Are you looking to ‘hack your metabolism’ with Lumen? Do you want to get a better grip of your metabolic health to inform your diet and workout? Or perhaps you just want to understand exactly what Lumen is?  Ben Hardman’s Lumen review will cover all the information you need to know about this hand-held, app-based metabolism tracker. 

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Despite using ‘hacking’ – a word I don’t like – I was ready to take Lumen on merit for what it does rather than its marketing spiel.

I’m not going to lie, I was sceptical at first. Very sceptical. A full look into my body’s metabolic habits and wellness from a four-second inhale and six-second exhale? Surely not?

Well, let my honest assessment tell all in my full Lumen review – written after a good month of testing the device.

Quick Verdict: Is Lumen Worth It?

The Lumen Metabolism Tracker gives you powerful knowledge about your own unique metabolism in the palm of your hands. This is a huge advantage for you if you want to know more about how your body is responding to what you’re feeding it – or indeed, what you should be fuelling it with in the first place.

It’s also great for high-performance athletes and fitness enthusiasts who already know their stuff when it comes to nutrition, but want to unlock that extra level in training demands and results.

The Lumen is easy to use, although you’ll need to be committed to opening the app each time to have your breath analysed. The app is user friendly, although you do need to manually input some data, which again takes commitment from you.

The product itself is stylish and neat – we love how it looks and feels.

The Lumen, we think, is at a price well justified – it’s down to the user how much they take advantage of the knowledge it provides, and whether they can put it to good use.

About This Lumen Review 

One of the perks of writing for a health and fitness online publication is that you sometimes get offered the chance to test something you otherwise wouldn’t.

That’s the offer I got with Lumen.

Like a lot of devices on the market, Lumen is aiming to combine health and fitness with technology to improve metabolic flexibility (we’ll get onto this shortly), general health and energy

And in truth, it’s a good match. I’m interested in nutrition, I work out at the gym, I track my sleep and I occasionally track my macros when I think I’m not eating intuitively or cutting for an event. I’m also into my technology, although nowhere near as much as some people.

Would I have actively gone out looking for a way to track and manipulate my metabolism though? Probably not. 

Was I interested in finding out whether it works, and was I willing to test it out? Absolutely. 

So I spent six weeks testing the handheld Lumen device with the accompanying Lumen app. By the end of this review you will have a good idea about how Lumen works, how accurate it is, how it will make you feel and, ultimately, if it is a good addition to your daily health and fitness regime.

Lumen Metabolism Tracker Overview

The Lumen Metabolism Tracker is a unique, handheld biotechnology device. Its main aim is to provide insights into how your body utilises carbohydrates and fats for energy

This innovative gadget operates by analysing your breath. Sounds a bit weird, but you can get a lot from your breath, which I haven’t really thought about before. This includes an indication of your metabolic state, plus metabolic flexibility over time. Clever.

By simply breathing into the device, the technology inside the Lumen can determine if you’re burning carbohydrates or fats to provide your body with energy

All the data goes into the Lumen app on your smartphone device. This is the hub of this technology – you can’t use Lumen without the app.  

From your metabolic data, Lumen offers personalised recommendations and health insights. For example, it uses the data to suggest how you can optimise your diet and exercise regime. The overall aim is to improve your metabolic flexibility, help weight management efforts and enhance overall health.

The main concern for most potential users is the price. It’s not cheap and should be seen as more of an investment. But is this investment worth it? 

In my opinion, it’s worth the investment if you’re not fully versed and in sync with how your diet is affecting your health. From this perspective, it’s more suitable for people at the beginning to middle stages of their fitness journey. However, it’s also been suggested that Lumen can be useful for top-performing athletes who are tracking all health-related matters to eek out a percentage or two more from their performance. 

Personally, I feel like I’ve got a good handle on how my diet impacts my metabolism. Not perfect by any means, but good enough without going to the next level of tracking. 

I’ve enjoyed using Lumen and found it very interesting. Using the device has certainly made me more aware of my diet-metabolism connection, rather than just diet in relation to protein intake or body weight. 

That said, a metabolism tracker is not something I see myself using every day. I’d rather spend the money on new supplements or lifting shoes, but that’s just me. 

However, if you’re looking to gain a deeper understanding of your metabolism and improve your health through tailored recommendations, this innovative gadget may be a worthwhile addition to your fitness arsenal.

Lumen – Out Of The Box 

Everything about Lumen feels premium. 

This all starts with the packaging. When you get your Lumen delivery, you could be forgiven for thinking you have just received the latest iteration of the iPhone. The packaging and presentation are slick and the styling is minimalist – all very Apple and all very lovely. 

In the box is your:

  • Lumen handheld device
  • Carry bag for your Lumen (which is really handy)
  • Charging stand with USB Type C cable to power it 
  • Welcome pack that explains the basics and includes your warranty

The device itself has a really top-end feel to it. It’s solid, has a good weight to it (but isn’t too heavy), and has a nice, matte feel. 

My Lumen actually got mistaken for a vape by my partner when she saw it on the side. It has a resemblance to this sort of device, but the Lumen is way better. 

The device has a metal cap that covers the metal mouthpiece you breathe in and out through. I like the metallic element to Lumen. In good attention to detail, they’ve also made the cap and mouth piece magnetic, so it fits very securely into place. 

At the bottom of the device, there’s a button to switch the device on. Once clicked, a ring lights up in the middle of the device to indicate it’s been switched on.

The handheld Lumen sits in its charging dock, which is also nicely made. It again has a sturdy weight to it and a rubber ring on the bottom to stop it sliding about or scratching your table. Be careful not to knock the Lumen when it’s in the charging stand as it will fall over. The groove it sits in is only shallow and it’s not magnetised into place, which makes it vulnerable to wobbling over. 

The Lumen can be used on the go, but I personally kept it stationed in its charging dock.

Overall though, the Lumen really is a well thought-out and stylish piece of kit. Top marks from me.

How Lumen Works

Using Lumen is very simple. Each time you track your metabolism, you go through an easy three-stage process:

  1. Breathe in through the device for 4 seconds.
  2. Hold your breath for 10 seconds (away from the device).
  3. Breathe out through the device for 10 seconds.

This is how you use the device on its own. However, before you do your inhale and exhale, you need to make sure your handheld Lumen is connected to the Lumen app on your phone before you use it. This is so the data from your breath can be analysed and visualised to you.

Although very good, it’s a slight downside that the Lumen device can’t be used outright on its own. Instead, when you want to track your metabolism, you must open the app on your phone and then turn on the Lumen. My iPhone paired usually within 1-2 seconds, with not once a connection issue – which tells us the tech and software is good.

With the app and Lumen paired, you click the little breath icon on the app and it will talk you through the entire process. 

The app uses illustrations, audio and text to show you exactly what to do. There is a visual indicator to make sure you are not breathing in or out too fast or too slowly, with the aim being to keep a ball in the middle of a circle. I found this useful.

What Is Lumen Measuring?

Ok, we’ve got the breathwork technique, but what’s the Lumen tracker actually measuring? 

In order to determine what fuel source your body is currently using (fats or carbs), the Lumen measures carbon dioxide (CO2) levels in your breath to calculate your respiratory exchange ratio (RER).

Your RER is an industry-leading method (which is also scientifically validated) to determine your body’s main energy source at that given moment. The ratio is between the oxygen you breathe in versus the amount of CO2 you breathe out. 

The technology that sits behind the scenes is vital for this device. Your breath will get a read-out and this will be assigned a Lumen level. Based on your RER, there are five Lumen levels you can be given:

  • Level 1: Burning fat for energy (80-100% fat)
  • Level 2: Burning mostly fat for energy (60-80% fat) 
  • Level 3: Burning both fats and carbs for energy (40-60% fat)
  • Level 4: Burning mostly carbs for energy (60-80% carbs)
  • Level 5: Burning carbs for energy (80-100% carbs)

Most of my breaths were given a level 3, but there were a couple of level 4s in there, plus a few level 2s when I was cutting my calories down. 

It’s only after 4 weeks of consistent breath measurements and nutrition tracking that Lumen will assign you a ‘flex score‘. This flex score tells you how metabolically flexible you are. Although interesting to know, on its own the flex score is rather pointless. It’s what you do with this info that’s crucial. 

Understanding more about your metabolism allows you to make wiser nutritional choices on a daily basis. Improving your nutritional choices will give you more energy, increase your mood, help improve your sleep and even allow you to burn more fat. 

Let’s lean into the science behind Lumen a little more.

The Science Behind Lumen

Metabolism is a complex process that involves the conversion of the food we consume into energy. Essentially, metabolism is what helps all living organisms to stay alive. 

For humans, metabolism plays a crucial role in regulating body weight and energy levels. The efficiency of an individual’s metabolism can be influenced by factors such as age, gender, genetics, and lifestyle habits. So, understanding your metabolism is important for better overall health. 

The Lumen metabolism tracker is a device designed to help users better understand their metabolism by analysing the gases in their breath. It’s like a metabolism breathalyser. The tracker works by measuring the concentration of carbon dioxide in your breath. 

This information is used to determine how effectively the body is burning carbohydrates or fats for energy. When the body burns carbohydrates, it produces more CO2 compared to when it uses fats. By analysing the CO2 levels, Lumen can estimate if you’re in a carb-burning or fat-burning state.

Over time, you’ll be given a metabolic flexibility score. The aim is to be more metabolically flexible. Increasing your metabolic flexibility brings advantages to mitochondrial functioning as well as insulin sensitivity, helping to partition carbs into muscles rather than get stored as fat. 

The benefit of metabolic flexibility for your body goes back to when humans were evolving. Early humans living from the land would need to use carbs and fats interchangeably to fuel activity. This was when you couldn’t just pop to your fridge, the shop or order a delivery on your phone.

How Accurate Is Lumen?

Lumen is accurate. 

The device has been tested, scientifically validated and peer reviewed. 

Previously, the only way to test your own metabolism would be at a clinic or in a hospital. Lumen states that their device has comparable results to lab-based RER measurements. These results aren’t 100% accurate, but they’re very much in the same area. So, it’s good to know that your metabolism can be accurately tracked at home.

The Lumen device can achieve this due to its sleek internal design that holds a flow channel, CO2 sensor and flow metre. After an initial use to set up, the device is calibrated to your unique CO2 range and lung capacity.  

Alongside the well-established RER method for estimating metabolic rates, Lumen uses its own algorithm to determine your full metabolic activity.

Data and Information From Your Lumen Device

From your breath alone, the Lumen device gives you a whole host of information. Here’s a snapshot of the Lumen insights.

Real-Time Metabolism Tracking

Lumen’s metabolic breath analyser provides real-time insights into your metabolism. 

By breathing into the device, users can determine whether their body is using carbohydrates or fat for fuel. This information can be useful for making healthier choices and adapting your diet or exercise routine to reach personal fitness goals.

Nutrition Recommendations

Based on your metabolism data, Lumen also offers personalised nutrition recommendations to help improve your overall metabolic health i.e. your metabolic flexibility. 

The nutrition suggestions are tailored to your unique metabolic profile, providing a more targeted approach to diet and nutrition than the more general guidelines offered by other health trackers.

If you want further insights with Lumen, you do have to manually input all of the food you’ve eaten each day.  

Activity Suggestions

In addition to nutrition, Lumen also provides useful activity recommendations to help you achieve your fitness goals. By analysing your metabolism, Lumen can suggest appropriate exercise routines for either fat burning or muscle building. 

The guidance is designed to enhance overall metabolic health and improve physical performance.

Progress Monitoring

Using the Lumen tracker over the long term allows you to monitor your metabolic activity over time. 

The device tracks the changes in your metabolism, nutrition and activity levels, which then improve the effectiveness of the tailored recommendations provided by Lumen. 

With regular daily use, users can see a visual representation of their progress. This adds an extra motivational factor – when you can visually see the difference in your levels, you feel more driven to make positive changes to keep those visuals on the positive, thus actively improving your overall health.

The Lumen App 

Everything to do with Lumen is centred around the Lumen App. It’s here where you assist with your breath measurements and it’s also where you get to see all the real-time data. However, there is far more to the app than just that. 

The app features useful welcome video guides, with each short video explaining everything from how to measure to when to measure, how to count your carbs and how to stay committed to the cause. 

You can log your workouts and your nutrition, add your current weight, and see all of your stats. There is an Explore section that contains even more media around eating, nutrition and weight loss, and there are some quick links to recipes and even a ready-made meal prep service. 

App Layout and Experience

I found the app to be quite user friendly once I’d been using it for a week or so. The visuals are good and all relevant data is presented in an easy-to-digest manner. 

The app features four main sections at the bottom:

  • Today – Allows you to measure your breath, shows you a snippet of your nutrition plan and daily goals, allows you to add a workout, and gives you an overview of your week so far.
  • Nutrition – Allows you to track and plan your food. Track is where you log everything and can add meals. You can save certain food combos to speed this up. It also gives you an overview of the macros for the day. The Plan section of Nutrition allows you to alter your macros, plus gives you lots of ideas and recipes to try out.
  • Explore – The Explore tab has different video collections and articles to keep you motivated, educated and inspired.
  • Me – Finally, the Me tab is all about you, of course. It has all of your stats, progress charts and flex score.

Integration with Other Fitness Trackers

One of the advantages of the Lumen metabolism tracker is its ability to integrate with popular fitness apps like Apple Health and Motion & Fitness. You can also sync Lumen with your Garmin account if you have a Garmin device. 

From sleep trackers to activity data, integrating with other platforms and devices is a great idea to provide a comprehensive overview on health and well-being.

I personally don’t use Apple Health, but I’ve read that it syncs up well. 

I think the integration with fitness apps could be improved by adding more popular trackers such as My Fitness Pal, so you don’t have to start again with manually inputting food sources.

Pros and Cons of Lumen Metabolism Tracker

As with any product, the Lumen metabolism tracker has both its advantages and drawbacks. Let’s assess them both.


  1. Easy set-up: Once you’ve downloaded the Lumen app, it’s a case of connecting the device via Bluetooth to your smartphone and answering a short quiz to give Lumen a baseline of your health. 
  2. Easy to use: Once you’re all set up, the device is really easy to use. Just click the breath icon, listen to the instructions and take a measurement. Job done.
  3. Clear and concise app: The Lumen app provides clear insights into your metabolism and helps you make informed decisions about diet and exercise habits.
  4. Accurate readings: The handheld device gives comparable metabolic insights to lab-based tests.
  5. Quality hardware: The breathalyser device hardware is simple, sleek, and of premium quality. The charging dock is good quality too.


  1. Expensive: One common concern about the Lumen metabolism tracker is its cost. When you buy a Lumen device it comes with a 6-month or 12-month paid subscription. Although it is expensive, you’re getting personal insights that you could only previously get in a clinic or hospital.  
  2. Requires commitment: To get the most out of the Lumen tracker, you need to use it everyday. This isn’t difficult to do, but it means you’re committed for the long term if you want to get the best results.
  3. Manual data input: Users are required to input some data manually, such as food intake for the day. This can be time-consuming, but you can also save food choices for easy input next time.
  4. Smartphone requirements: You can’t analyse your breath without being connected to the Lumen app. It would be good if you could record a breath, then connect it to your phone at a later point and have the results uploaded. This would make me use it more often throughout the day, rather than just in the morning.

Overall, the Lumen metabolism tracker does have its pros and cons. Whether the pros outweigh the cons depends on the individual. For those dedicated to improving their metabolic health and flexibility, the Lumen is a great little device.

Who Would Benefit From Using Lumen?

The Lumen metabolism tracker device is likely to benefit several types of individuals.

Firstly, those trying to lose weight or maintain their current weight could find Lumen particularly valuable. By analysing breath to determine carbon dioxide levels, the device allows users to track their metabolism in real time and provides personalised nutrition recommendations based on the data.

For people who aren’t accustomed to accurately planning their nutrition, tracking macros, and following a training regime, Lumen can be a good first step onto the ladder. The benefit of using Lumen for beginners is that it can help you make better choices for optimising nutrient intake and supporting weight management goals.

Additionally, fitness enthusiasts and athletes looking to improve their performance can benefit from Lumen. The insights provided by the device can help optimise training and recovery by identifying the most favourable fuel source for the body during specific workouts or at different times of the day. Armed with this info, an individual can adapt their nutrition plan to meet their training demands and achieve better results.

I’d put myself in the fitness enthusiast camp, but I don’t think I’ll be using Lumen over the long term. This isn’t because the device is poor or inaccurate – on the contrary, it’s very good – but I felt that I didn’t fully need the extra information being provided to aid my training and lifestyle.

Don’t get me wrong, it was interesting to track my metabolism for a while, but I don’t think that it significantly affected my lifestyle choices anymore than I would change on my own.

Lastly, for those simply interested in understanding their body and metabolism on a deeper level, Lumen could be a useful tool. By providing information on individual metabolism and daily fluctuations, the device can help users adopt a more personalised approach to their diet and lifestyle choices.

It’s true that Lumen can benefit a wide range of individuals – those seeking to gain better control of weight management, those wanting improved athletic performance, and those wanting a deeper understanding of their body’s metabolism.

Who’s behind the Lumen metabolism tracker?

The Lumen metabolism tracker is a product by Meta Flow Ltd., a US-based health technology company.

Lumen was founded by twin sisters Merav and Michal Mor. Both are Ironman winners and both hold PhDs. Their unique experiences as scientists and athletes are what inspired them to create Lumen. 

The sisters teamed up with Daniel Tal Mor (CEO), Dror Ceder (Chief Growth Officer) and Avi Smila (CTO) to develop the first Lumen prototype after two years of research and development. Their collective expertise has resulted in the development of the Lumen device and its underlying technology.

The team behind Lumen believe that understanding your metabolism is a key factor in achieving personal health and fitness goals.

The Lumen metabolism tracker was designed to achieve this goal by offering users real-time information and personalised recommendations based on their unique metabolic profile. 

This innovative approach not only helps people understand how their own body responds to different types of food and physical activity, but also offers guidance on making healthy lifestyle choices that are tailored to their needs.

The breath analysis technology used within Lumen was developed over the course of four years, involving thousands of users taking part in beta trials. Clearly, much work, experiences, research and commitment went into delivering us the Lumen and its incredible biotechnology.

Final verdict on Lumen

The Lumen metabolism tracker is without doubt a unique and innovative device. It’s the only handheld, portable biotechnology device on the market that allows users to measure and track their metabolism with ease and convenience.

It has gained mostly positive reviews since its launch. I’d say that this review is a positive one for Lumen’s collection, too. 

The device comes with a premium build and easy-to-use app software, and accurately goes about its purpose – to measure your metabolism. 

The overall premise of the device is to encourage users towards a healthier lifestyle. It does this by primarily targeting metabolic health and flexibility, but achieving this also has the double benefit of impacting overall health, well-being and mood. I’m a fan of anything that helps these points. 

I also think garnering a deeper understanding of metabolism is important for a lot of people who are often in the dark about this aspect of their body.

And with that in mind, the Lumen tracker is a top-quality, innovative product. Whether or not it’s a product for you depends on your individual goals and needs.