5 Best Metabolism Trackers for Weight Loss (2023)

Resting metabolic rate (RMR) and basal metabolic rate (BMR) are usually measured with a calorimeter in a laboratory setting, which most of us don’t have access to. 

And it essentially tells how many calories your body needs to survive, but it doesn’t tell you if your body is burning fat or not.

The best metabolism trackers, on the other hand, help you to understand how your body reacts to certain foods and if you are burning fat or carbs for energy.

Top Options


Best Metabolism Tracker


Best for Low-Carb Diets


Best Metabolism Test
MyLab Box

Best Metabolism Trackers

1. Lumen


What We Liked

  • Best metabolism tracker for weight loss
  • Works well with low-carb diets but isn’t as restrictive as keto
  • Well designed and feels premium in hand
  • Effective as a motivational tool to actually lose weight
  • App offers recipes, and you can add or remove ingredients
  • Provides precise RER measurements (peer-reviewed)

What Can Be Improved

  • Sometimes the app asks several times to take measurements
  • Measurements sometimes take more time compared to Keyto
  • Doesn’t have a screen, requires an app to take measurements

Lumen is a metabolism tracker device that measures CO2 concentration in your breath and tells you if your body is using carbs or fats for energy. 

According to Lumen, tracking your metabolic flexibility makes it easier to lose weight, build lean mass, and get better sleep.

What I liked about the Lumen metabolism breathalyzer is that it gives me a holistic overview of my health, metabolism, and weight loss status, compared to keto breathalyzers that measure only ketones.

I liked that it covered everything from nutrition plans to workouts to the community to meal timing, so I didn’t have the “what now” moments that I had with other weight loss tools.

  • In the beginning, I found it frustrating to exhale with the right intensity, and it asked me to repeat it several times. It does have visual guidance, so the problem was in me, not in the device.
  • Another thing I didn’t like is that because the device doesn’t have a screen, I was forced to check my phone first thing in the morning to check my readings. This, again, isn’t a dealbreaker, but it would be nice to see the readings data without the phone. 

Lumen metabolic measurement device helps you to improve metabolism flexibility so you are better able to burn fat instead of carbs, leading to weight loss.

This is a great alternative to restrictive diets like keto, which do work, but do require more effort.

Lumen technology is validated through peer-reviewed studies and utilized in research with the scientific community, so there’s actual science behind it, not random mumbo-jumbo

ResultsIn 10 seconds
MethodBreath test
MetricsCO2 concentration
Best forHolistic weight loss

2. Biosense


What We Liked

  • Best metabolism monitor for the keto diet
  • FDA-registered Class I medical device backed by clinical trial data
  • Has a screen, so you don’t need to use a smartphone first thing in the morning
  • Automatically syncs with the app for convenient tracking
  • Uses end-of-breath sampling for the most accurate reading
  • Haptic feedback tells you when to stop breathing into the device

What Can Be Improved

  • Takes a bit to warm up before you can use it
  • Device homepage is cheaply designed, doesn’t build trust
  • A higher price tag

Biosense is the best metabolism tracker device for low-carb diets. It shows you your real-time metabolic response after you sleep, eat, fast, and exercise.

This metabolism tester measures acetone levels in your breath and tells you if you are burning fat or carbs for energy, which is the most important for weight loss.

I really like that it provides historical data trend about my progress and a fasting clock that help me to stay in ketosis.

The coolest feature is that when blowing into the device, you feel a subtle haptic feedback sequence of two short bumps that indicates when to stop blowing.

  • The main negative aspect, I feel, is that they suggest recalibration of the sensor every 6 months. You will need to ship it to Biosense, and once they recalibrate the sensor, they will send it back to you.
  • The process will take 6-10 days and, after the first year of warranty, will cost $74.99.
  • This recalibration process definitely feels annoying, especially when you need to pay for it. At the same time, if high accuracy is important to you, it’s definitely worth it.

I also really liked that it has a screen for fast readings, so I don’t need to watch my phone screen first thing in the morning.

Biosense metabolism tracker is FDA Class 1 medical device and currently going through clinical trials.

ResultsIn 10 seconds
MethodBreath test
Best forLow-carb/keto dieters

3. MyLab Box At Home Metabolism Test

What We Liked

  • Easy and accurate at home finger prick and saliva test
  • Rather affordable price point
  • Fast shipping and you get results in 2–5 days
  • Checks key metabolism indicators: cortisol, testosterone, and thyroid-stimulating hormone
  • Analyzed in CAP and CLIA certified laboratories (CDC listed)

What Can Be Improved

  • Some have complained about slow customer support
  • Blood sample requires a finger prick

MyLab Box offers the best at home metabolism test because they offer fast, free shipping and the most precise metabolic test results.

This DIY metabolism test uses finger prick and saliva testing to measure cortisol, testosterone, and thyroid-stimulating hormone (key metabolism indicators).

The metabolism test shows you how the underlying metabolic and dietary factors are currently impacting your health, whether negatively or positively. It also offers some information about lifestyle changes to improve abnormal levels if needed.

It’s a DIY home-based test that I received in 2 days. I just took a saliva sample by spitting into a tube and a blood sample by pricking a finger. 

Then I just send a prepaid envelope with my tests to the testing lab. MyLab uses certified laboratories which are CAP and CLIA certified and CDC listed.

Some users have complained about the slow customer support, but I got a fast response when I asked about shipping, so do your own testing.

ResultsIn 2-5 days
MethodBlood and saliva test
MetricsTSH, cortisol, testosterone
Best forHealth testing

4. Keyto 


What We Liked

  • Best keto metabolic tracker
  • Provides accurate readings
  • Offers lots of value for the money
  • Very simple to use and provides fast results
  • Feels good in the hand and is easy to carry around
  • The app provides lots of practical information for beginners

What Can Be Improved

  • No device screen, you need to use the app to get a reading
  • Unable to pair with more than 1 app 
  • No instructions on how to use it in the box
  • Takes a bit of time to heat up

Keyto is another effective way to measure your metabolism if you want to lose weight with low-carb diets like the keto diet.

The Keyto metabolic tracker measures the acetone levels in your breath and lets you know if you are burning fat or sugar for energy.

It’s designed like a pen that is convenient in size and it feels good in the hand. It weighs only 0.95 ounces (27g), and one battery lasts over 600 breath measurements.

It works as advertised and is actually simple to use. I especially liked how the device also comes with an app and community. 

The app is surprisingly well done, with lots of recipes, great food recommendations, and a helpful plan for the first seven days, including a shopping list. 

  • I don’t like that it takes a bit of time to warm up for each use. Although that’s not a deal breaker overall, as the readings are accurate, and it’s still 10 times faster than urine strips or blood meters when I’m on the go.
  • Another negative aspect is that the device itself cannot show a reading. Instead, you can see it from a mobile device. Yet, thanks to the missing screen, the price is very reasonable.

The keto metabolism measurement package comes with a Keyto device, a carrying case, one AAA battery, and four mouthpieces.

ResultsIn 10 seconds
MethodBreath test
Best forKeto dieters



What We Liked

  • Best metabolism test kit for a clinical setting
  • FDA-registered point-of-care device
  • Offers very accurate readings
  • Device can track the measurements of two users
  • Comes with a screen, so a smartphone isn’t essential for readings

What Can Be Improved

  • Isn’t available for consumers yet
  • Physically bulky, so not a great option when on the go
  • Needs to be calibrated every 14 days for accuracy

The LEVL metabolism monitor measures acetone levels in your breath and tells you how much fat your body is burning per week.

This makes sense when you follow the keto diet and enter ketosis. Then your body produces acetone which can be measured by LEVL.

LEVL metabolic reader is FDA cleared point-of-care device and is highly accurate, and provides readings within 15 seconds.

The metabolic reading results have been tested and validated to 91% of the LEVL measurements were within ± 1.0 ppm of the mass spectrometer. Which is very good..

  • The main negative aspect is that it’s designed for a clinical setting, so we cannot buy it yet as consumers.
  • Another negative aspect for me is that the device needs to be calibrated every 14 days for accuracy. Which is understandable but tedious, especially when there are better alternatives like Lumen or Biosense.

I also liked that LEVL is owned by and made in the U.S.

ResultsIn 10 seconds
MethodBreath test
Best forClinical setting


How to measure metabolism?

The most precise way to measure metabolic rate is with a calorimeter in a laboratory setting, which analyzes your breath rate and tells your resting metabolic rate or basal metabolic rate. It essentially gives you a minimum caloric target but doesn’t tell you if your body is burning fat or not. For this, you can use metabolic trackers like Lumen.

What are the signs of a slow metabolism?

Some common signs of a slow metabolism may include unexpected weight changes, getting tired easily or feeling sluggish, and hair loss. In most cases, excess weight gain has less to do with a “slow” metabolism and more with the increase in calories you eat than the calories your body burns.


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