker synced, but use it mostly for steps and sleep. I always manually enter exercise but ignore the additional calories added for exercise in my nutrition tracker. I find unless you check each item in the nutrition tracker you are frequently adding items that are incorrect in some form to your daily food. That seems to be the biggest drawback to having members add foods, calories too low, sodium missing, protein way too high, or other nutrients missing or inaccurate are the most common mistakes I find routinely. Whenever I add a food that I haven’t used lately I always check, it is irritating to find 6 different calorie amounts for one item. I also do not like foods that are measured in inaccurate ways, like measuring cooked pasta by the cupful. The only accurate way to measure pasta is dry weight. Report
I finally realized my Fitbit wasnt as accurate as I thought when I was trying reach my goal weight. I finally figured it was off about 20-25%. Once I figured that out, I was able to lose the remaining weight. I still love my tracker though bc I love statistics even if they aren't completely accurate! Lol 😁 Report
Thank You for the information......
....... Report
Thanks for the information. Report
Thank you! Report


About The Author

Becky Hand
Becky Hand
Becky is a registered and licensed dietitian with almost 20 years of experience. A certified health coach through the Cooper Institute with a master's degree in health education, she makes nutrition principles practical, easy-to-apply and fun. See all of Becky's articles.