Is the FitTrack Scale Accurate?
The FitTrack Scale (Dara Scale) has captured my attention due to its massive amounts of social media ads and steadily climbing Alexa rank, not because it is a bioimpedance scale with an app that tracks your progress on “important” metrics.
The Fittrack Scale
In reviewing the FitTrack Scale, two questions came to my mind:
- Is the Dara Scale accurate?
- Are the metrics it provides useful and important?
Before I get into the accuracy of the FitTrack Scale, I want to dive into the uselessness of some of the information the scale tracks.
Body Mass Index
The only reason body mass index (BMI) is so often used as a measurement is because it has been around for a long time and is used as a standard, which is a symptom of “That’s just the way things are done around here,” and not of any use of the measurement. BMI is simply a calculation based on the height and weight of a person, which becomes skewed, even by its own formula, for those that fall outside of the typical height range. Simply put:
According to mathematician Nick Trefethen, “BMI divides the weight by too large a number for short people and too small a number for tall people. So short people are misled into thinking that they are thinner than they are, and tall people are misled into thinking they are fatter.” Moreover, BMI does not account for important factors such as muscle mass (for instance, a bodybuilder with very low body fat is likely to be declared “obese”), bone density/frame, racial differences, or even sex. Yes, you read that right. A woman and a man of the same height and weight will record the same number. The measurement is so utterly useless it has been declared not just downright stupid, but unethical for use in some publications.¹
FitTrack Scale’s Atrocious Advice
In mindlessly following BMI recommendations, the FitTrack Scale declared my “ideal weight” right around the measure of my muscle mass, as in some days my muscle mass weighs a bit more than my “ideal weight,” and other days it weighs a pound or two less. FitTrack’s algorithm simply spits out an “ideal weight” based on my height, disregarding my current body composition, goals, etc.
For context, the Dara Scale set my goal weight to 149.7 pounds (I’m 5’11), a weight my muscle mass measured by their device exceeds on many days. I don’t think I could get to 149.7 pounds and be reasonably fit or healthy. The lowest I have ever weighed, with low body fat while eating a strictly regimented diet and training 4+ hours a day 6 days a week, was a little over 170 pounds. Losing another 10 pounds would have taken me to fat levels low enough for bodybuilders in competition, meaning that the only way to lose further weight would have been to drop muscle, and the only way to be at a healthy weight would have been to drop considerable muscle.
Since my body is inclined to put on muscle no matter the activity (i.e., doing more kickboxing has significantly and noticeably increased my upper body muscle mass, despite no weighted resistance training), to get to FitTrack’s recommended weight, I would need to stop exercising. Having this as a “goal” on an app I see daily may make me shake my head, but it may give someone else anxiety and a negative body image.
FitTrack Dara Scale’s Accuracy
The first red flag was my body water percentage, which barely fluctuated despite my best efforts (i.e., it did not matter whether I was at the end of a 120-hour fast, or whether I was purposefully loading on water). My highest recording for hydration was 54.9% and my lowest 52.8%, both of which the FitTrack Scale declares as “low.” For context, I drink water all day long until I can’t anymore, approximately 8 liters a day. Other than first thing in the morning when I am deep into a fast, the color of my urine is consistently clear.
Let’s take a look at 30 days of my recorded data:
| Measurement | Weight (lbs) | Fat Mass (%) | Muscle Mass (lbs) | Bone Mass (lbs) | Water % |
|---|---|---|---|---|---|
| 1. Unfasted | 223.1 | 58.4 | 152.8 | 7.7 | 53.0 |
| 2. 36hrs fasted | 219.1 | 55.3 | 149.5 | 7.7 | 53.0 |
| 3. 12hrs fasted | 216.5 | 53.8 | 147.3 | 7.7 | 54.0 |
| 4. 36hrs fasted | 213.8 | 51.8 | 144.8 | 7.5* | 54.0 |
| 5. 12hrs fasted | 218.0 | 54.7 | 148.6 | 7.7 | 53.6 |
| 6. 12hrs fasted | 223.5 | 58.6 | 153.2 | 7.7 | 52.8 |
| 7. 12hrs fasted | 220.2 | 56 | 150.4 | 7.7 | 53.3 |
| 8. 36hrs fasted | 214.3 | 52 | 145.3 | 7.5* | 54.1 |
| 9. 60hrs fasted | 212.3 | 50.9 | 143.3 | 7.5* | 54.4 |
| 10. 84hrs fasted | 211.2 | 49.8 | 142.9 | 7.5* | 54.7 |
| 11. 108hrs fasted | 209.9 | 48.9 | 141.5 | 7.5* | 54.9 |
| 12. 12hrs fasted | 213.4 | 51.1 | 144.6 | 7.5* | 54.4 |
| 13. 12hrs fasted | 217.4 | 54.0 | 147.9 | 7.7 | 53.8 |
| 14. 36hrs fasted | 214.3 | 52.2 | 145.1 | 7.5* | 54.0 |
| 15. 12hrs fasted | 213.8 | 51.8 | 145.1 | 7.5* | 54.2 |
| 16. 36hrs fasted | 210.8 | 49.8 | 142.2 | 7.5* | 54.6 |
| 17. 12hrs fasted | 213.4 | 51.4 | 144.6 | 7.5* | 54.0 |
| 18. 12hrs fasted | 215.8 | 52.9 | 146.8 | 7.7 | 54.0 |
| 19. 12hrs fasted | 219.6 | 55.8 | 149.9 | 7.7 | 53.3 |
| 20. 12hrs fasted | 217.8 | 54.5 | 148.4 | 7.7 | 53.6 |
| 21. 36hrs fasted | 211.6 | 50.3 | 143.1 | 7.5* | 54.6 |
| 22. 12hrs fasted | 214.7 | 52.5 | 145.5 | 7.5* | 54.1 |
| 23. 36hrs fasted | 211.0 | 49.8 | 142.4 | 7.5* | 54.7 |
| 24. 36hrs fasted **several days out of town |
213.0 | 51.1 | 144.2 | 7.5* | 54.4 |
| 25. 12hrs fasted | 214.3 | 52 | 145.3 | 7.5* | 54.2 |
| 26. 0Hrs fasted | 221.8 | 57.5 | 151.7 | 7.7 | 53.0*
Could not consume any more water; water loaded for 2 days. No exercise was done the day before measurements. |
| 27. 12hrs fasted | 218.9 | 55.3 | 149.3 | 7.7 | 53.4 |
| 28. 12hrs fasted | 221.1 | 57.1 | 151.0 | 7.7 | 53.1 |
| 29. 12hrs fasted | 219.1 | 55.6 | 149.5 | 7.7 | 53.3 |
| 30. 36hrs fasted | 214.5 | 52.0 | 145.5 | 7.5* | 54.1 |
*Obviously, there are accuracy problems with the FitTrack scale. For instance, it is impossible for me to gain or lose multiple pounds of muscle and/or fat on a day-to-day basis. Many technologies have a hard time differentiating between water, food, and lean mass, such as muscle. Also, variables such as skin temperature,² ambient air temperature, ³ and you leaning on the scale, etc., have been known to play a role in the results, which is why some researchers have suggested the technology has limited use in large epidemiological studies.⁴
Testing the FitTrack Dara Scale in Various Situations
I decided to see how much some of these factors played a role by running back-to-back assessments with measurements taken as control, leaning on the scale, and squatting, as well as stepping on the scale with cold feet and with hot feet (all done within 30 minutes, with no food or water consumption during this period).
Feet Cooling
I did this for 5 minutes in an ice bath.
Feet Warming
I did this for 5 minutes in a hot foot bath.
Note that your feet need to stay on the sensors. This position limits how much you can learn.
Test 1
| Measurement | Weight (lbs) | Fat Mass (lbs) | Muscle Mass (lbs) | Bone Mass (lbs) | Water % |
|---|---|---|---|---|---|
| Normal foot temperature, standing straight | 218.3 | 54.7 | 148.6 | 7.7 | 53.6 |
| Cold feet from the ice bath | 218.3 | 54.7 | 148.6 | 7.7 | 53.6 |
| Hot feet from the hot bath | 218.3 | 54.5 | 148.8 | 7.7 | 53.7 |
| Normal foot temperature, leaning to one side | 218.3 | 53.6 | 149.5 | 7.7 | 54.0 |
| Normal foot temperature, squatting low | 218.3 | 53.6 | 149.7 | 7.7 | 54.0 |
Test 2
| Measurement | Weight (lbs) | Fat Mass (lbs) | Muscle Mass (lbs) | Bone Mass (lbs) | Water % |
|---|---|---|---|---|---|
| Normal foot temperature, standing straight | 215.4 | 52.7 | 146.2 | 7.5 | 54.0 |
| Cold feet from the ice bath | 215.4 | 52.7 | 146.2 | 7.5 | 54.0 |
| Hot feet from the hot bath | 215.4 | 52.5 | 146.2 | 7.5 | 54.1 |
| Normal foot temperature, leaning | 215.4 | 52.7 | 146.2 | 7.5 | 54.0 |
| Normal foot temperature, squatting low | 215.4 | 53.1 | 145.9 | 7.5 | 53.9 |
Test 3
| Measurement | Weight (lbs) | Fat Mass (lbs) | Muscle Mass (lbs) | Bone Mass (lbs) | Water % |
|---|---|---|---|---|---|
| Normal foot temperature, standing straight | 215.6 | 53.1 | 146.4 | 7.7 | 53.9 |
| Cold feet from the ice bath | 215.0 | 52.7 | 145.7 | 7.5 | 54.0 |
| Hot feet from the hot bath | 215.0 | 52.5 | 145.9 | 7.5 | 54.1 |
| Normal foot temperature, leaning | 214.9 | 52.5 | 145.9 | 7.5 | 54.0 |
| Normal foot temperature, squatting low | 215.0 | 52.5 | 145.9 | 7.5 | 54.0 |
There were erratic and inconsistent changes within these measurements on the 3 days I ran this experiment, showing that consistency is needed.
FitTrack Scale vs. DEXA Scan
Next, I decided to compare my results measured by the FitTrack Scale vs. those measured by DEXA Scan, which is often called the “gold standard” of body mass analysis.⁵ Originally, I planned on testing with three different scenarios to measure the accuracy of FitTrack; however, upon discussing points with the technician, I realized this would also demonstrate the flaws of the DEXA Scan. These flaws include the following:
- The DEXA scan doesn’t measure water percentage, but water and food consumed would likely have an effect on the “lean mass.”
- The location I went to said you can throw off a DEXA scan by loading on water or food beforehand.
- The onsite trainer further told me that numbers yielded by the scan were “largely inconsistent” depending on your diet, i.e., carb-loading or while in ketosis, due to depleting glycogen stores.
Dehydration and having an empty stomach could also affect the results.
FitTrack Scale vs. DEXA Scan Test #1
Preparation:
5-day water fast leading to an empty stomach, dehydration, and depleted glycogen stores
| Technology | Weight (lbs) | Fat Mass (lbs) | Muscle Mass (lbs) | Bone Mass (lbs) | Water % |
|---|---|---|---|---|---|
| FitTrack
108hrs fasted |
209.9 | 48.9 | 141.5 | 7.5 | 53.0 |
| DEXA
109hrs fasted |
207.3 | 63.4 | *LEAN
138 |
6.0 | **DNM |
*Lean mass, which includes water and foot, and not muscle mass
**Does not measure
FitTrack Scale vs. DEXA Scan Test #2
Preparation:
Overnight fast (while staying hydrated)
| Technology | Weight (lbs) | Fat Mass (lbs) | Muscle Mass (lbs) | Bone Mass (lbs) | Water % |
|---|---|---|---|---|---|
| FitTrack
14hrs fasted |
214.7 | 52.5 | 145.5 | 7.5 | 54.1 |
| DEXA
15hrs fasted |
217.7 | 63.7 | *LEAN
148 |
6.0 | DNM |
FitTrack Scale vs. DEXA Scan Test #3
For this test, I had decided to do the opposite of the 5-day water fast. I carb-loaded for 3 days leading up to the test and hydrated as much as I could the entire time. On the day of the test, I ate a plate of pasta and some sourdough bread and drank as much water as possible. In fact, I forced myself to drink 4 liters of water before stepping on the FitTrack and then held off my intense need for urination for an hour, until the DEXA scan was completed.
Preparation:
- A full stomach of food, as hydrated as possible
- 3-day carb loading
| Technology | Weight (lbs) | Fat Mass (lbs) | Muscle Mass (lbs) | Bone Mass (lbs) | Water % |
|---|---|---|---|---|---|
| FitTrack
0hrs fasted, full stomach, fully hydrated |
221.8 | 57.5 | 151.7 | 7.7 | 53.0
*Could not consume any more water; water loaded for 2 days. No exercise was done on the day of the test before taking measurements. |
| DEXA
1hr fasted, full stomach, fully hydrated |
220.8 | 62.9 | *LEAN
152.2 |
5.7 | DNM |
The DEXA scan showed that I had gained a whopping 14.2 pounds of lean mass in just 3 weeks. Astonishing! Of course, my actual weight remained rather consistent and I likely neither gained nor lost any lean mass. The FitTrack seemed to evenly split my water and food as muscle and fat, which was an interesting, yet equally inaccurate result.
Takeaway From FitTrack Scale vs DEXA Scan TestTests
For both technologies, the level of extreme susceptibility to confounding variables that most consumers would never think of, i.e., consistent eating habits, hydration, and even temperatures of surrounding air and skin (for home scales), could lead to either frustration at a lack of progress or a false sense of improvement. In an extreme but realistic scenario, people could be exercising, watching what they eat, and making all-around great choices, but the variable conditions prior to their measurement could make it appear that their body composition had declined. This type of negative feedback could derail their health efforts, removing the motivation to continue investing in their efforts.
This is an important lesson: If you don’t properly control your testing parameters, any body mass measurements you make, whether it be via bioimpedance, DEXA scans, or any other technology, will produce inconsistent results. Although none of these measurements are truly accurate, they should still be accurate against your own results. You should be able to observe any potential changes if you simply control some specific variables before taking the measurements: (i.e., room and skin temperature, dietary habits and behavior immediately before the test, hydration, etc.). Therefore, you should avoid inconsistent testing (e.g., measuring one day after working out and on an empty stomach, then the next day after an all-you-can-eat buffet). There is no useful information you will attain from inconsistent measurements.
I want to take this opportunity to announce that the not-for-profit I have been hinting at, which will offer tutorials on these basic principles and give templates for self-experimentation, is slowly gearing up to start beta testing. I hope that by the time this newsletter goes out, we will be able to start taking sign-ups for more information on when we launch. Check us out here: myjourney.science
1 https://journals.physiology.org/doi/abs/10.1152/jappl.1996.81.2.838?journalCode=jappl
2 https://iopscience.iop.org/article/10.1088/0967-3334/25/1/011
3 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2543039/
4 https://www.jsams.org/article/S1440
