I was a bit skeptical about the Lumen metabolism tracker device but after about 1 week of use I have found it to be a very useful and promising device for weight loss and/or weight management - I even lost a couple pounds during my first week of use. I love that the app determines your daily macro intake based on your breath measurements and provides suggested meal options as an added bonus. I don't know enough about the science of the Lumen device, but, for me, the breath measurements collected seemed accurate. Additionally, the real time data from the daily measurements boosted my motivation to put in the work each day to meet macro goals. (It was almost like a game to me.) Typically any adjustments to eating habits is tracked by weight loss which doesn't provide instant results to gauge your progress. The measurements taken with the Lumen device allows users to see how their body (metabolism) responds to various situations throughout the day, providing real time results, with a primary focus around meals, workouts, fasting, and your sleep. The device is very easy to use and the Lumen app, after some use, is simple to navigate as well. Another great feature of the app is that it allows for one to connect or sync many health tracking apps. Unfortunately Samsung is not one that can be linked, which is what I use, and that was very disappointing considering that it is a major brand. Most of my experience using the Lumen app went smoothly, but it was a bit buggy at times. There were several times that the search feature for logging meals would freeze and that often resulted in me having to restart the app. There were also a couple days that outages within Google seemed to really affect the functionality of the app too. The barcode scanner for logging meals was surprisingly quick and accurate, and I did try to utilize that often. I was also pleased with the amount of food items already included within the database as well. There are many features with the app that should satisfy most users’ needs. Between the numerous features and the personalized plans the membership fee seems very reasonable. Overall, I have been mostly impressed with the Lumen device and its app. For those looking to try something different, or for those who need more instantaneous progress feedback, the Lumen metabolism tracker just might be the missing piece in your health journey.

A few years ago, I was diagnosed with Type-2 Diabetes. Fortunately, I’ve been able to manage it quite well by limiting sugar intake along with medications. Since I’ve gotten the A1C level in check, the next step in my health journey is to lose some weight. While the Lumen is not marketed as a weight loss device, my hope is that it will help me with carb awareness and help to encourage me towards better eating habits for the long term. The Lumen device is a very premium-looking piece of technology. It comes in an impressive black box and comes with its own charging stand and travel pouch. The app for Lumen is quite nice, too. Downloading it is the first step in setting it up. The app will guide you through the set up process and train you in how to measure your breath with the device. Lumen does require a subscription ($19/month or $180/year) for ongoing use, but it comes with one month free with the purchase. In a world that seems to have a subscription for nearly everything, I wasn’t surprised about this added expense, but it was disappointing. Since this is a health-tracking device, I would put it in a similar category to something like a gym membership, which requires a monthly fee, but I think it could be lowered quite a bit. As a means of comparison, I’m able to monitor my glucose and track it through an app without an recurring fee. I did have to purchase my glucose monitor, but the app came with no strings attached. So, while I accept there is an ongoing fee for this type of system, I think the cost could be lowered. Using it in practice is somewhat of a feat. First of all, you have to discipline yourself to use it the same time everyday. While having this sort of requirement is helpful for forming good habits, it’s still a hurdle to overcome. Second, the breath capturing process is a little different than I expected. You have to take a slow breath in, hold it for ten seconds, and then exhale slowly. This could be very difficult for some people who have breathing deficiencies. I found it a little difficult at first because the app guides you not to do it to fast or hard. It gives you an on-screen prompt and tells you to keep the ball inside a certain perimeter while you are completing your breathing exercise. It took me a couple of tries to get it just right. So, like I said, discipline is key with this device. For me, I was using Lumen as a supplemental device to help kick start weight loss and monitor my carb burning. I feel that it is helping by providing more information to me, but I question how accurate it is since you have to do the testing ‘just right’ every time you do it. Plus, I was expecting information that was more specific than simply burning fat or carbs. That said, I could see Lumen being very useful for people because the full benefit comes from committing to the daily routines and guidance, not just using the device. Pros: Easy to use Device feels premium App guides your habits Can help drive smarter decisions if you’re looking to optimize energy levels, fat burning, or diet timing. Cons: Requires discipline to make sure you are doing it the same time everyday at the right times for accuracy Device gives you a ‘rough estimate’ of fuel usage, but it’s not as precise as clinical testing (can’t replace that) Not a ‘magic bullet’ for weight loss - could confuse some people expecting that

PROS: * Very nice quality * Robust app (so many links, videos, stats, and data) * syncs with other health services (i.e. Apple Fit, Fitbit, Garmin) * Easy to use * Comes with an included travel case CONS: * Another subscription service ($19/month or $180/year) * May not separate itself from other smart wearables enough for some If you've come across this product, you might be wondering what it does. I certainly was. According to Lumen, they've created this device to help people improve their metabolic flexibility, which can lead to better workouts, improved sleep, easier weight loss, and an overall happier, longer life. While this may or may not appeal to you, it certainly appeals to me. As a tech lover, I've found that as I age, it takes more effort to maintain my health (I wish it were the other way around). Sleep has always been a challenging aspect for me to manage consistently, so anything that can help me improve my routine is a welcome addition. So far, using the Lumen device has made me more aware of what I eat, how much I move throughout the day, and how I prepare for sleep. I own several health-monitoring devices, including a smartwatch that I wear nearly every day to track my workouts, stress levels, and sleep. Initially, I struggled to see the main differences between the Lumen and my smartwatch in terms of health monitoring. However, with the Lumen, you blow into the device, which provides more detailed information than just your heartbeat. It uses a CO₂ sensor and a flow meter to measure the CO₂ concentration in your breath, offering instant feedback on whether you're burning carbohydrates or fats for energy. This is something a smartwatch currently cannot do. Using the Lumen before workouts or after exercise can help you understand how your body burns fat. Additionally, it provides daily nutritional goals, which can be beneficial for those who struggle with dieting, as many d The presentation of the product is impressive. As soon as you open the box, you can see the quality and care that went into creating it. Priced at $199, it's reasonably priced, but considering its features, the cost may deter some potential buyers. After all, for a little more, you could purchase a nice smartwatch with various health features. On the other hand, the app is well-designed and far from basic. It offers numerous links and a wealth of information and articles to support your health journey, reflecting the careful thought put into the app, much like what you would expect from a membership service. However, this is where some people may lose interest. Yes, there is a subscription for the app and the data collected by the Lumen device. In 2025, many of us are overwhelmed by subscription services and hesitant to add more. I feel the same way. When you consider that a gym membership can cost around $20 a month, it's hard to understand why connecting to an app costs $20 a month (or $180 a year). As with everything, the costs add up. When you factor in the $20 monthly subscription along with the $200 for the device, it becomes quite an investment. However, if you get into it and use it daily, I can see its value. Fortunately, I may not need to stay on top of my health as much as others, so using it daily isn't something I find myself doing. Overall, I'm supportive of technology that helps people maintain their health, and Lumen is certainly doing that. While I may not invest in a membership, it's available for those who will find it helpful daily.

This is more of a hot take of Lumen than a comprehensive review since I’ve only incorporated Lumen into my daily routine for a week. I love the insights smart devices offer about my wellbeing and Lumen is not my first. So, in my experience, weeks of data points are needed before making a conclusion about a device’s worth. And Lumen actually needs a couple weeks use before it’s key metric, the “Flex score,” is revealed. Nonetheless after a week I do have a good feel about Lumen’s usefulness so I’ll discuss my experience with it so far in hopes it can help you decide if it’s a good match for you. Even in just a week I’ve learned a lot about my eating habits and how metabolism works thanks to Lumen. That said since I’m only at the start of this path I can’t yet give it 5 stars. But starting off at 4 is excellent, I think. THE LUMEN DEVICE AND LIFE The Lumen is unlike any other smart health device I own because it’s not passive. Before you purchase the Lumen you have to buy into its lifestyle for it to be useful. The Lumen’s task is to coach you to a healthy, “flexible” fat/carb burning metabolism, or if you’re already there to help maintain it. I was drawn to Lumen because while I think I live and eat healthy I still need help here. I remember the days I could enjoy my favorite treats like bagels and cake and work it off with ease. So, this is an excursion to see if I can get back there to some degree. Lumen determines your metabolic efficiency by analyzing your breath periodically during the day. With either science or sorcery, in almost real time, it calculates whether your metabolism is burning more fat or carbs or a mix of both. It takes that figure, matches it up to the time of day (wake up or bedtime) or activity (pre/post meal or workout) the breath is taken and guides you on what mix of carbs, protein, and fat should be in your diet for the day. When you do a pre-workout baseline breath it will let you know if you need some carbs before starting the workout based on your glycogen level and planned workout. It sounds like an easy process, but my first week was tough because Lumen’s recommendation to me severely reduced my carb intake – of course those are the “good” carbs not the ones that should be always limited. Because Lumen is personal its recommendation to you may be different. Regardless, Lumen is just a tool, like a hammer. Success requires action and commitment to be effective. I say this, having not gone “all in” initially and saw no improvement, why should I. But then I did go buy the book and I’m starting to get positive results. Expect to make lifestyle modifications. That is my overarching takeaway after a week. If you just give it breaths but don’t take its guidance all you are doing is driving hot air into a tube. I say this because it was hard for me to accept its low carb advice and I showed no improvement until I took it seriously. That’s on me. The Lumen itself is a cylinder with a premium feeling metal (but not metallic tasting) mouthpiece on the top and a vent at the bottom. The front has a sleek LED circle to note battery and power status plus, of course, a power button. That’s all there is to it physically. In coordination with the app, it works like a digital spirometer in that you inhale into the device to move a ball to a target in the app. You do this for four “long” seconds, hold your breath for ten more seconds, and the exhale back into the Lumen. At a minimum you must do this at wake up and bedtime, but it’s also helpful to get a reading at other key times like before and after meals or pre and post workout. Without doing this consistently Lumen won’t have enough data to coach you properly and it will also be harder for you to track your progress. The app needs mere seconds to show your current metabolic state represented as a carb:fat burning ratio. There’re five levels with one being mostly fat burning and five being mostly carb burning. The app explains what it means and how to proceed. I don’t perceive the categories to be de facto “healthy” or “unhealthy,” like, for example a BMI number. It’s just where your body is at that moment in time. Metabolism, I’ve learned, changes during the day and night. The goal of the Lumen is to lead you to a “flexible metabolism,” that efficiently burns both fat and carbs but not muscle. And to do that you have to live, what I call, the Lumen life. When it says go low carb, do it even though it’s tough. If you are unwilling the Lumen isn’t going to be a good use of your money. THE APP Like most smart health devices, the center of attention here is the app. Technically it’s free, but its muscle, and therefore the Lumen’s abilities, is only unlocked with a paid subscription service. So, it’s vital to include the cost into your buying decision. Also important, I think, is to read the privacy policy before buying since a lot of personal information is being shared or perhaps “donated.” Similarly, as with other smart health devices, the app attempts to “gamify” the process to make it more engaging. It doesn’t make eating fewer carbs easier, but maybe more mentally rewarding. Generally, it does a good job at this and providing metabolic education. I think it could do a better explaining my specific scores and how that fits into the scale of where I should be. But I have learned a lot about the metabolic process from Lumen. Because metabolism is just one piece of one’s health & fitness puzzle the Lumen app can integrate data from other fitness apps and devices to give you an even clearer analysis. The list of compatible apps is long, so I won’t list them all. If it’s popular it’s probably compatible. I connected my Apple Watch (Apple Fitness and Motion and Health) which shares my sleep and workout information with Lumen. The app has four areas but one is a link to Lumen’s Facebook community and another is generic education on metabolism. The two others are user specific. “Today,” as it sounds is where that day and week’s data is displayed and recorded. You’ll find your breath analysis, daily timeline, and nutrition plan here. If you like you can enter in your meal contents. I’ve always been lazy about meal logging and no change here. But the app tries to ease the inconvenience with the ability to scan UPC codes, detect by photo, or voice log. It’s still a time sink for me, but maybe I’ll get on board. Also, in the app, if you are super dedicated but also busy too, you can order premade meals based on Lumen’s fat and carb recs in app with a week’s notice. Personally, this kind of blatant upsell, especially in a paid-for subscription app, is not my thing and I find distasteful. The other personal section is titled “Me,” and is where you’ll find all your data points over time boiled down to charts and graphs so you can see your progress or not. This is also where the Flex score is posted. LUMEN BOILED DOWN The Lumen is a simple (but smart) device that can help guide you to a health metabolism. But it requires a commitment from the user as well, both in adhering to its sometimes tough eating recommendations and by paying for a pricey subscription. The app is intuitive and presents information and education in an easy-to-understand way. I’ve only been using it for a week but once I started heeding its eating advice I did see metabolic improvement so I’m optimistic that it going to be a fantastic tool to keep me in a more healthy lifestyle, but also to be able to cheat in the future with the ability to burn off a slice of cake now and then a little easier than I now can.

I have been using the Lumen breath analyzer for a little over three weeks, and it has already provided some highly useful insights into my metabolism and metabolic health. Inside the box are the Lumen device, a charging stand, a detachable USB-C to A cable for the stand, and a carrying pouch. The cable cannot connect directly to the device to charge, so the Lumen can only be charged with the stand. If traveling, make sure to pack the stand too, and not just the cable. The initial charge took several hours, but after over three weeks of use, the device is displaying 60% battery capacity remaining. The light ring pulses during charging and goes solid once the device is charged. The Lumen works by measuring my breath to determine my metabolic state. The device is simple to use, and the Lumen uses helpful visual and audio prompts to ensure breath is accurately measured during both inhale and exhale. I power on the Lumen, allow the device to warm up. Warm up can take up to thirty seconds but typically takes 10-15 seconds on average. I then follow the app prompts, inhaling through the device to keep he ball within the target circle for four seconds, hold my breath for ten seconds, and exhale back into the device keeping the ball within the target circle for six seconds. If I mess up (for example, exhaling first instead of inhaling) the Lumen will advise and restart the test after a quick pause to allow the device to reset. The Lumen then processes the breath sample and displays my current metabolic state, revealing whether I’m mostly burning carbs, fat, or both. My first result indicated I was burning carbs and fat fairly evenly and advised that the next day would be a low-carb day. It then offered meal plan suggestions and recipes accordingly. Subsequent measurements revealed different patterns based on time of day, meals consumed, activity, etc. After two weeks of measurements, I was shown my flex score which measures how flexible my metabolism is at burning fat and carbs. While waiting on my flex score to unlock, I educated myself on nutrition and metabolic health using the abundant amount of informative content within the app. I am learning all about metabolism, the role of mitochondria, and how things like stress, cortisol levels, diabetes, and other health factors can affect metabolism. I’m even learning why some people constantly crave sweets. The Lumen helps me regulate my metabolism by offering tailored meal plans and macronutrient tips to help correct imbalances. One really useful feature in this pursuit is that the app can utilize AI to identify and record meals using my smartphone’s camera. The app also logs my movement and fitness via my smartphone’s health app. I initially frequently fell on the mostly burning carbs side (4, 5) of the scale due to my moderately high-carb and poorly regulated diet. Since I began following the Lumen app guidance, my results now skew more frequently towards fat burning, and others typically fall in the even range (3), where my body burns both carbs and fats at a near-even pace. Use of the Lumen requires a moderate amount of discipline. I must remember to use it daily when I wake, throughout the day, and at bedtime. Waking and bedtime are the two most important measurements. All others are optional, although they can offer additional helpful insights. The breathing and audible prompts can be loud enough to disturb others nearby, especially if measuring really early in the morning or late at night. I disabled the audio prompts and either go into the bathroom first or find other ways not to disturb my sleeping spouse when measuring. To make it all worthwhile, I try to strictly follow the macronutrient guidelines to effectively coax my body into processing my food more efficiently and burning fat. I perused the meals and found some I liked, some I didn’t. I will likely make some substitutions using the suggested macronutrient amounts from Lumen as a guide. I also must be disciplined in the timing of my meals and stop the poor eating habits that have led to weight gain and suboptimal health. The wealth of helpful knowledge and tips that the Lumen app and plan offer can be used with the metabolic measurements and flex score on a continuous basis. The tips are presented as short silent videos, so they require reading to follow. I don’t know if there is an option for visually impaired users, but I couldn’t find any sound options. The tips required I view previous tips before additional tips would unlock. I wasn’t initially fond of the read-to-unlock-and-continue format, especially since most of the videos I was most interested in are buried beneath several less interesting videos, but I get it. Too many people are stubborn and will want to skip the learning portion and take shortcuts. This device is not for anyone seeking shortcuts because, again, it requires moderate discipline. Lumen also provides an in-app link to their Facebook social media page and an in-app members forum. I rely on the forum, which I prefer over using social media. Another requirement for full app functionality is a paid Lumen membership. Membership options include monthly or annual. The biggest benefits I see with membership are the macronutrient suggestions and tracking, meal suggestions and recipes, and seeing how my body responds to certain meals, exercise, and stress. Much of this can be accomplished manually by people good with meal planning and nutrition knowledge. That’s not really me, so I’m giving the annual membership a go, and if I continue seeing benefits, will renew. The Lumen has been truly helpful for me, particularly in my situation. I’m in recovery from major surgery and spent nearly a year with severely limited mobility. It did a major number on my metabolism, muscle mass, and cardio fitness, all of which plummeted. I was trying to go at it on my own, but it wasn’t going well. I was continuing to lose muscle while accumulating more fat. The Lumen has helped me make better eating decisions and helped tailor my recovery training for maximum benefits. For example, I started running on high-carb days and noticed measurements taken after exercise were in the fat-burning zone rather than even or carbs. That was a major factor in me deciding to give an annual membership a go. And so far, Lumen hasn’t disappointed yet.