Lumen Review – 2024

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Last Updated: January 5, 2024

Have you ever wanted to know how effective your metabolism is? How does it process the foods you eat? Well, the Lumen might be able to give you some answers and insight into how flexible your metabolism is. “Flexible” is what Lumen describes as an efficient metabolism and using the Lumen device is said to help you improve your metabolism and teach your body to use specific types of foods for energy. This all sounds great, right? But is it too good to be true? I tried Lumen for four months (and continue to use it) to see if it does what it claims and if it’s worth it. In this Lumen review, I’ll go over my experience and what you should know.

This small, handheld device is only part of what Lumen has to offer.

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What Is Lumen?

Lumen is a small, handheld device that you breathe into. The device connects through Bluetooth to the Lumen app to read your breath to determine if you are burning fat, carbs, or a combination of the two. The Lumen does this by reading the Co2 levels in your breath. RER (respiratory exchange ratio) is the ratio of carbon dioxide and oxygen that your body is producing at any given moment. RER is used to measure a person’s metabolism in clinical settings. Check out this article to learn more about the effectiveness and validation of Lumen compared to a machine that measures RER in a laboratory setting.

With this information, Lumen creates a nutrition plan to encourage your metabolism to become more flexible, therefore “hacking your metabolism”. Think: building muscle and shedding fat – the dream, right? Or not crashing during the marathon portion of your Ironman Triathlon- which was the initial idea behind Lumen from its founders, sisters, and Ironman winners: Merav and Michal Mor.

Essentially, the idea is to train your body to switch between using carbohydrates and fat for energy depending on the food you eat, time of day, and activity. With increased metabolic flexibility, Lumen claims users will have better sleep and athletic performance and will be able to lose weight more easily (if that is your goal).

Why You Should Trust Our Review Of Lumen

In addition to extensive experience testing and reviewing all kinds of fitness products, our reviewers are knowledgeable and experienced with the other important factor that goes into health and overall fitness: nutrition. Our team consists of certified sports nutritionists, such as myself, as well as health enthusiasts who value nutrition just as highly as we value fitness. For this review, some of our team members received a Lumen each to use, and this review reflects all of our experiences using it.

In-depth Review Of Lumen

Lumen App

First and foremost when you purchase a Lumen, you’re purchasing a membership, which is a subscription to use the Lumen App, as well as the Lumen device. There is the option to purchase a 6 or 12-month membership to start. This is required and necessary to use all of the features in the app and the device. Without the app and connection to wifi/service on your phone when using the device, it is useless.

Wherever my phone goes the Lumen goes, nowadays.

The app is where you’ll get your Lumen level readings. This is what tells you if you’re burning primarily fat, carbs, or both when you breathe into the device. The Lumen app is also where you get your personalized nutrition plan, and log important factors like your food and sleep. You can connect to apps like the Apple Health App for tracking your sleep and exercise, which is very convenient. The Lumen app is where you’ll also receive your Flex Score (more on this later).

When you sign up for Lumen, you will create a profile with information like your height, weight, age, and track. The track is what your goal is with using Lumen. The tracks available are Metabolic Health (maintaining weight but improving metabolic health), Healthy Weight Loss, and Fitness Performance. For this review, I chose the healthy weight loss track. I figured this would be the easiest way for me to see if the Lumen actually works.

Lumen Levels

When you use the small handheld Lumen device, you’ll take a breath into it, hold your breath, and then exhale through it, like a breathalyzer. There is a prompt in the app that guides you through this process every time you use the device to measure your metabolism. It can take some getting used to, in order to breathe the way Lumen instructs you to, but this gets easier the more you use Lumen.

The prompt guides you to get the green dot in the circle when you’re inhaling and exhaling and the ring fills with color around the dot as you breathe.

In order to do a measurement, the Lumen will ask you to log the reason why you’re checking your metabolism. The options are morning (when you first wake up), before exercise, after exercise, before eating, after eating, after fasting, before sleeping, and a custom check-in. Lumen considers these as tags so you can track how your metabolism responds to specific things like meals, exercise, and sleep.

With all of those options to choose from you might be wondering how often you actually use the Lumen device. Well, in short, a lot. The morning and before sleeping measurements are said to be the most important because they’re reflections of how your body responds to your daily and nightly habits. However, if you want to get the most out of Lumen, you’ll need to do your metabolism measurement often. Before and after meals, every morning upon waking, every night before bed, and before and after exercise. This way you can see how specific foods, your sleep, and even forms of exercise affect your metabolism.

So, when you breathe into the Lumen, after picking the appropriate tag, the device analyses the amount of Co2 in your breath and gives you insight into what your body is using for fuel. This is shown on a range of 1-5. 1 and 2 mean you’re primarily burning fat, 3 means you’re burning both fat and carbs, and 4 and 5 mean you’re burning primarily carbs.

The app will tell you exactly what your level is for every reading and save your readings in the app.

The idea is that you want your body to burn fat for fuel when it’s at rest and burn carbs when you consume carbs and when you’re active. The goal is to have a 1-2 in the morning after sleeping, and 3-5 after consuming carbs and before moderate to high levels of exercise, to ensure you’re properly fueled with energy.

Flex Score

After the first 2 weeks of using Lumen, you’ll receive your first flex score. This is a score of how flexible your metabolism is. The idea of having a flexible metabolism is that your body efficiently uses the carbohydrates you give it for energy rather than storing the carbs as fat. Carbs are our bodies primary source of energy, so when we consume them we want our bodies to use them efficiently.

Lumen’s flex score is on a scale of 0-21. 0-6 indicates your metabolism has low flexibility, 7-14 is medium flexibility, and 15-21 is high flexibility and ultimately what you want. Every Monday you receive a new score which can help indicate if you’re progressing or not.

Nutrition Plan

While you can use the Lumen without following the nutrition plan that is created for you in the app, you probably won’t see as many (if any) results. A large part of what affects your readings and your metabolism is what you eat. Stress and sleep quality are also significant factors, but food is incredibly important and at least for me the easiest to control and change (for the most part – I’ve never met a burger and fries combo that I didn’t like).

Lumen utilizes macronutrient tracking. Food is split into three macronutrients: protein, carbs, and fat. These are all essential nutrients our bodies need to survive. Water, vitamins, and minerals are the other essential nutrients we need. I wish Lumen had a log for daily water intake, but it has a meal log that is divided into specific daily goals for your protein, carbs, and fats. Once you add foods/meals into the log, you’ll see your total calories for the day.

The macro tracker is pretty easy to use to log your food. This is my tracker after logging my breakfast and lunch only. Keep in mind that everyone’s macro goals will be different, and they are calculated based on factors like height, weight, and activity level.

My protein goal remains pretty much the same every day. It is calculated to be around 0.8 – 1 gram of protein per pound of body weight. This is consistent with other macro trackers that I’ve used for weight loss. This calculation might be different depending on which track you pick and the goals you have with Lumen. The daily goal for fat and carbs ranges from day to day with Lumen’s nutrition plan.

In order to teach your metabolism to become more flexible, Lumen uses carb-cycling. Some days you’ll have low-carb goals and higher fat, and other days you’ll have higher carbs and lower-fat goals. As soon as you do your morning measurement, Lumen will determine if it’s a low, medium, or high-carb day. You’ll also get a boost day, which is a very high level of carbs to consume. I struggle to meet my carb goal these days.

Because your macros (except protein) change from day to day, meal planning can be challenging. However, if you improve your metabolic flexibility and get low Lumen levels consistently in the morning, you will have a good idea of which days will be low-carb or boost days. If you wake up with a high Lumen level (3-5) you will have a low-carb day. If you’ve blown a 1-2 in the morning for 4 days in a row, the 4th day will be a boost day. If you perform moderate to high-intensity exercise, your carb amount will increase for the day to ensure you are properly fueled with carbs for your workout. Without proper carb stores, your body can resort to breaking down muscle for energy, which is not what you want.

As soon as you do your morning reading, a banner a the top of the home screen will tell you what kind of carb day it is.

Now, I’ve done macro tracking in the past and have calculated my own macronutrient ratio, so this wasn’t foreign to me. Macro tracking can be a great tool for weight loss, body recomposition, and even just gaining insight into what you’re consuming every day. It might not be best for those who suffer from disordered eating, such as eating disorders, or restrictive or compulsive eating. If you’re someone who gets hyper-fixated on calorie counting, Lumen might not be a great option for you. Keep in mind that I’m NOT a medical professional, but with my experience using Lumen, I’ve noticed that following the nutrition plan isn’t the healthiest option for everyone.

Construction Quality / Durability

The Lumen device is small. It fits in the palm of my hand. Every person who has seen me use it thinks it is a vape because it looks like one. We even have a running joke in the office that it’s time for me to vape – if you met me you would know that I’m the last person to pick up the habit.

But yes, the Lumen does resemble a vape. It’s compact to take with me anywhere (I’ve even taken it on a flight in my carry-on without any problems). I can fit it in my little fanny-pack, or in my coat pocket. The Lumen comes with a soft zipper case for transporting.

The Lumen device comes with a charging station, carrying case, and mouthpiece cap.

We’re impressed with the overall construction of the Lumen. It feels solid and nice in your hands. The Lumen comes with a hard cap for the mouthpiece to keep dirt and debris from getting in there. The cap seems to have a little magnet in it so it remains on the mouthpiece, too. This is a nice touch.

You might be thinking how sanitary can the device be if you’re breathing into it 1-10+ times a day? I had the same thought. There are sensors that heat up to kill any bacteria. Although, the Lumen never feels warm when being used. Trust me, I would let you know if there was anything funky growing in mine.

At the bottom of the device, you can see a light flashing inside when it is on.

When you press the small “on” button, a ring appears. When it’s white it means it’s on but not connected to the Lumen app. A purple ring means the device is connected to the app. When you have it on the included charging port, the ring will be green once it is fully charged. The Lumen powers off after not being used for a few minutes.

Performance & Functionality

A big takeaway that we’ve gotten from using Lumen is that it is intensive. In order to see results, you must put in the work. Compared to diets and macro tracking that I’ve done in the past, the Lumen is a bit more time-consuming. It requires some preparation, such as making sure the Lumen is nearby you before bed for your morning measurements, and on the go with you for meals out of the house. You also have to remember to use it. Lumen can help with this if you set notifications in the app, but these only go so far, in my experience. A timer on your phone might help with remembering.

I like to think of the Lumen as an accountabilibuddy. By measuring your metabolism (sometimes upwards of 10 times a day) and following and tracking your nutrition, you definitely feel accountable. For me, it’s one thing to track my food, it’s another to see how that food is impacting my metabolism.

So, did the Lumen work for me? Yes, it did. It also worked for our reviewers when they would follow the nutrition plan and regularly do measurements. However, we quickly found that Lumen isn’t for everyone, including some of our reviewers, because of how time-consuming it is.

Matthew saw success from Lumen when he used it, too.

I lost about 3-5 lbs using Lumen, which might not seem like much, especially over the course of 4 months. Unfortunately, I did get Covid a few months into using the Lumen and that definitely derailed my progress.

I’m a fairly healthy person. Sure, there are areas of my diet that need improvement from time to time. I’m not always the best at getting in my daily vegetables, and hitting my protein goal definitely requires some effort. By using the Lumen, I’ve been able to see what kind of exercise and carbs are best for me. For instance, for low to medium-intensity workouts, I don’t need to fuel up with carbs before. This type of exercise for me usually is walking and strength training. Running and other forms of cardio, on the other hand, are best if I have some carbs beforehand.

I was pleased to get a high flexibility score after my first two weeks of using Lumen. For the next two months, I was able to maintain and increase my score, shed a couple of pounds, and get the hang of Lumen, until I got sick. Besides food consumption, stress and sleep are other factors that can influence your daily measurements and your flex score. Getting sick is definitely a stressor on your body and my daily measurements soon started to reflect how I was feeling.

I consistently blew 3-5’s with every measurement for around the following month or so. This is about as long as my lingering cough lasted after the infection. So, the Lumen not only is a reflection of what you’re eating but your lifestyle and how you’re feeling, as well. If you are stressed or having poor sleep, the Lumen will pick up on that. Most people will probably see a rise in their Lumen numbers since our bodies tend to burn carbs when stressed, but keep in mind that we’re all different.

I will admit that since getting sick and derailing my progress, I haven’t been able to get to where I was yet. I also haven’t been following my Lumen nutrition plan as closely as I was before (or at all), So, like Taylor Swift says, “Hi, it’s me. I’m the problem. It’s me.” Even though I’m still using Lumen every day and tracking my food, I’m not seeing results because I’m not putting in the work. And if you’re not willing to put in the work, Lumen won’t work.

Lumen of course won’t work for everyone and Lumen isn’t recommended for those with diabetes, asthma, COPD, and if you’re pregnant. Our team also doesn’t recommend Lumen if you don’t like tracking your food and having to take measurements throughout the day.

If you want insight into how your lifestyle affects your metabolism and want to improve your metabolism (and if you don’t mind tracking food), Lumen is a great tool to help you do so.

Warranty & Customer Service

The Lumen device is under warranty as long as you have an active subscription. So, if your device becomes faulty, the warranty will cover it. It won’t cover it if you accidentally damage the device, though.

As far as customer service, I am blown away by how much information and guidance Lumen gives you in the app. There are educational videos and webinars you’ll have access to, as well as a Lumen Facebook group filled with other members. Some of the questions others ask in the Facebook group have been very helpful. Plus, one of Lumen’s support members usually answers the questions in the Facebook group. Lumen has been an insightful learning experience, and the resources and help from the company itself are wonderful.

Plus, there are nutritionists in the app that you can chat with, for any questions you have. I’ve had questions during my time using Lumen so far, and the in-app chat has been extremely helpful. For one, they’re actual people in the chat, and knowledgable to boot!