Lumen Review (2024 Upd.) Does It Work For Weight Loss?

Christiana Mikesch, CPT
Published by Christiana Mikesch, CPT | Senior Coach
Last updated: February 6, 2024
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The Lumen Metabolic Tracker may be useful for health-conscious individuals who wish to be guided on making healthier food choices and engaging in more physical activity.

Over the last five years, the Lumen device and app have been a great investment for me as a fitness trainer in helping my clients understand how their bodies burn fats and carbohydrates to stay healthy.

After spending several months of research, I'd like to share an in-depth Lumen review, so continue reading to understand more about this health device, how it works, and whether or not you actually need it before making an investment in burning fat.

What Is Lumen and Who Is It For?

Lumen Product isolated on a table

Lumen is an electronic metabolism tracker developed by a health and wellness company, Metaflow LTD, for anyone who exercises regularly and wants to measure mostly carbs and fat levels simply by using their breath and finding out whether their body is burning carbohydrates or fat for energy.

Based on first-hand experience, the metabolic measurement it provides can help you adjust your lifestyle, customize your diet, optimize your exercise regimen based on your body’s actual needs, and make decisions that will lead you to your desired goals faster.

More details on how the device works a bit later in this Lumen review.


It’s designed by Israeli twin sisters Michal and Merav Mor, Ironman triathletes, and it may be helpful not only for professional athletes and trainers, but for anyone who exercises regularly and wants to gain insights on how their body works.

For instance, someone who’s already on a paleo diet, keto, low-carb, high-protein, or any other diet but hitting a muscle-building or fat-loss plateau may greatly benefit from the Lumen app's customizable workout and nutrition plan based on each individual's sleeping and eating habits, and specific goals.

You get those guidelines in addition to daily ketone measurements from your breath so that you always know whether you’re in ketosis, i.e. excess fat burning for energy.

I should also say that this gadget isn’t recommended for anyone under 16, obese people, or those with chronic health conditions like asthma, diabetes, COPD, and similar.

Pros and Cons

Lumen helps users achieve their weight loss goals by guiding them to activate their fat burning mode, optimize their respiratory exchange ratio, and enhance their metabolic flexibility, ultimately leading to effective fat burning and successful weight loss.

Here is a quick rundown of the pros and cons of the tracker.

  • High-quality hardware
  • Validated and proven device by San Francisco State University
  • Provides immediate real-time carbs and fat measurement, helping you customize your training goals and nutrition plan as needed without guesswork
  • The app offers plenty of resources to encourage sensible health decisions based on your testing score
  • 30-day money-back guarantee
  • The price may be higher (but it’s cheaper and more convenient than traditional RER metabolic testing or regular glucose and ketone blood tests)

Our #1 Recommended Metabolism Tracker


Rated With Total Shape's Scoring System


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How Does Lumen Work?

Using a lumen product

Lumen works by measuring the concentration of carbon dioxide (CO2) in your breath through an integrated sensor and flow meter that determines whether your body is burning fats or carbs.

Low CO2 levels indicate you’re burning fats, whereas high CO2 levels mean you’re burning mostly carbs for fuel.

Based on the readings, you get personalized recommendations through the Lumen app on workouts, sleep, or nutrition,  like what and when you should eat that day for weight loss, etc.

This at-home tool is said to provide comparable results to the standard clinic measurement of the Respiratory Exchange Ratio (RER) method, which requires much more time and money to test an individual’s metabolic health according to a study posted in the National Library of Medicine [1, 2].

However, the studies claiming this technology is scientifically proven to be accurate are internal and haven’t been peer-reviewed.

Still, other studies from Clinical Nutrition and Metabolic Care, the British Journal of Sports Medicine, and the European Journal of Clinical Nutrition show that similar portable devices are mostly precise and can deliver accurate results, so they deserve closer attention and further research [3, 4, 5].


How Can Lumen Help Improve Your Metabolic Flexibility?

a bunch of girls using lumen metabolism tracker

Lumen can help improve your metabolic flexibility by enabling you to listen to your body, understand it, and make better, personalized workout and eating decisions based on its analysis.

Lumen aims to help you "hack" your metabolic efficiency so that your body can efficiently shift between burning carbs and fats as fuel, or what's called metabolic flexibility. Some practices and habits that can trigger this are exercising, macronutrient manipulation or changing the amounts of carbs, fats, and protein you consume, and time-restricted eating like intermittent fasting.

This metabolic flexibility is measured in the app as Lumen flex score, which ranges from 0 to  21. According to the app's founders, a good Lumen flex score is a sign of improved overall health that can burn fat more effectively, which can also result in the following benefits:

  • Increased energy levels
  • Enhanced physical and mental performance
  • Faster fat loss and lean muscle mass building
  • Better sleep quality
  • Lower risks of metabolic, cardiovascular, and other diseases
  • Improved insulin sensitivity
  • Consistent blood sugar levels
  • Fewer cravings
  • Stronger immune system

Tracking my metabolism with this device through the Flex score has helped me make better food log choices to match the intensity of my workouts. I experienced more energy, a controlled appetite to lose weight and burn fat, and a better sense of well-being, making Lumen worth my time.

How to Use Lumen?

To use Lumen, begin by connecting your device to your smartphone. Within the app, you'll discover comprehensive instructions on accurately measuring your CO2 levels.

You can use Lumen properly by following these steps. I’ve simplified this process and filtered out the most relevant information in the instructions to make it easier to understand.

Step 1: Set-up

The first step is to download the Lumen app on your smartphone, sign up for an account, and connect your device to the app via Bluetooth. (You can log all your data through the app, review the stats, and make adjustments later if you want.)

Then, you answer a few questions about your lifestyle, physiology, health goals, etc. such as your activity level, body composition, sleep pattern, and other similar factors to consider for fat burn and weight loss.

Step 2: Regular Usage

Lumen with different perspective

The Lumen device is generally easy to use, though it can be tricky to get an accurate reading. Through the app, you will get instructions on how to properly measure your CO2 levels.

You need to inhale until a small colored ring on the screen expands to overlap with the outer gray circle. You should immediately stop once the two rings overlap, or else you have to do it all over again.

Then, you will need to remove the device from your mouth, and you should hold your breath for 10 seconds (there will be a timer on the screen), then exhale slow and steadily through the device until the ring on the screen disappears. Make sure to avoid blowing out with too much force so you don't end up with inaccurate results.

Once you succeed at breathing through the device two to three times this way, the app gives you a score of 1 to 5, which tells you whether you’re burning carbs or fat for energy.

We could put the test scores into three groups: 

  • 1 or 2 for a fat-burning state
  • 4 or 5 for running on carbs and
  • 3 for a combination of the two energy sources (both carbs and fats)

It's ideal to use after waking up. If you get a score of 1 or 2, your body burns fats. On the other hand, a score of 4 usually means that your body is still trying to burn what you have eaten the day before.

The app also suggests that you take a breath measurement before a workout to ensure you have enough energy to last throughout the session. This is especially helpful for newbies, but if you're already familiar with how your body reacts to meals and exercise, then this device can confirm your current assumptions.

Based on your morning Lumen metabolism tracker score in the previous few days, the app typically suggests your daily nutrition plan, advising you whether to eat a low-carb, medium-carb, or high-carb diet that day, including the amount of protein, fat, and carbs.

After a month of consistent use, you should be able to see your Lumen score which is equivalent to your metabolic flexibility. This is supposed to show how well your body shifts between burning carbs and fats.

General Tips

a man holding a measuring device in his hands

Here are some general tips clients found useful when using Lumen.

1. Learn To Customize Your Meals

The Lumen metabolism tracker application provides a list of customizable meal suggestions, which comes in handy when you don't have anything planned.

For instance, a Lumen breakfast suggestion may include scrambled tofu, black beans, and a green salad. If you prefer tuna and eggs for breakfast, you can replace the scrambled tofu with boiled eggs and a can of tuna and get nearly the same amount of protein.

2. Plan Your Cheat Meals

The Lumen metabolism tracker makes recommendations for weight loss, such as not eating after 8 p.m. to ensure proper digestion and metabolism over a 12-hour period.

This tip does not necessarily prevent your once-in-a-while desire to indulge in sweet desserts after dinner; however, if you want to see how a specific food affects your body, take measurements one to two hours after your last meal or snack.

3. Learn How Your Exercise Works

The Lumen tracker may recommend exercise routines for your upcoming workout, allowing you to see how each exercise stimulates carbohydrates or burning fat.

This tip may help you understand how different workouts affect your body. And if you want to identify the type of activity that is best suited to your current fitness level, you should take measurements before you begin your workout or half an hour after you finish.

4. Learn How Your Food and Exercise Go Together

Lumen typically recommends a low to moderate carbohydrate intake and, at times, increased carbohydrate consumption after a long, intense training session.

This tip may help you replenish the nutrients lost during physical activity and prepare ahead for a high-carb meal on your grocery list if you intend to work out at a high intensity during your next training session.

For me, I get the best results from taking measurements at least half an hour after I start resting comfortably in a relaxed seated position with a normal pulse and heart rate.

Our #1 Recommended Metabolism Tracker

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Are There Any Negative Side Effects To Using Lumen?

No, there are no negative side effects to using the Lumen. Personally, during my Lumen review, I did not experience any side effects from using it, and based on consumer reviews I found online, Lumen appears to have no serious downsides.

However, some of the app's recommendations can alter your calorie intake when your workout intensities vary, such as recommending a high-carb meal following a strenuous workout.

“The U.S. Dietary Guidelines warns that added sugars may increase the risk of certain chronic diseases. These sugars add unnecessary calories, which can mean body weight gain; some research indicates that added sugars can alter the fat-clearing abilities of the liver, leading to increased blood fat levels and increasing the risk of heart disease.” - Nancy Farrell Allen

RDN, Academy of Nutrition & Dietetics Spokesperson 

I find the device to be effective in monitoring my metabolism, so such suggestions are likely to prove helpful for replenishing nutrients lost after a weight loss workout, but you can always adjust it to meet your specific needs.

Where Can You Buy It?

lumen metabolism trackerYou can buy Lumen from the manufacturer’s official website to ensure that you’ll get a genuine product and be able to take advantage of the discounts, warranty, refund, satisfaction guarantee, and other similar benefits.

When you purchase this handy gadget and open the box, you’ll also find a charging dock, USB-C charging cable, and a travel case in the package.

Plus, you get access to the Lumen App, which is compatible with iOS and Android smartphones, and premium customer support.

All this comes with a 30-day money-back guarantee, a one-year limited warranty, and free US shipping, plus 10% off for ordering two devices.

My order arrived a day ahead of schedule, and I was pleased to receive a genuine, well-packaged device. Also, it included all of the device's accessories.

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Here are some alternatives to Lumen that you may want to consider.

1. Biosense Ketone Monitoring

While Lumen measures CO2 concentration, Biosense measures acetone levels in your breath to determine if you are burning fat or carbs for energy.

Lumen requires an app for reading the results, while Biosense has a screen.

Biosense is best for keto dieters, but I believe it's worth noting that it requires recalibration every six months.

2. MyLab Box At Home Metabolism Test

MyLab Box At Home Metabolism Test is an at-home test that uses finger prick and saliva testing to measure cortisol, testosterone, and thyroid-stimulating hormone.

I've found the expected turnaround time for results is typically within two to five days.

3. KEYTO Breath Sensor

Lumen Metabolism Tracker Reviews

Woman reading Lumen reviews from users

After analyzing testimonials shared online by people using Lumen, I’ve noticed high ratings and 85% of positive reviews with plenty of compliments and very few complaints.

Customers have mainly complained about the lack of integration with other fitness services.

Below are the experiences of some satisfied Lumen users, both individuals and fitness trainers who work with clients.

You may take a look at how this pocket-sized gadget has helped them meet their various goals, from breaking through the plateau and getting leaner to learning how to eat healthier, gaining strength, improving endurance, and many more.

“I’ve been using it for over 2 weeks now and I love that it’s easy to use and provides such great feedback on the habits that negatively affects my metabolism. It motivates me to work harder and better!”


- Kim R.

“Seeing the actual numbers helps me perform and recover at my best. I’m 7 weeks in and my recovery times and energy during workouts have improved a ton. I highly recommend Lumen if you want to be more in touch with your metabolism works.”


- Edgar E.

"I really believe in this product because it's putting out data that's tailored to me, for me to be effective with my clients and their workouts. It's injury prevention and smart training at its finest."

- Troy B.

And here’s how Dr. Molly Maloof reviews Lumen's technology:


Does Lumen Help With Weight Loss?

Yes, Lumen helps with healthy weight loss in a way that it guides you to better fat utilization, helping improve your metabolic flexibility and keeping you motivated to stick to your healthy diet plan.

Can Two People Use the Same Lumen?

No, two people can’t use the same Lumen for fat burn. Theoretically, they can, but it’s neither convenient nor recommended. The device is designed for individual use.

How Much Does Lumen Cost?

Lumen metabolism costs $269; however, the price may not last long. Before you order your device, it’s always better to check the current pricing, discounts, and any available special offers on the official Lumen website.

Is Lumen Safe to Use?

Yes, Lumen is safe to use. It’s just a breath analyzer that helps track your metabolism to achieve your desired goals faster.

Is Lumen Considered A Medical Device?

No, Lumen is not considered a medical device. It is a wellness product that helps you measure, track, analyze, and hack your metabolism. Since it's not a medical advice, it does not provide diagnosis, treatment, or prevention to certain diseases. The recommendations are based on the inputs like carbon dioxide levels and physical activity, and should not be considered as medical advice.

Our Verdict on Lumen

I highly recommend Lumen for active individuals keen on enhancing their wellness. This tool has revolutionized my understanding of how my body burns carbohydrates and fats for energy.

Lumen's standout feature is its ability to tailor weight loss strategies, particularly beneficial for those on a keto diet or seeking to optimize their metabolism.

It's been instrumental in elevating my energy, stamina, mental clarity, and physical performance by aligning my diet with my fitness regime.

If you're committed to transforming your lifestyle, Lumen's personalized nutritional advice and exercise recommendations are invaluable.

Visit Lumen’s website and discover more about harnessing your metabolism.

25$ OFF using code Totalshape

Our #1 Recommended Metabolism Tracker


Rated With Total Shape's Scoring System

  • Sleek design
  • High-quality hardware
  • Portable, handheld, easy-to-charge, and simple-to-use device
  • Provides immediate real-time carbs and fat measurement, helping you customize your training goals and nutrition plan as needed without guesswork
  • Compatible with iOS and Android devices
  • The app offers plenty of resources to encourage sensible health decisions based on your testing score
  • Allows extended fasting
  • Get the BEST PRICE until the end of April
  • The price may be higher (but it’s cheaper and more convenient than traditional RER metabolic testing or regular glucose and ketone blood tests)
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About The Author

Christiana Mikesch, CPT
Senior Coach
Christiana Mikesch, CPT is a personal trainer and author with contributions to publications like the Chicago Tribune and Yahoo. She emphasizes a holistic approach to weight loss, combining an energy-fueling diet, goal-oriented workouts, and daily habits. Her approach avoids short-term goals and fosters a lifelong commitment to health and well-being.
Learn more about our editorial policy
James Cunningham, BSc, CPT
Staff Writer & Senior Coach
James Cunningham, BSc, CPT holds a BSc degree in Sport & Exercise Science from University of Hertfordshire. He's a Health & Performance Coach from London that brings a unique blend of academic knowledge of health supplements and practical exercise experience to the table for his readers.
Learn more about our editorial policy

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