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Lumen Metabolism Tracker Review: How to Hack Your Diet

Disclosure: This is a sponsored post containing affiliate links. We received compensation and courtesy product from Lumen in exchange for our honest review only. All opinions expressed here are our own. Learn more.

William Barton Writer & Photographer   Updated: 
lumen metabolism tracker review for health

With so many weight-loss schemes and wild promises thrown around, it makes sense to have a bit of skepticism toward any new technology that supposedly “hacks” our health.

In our Lumen metabolism tracker review, we’re taking a close look at this sleek device to see if it’s really worth the investment.

Talk about a bio-hack...
The Adult Man Image/Icon Image source: Lumen

Bottom line: The Lumen metabolism tracker is a nifty device that helped me understand how my daily rhythms impact my overall health, and led me to make a few tweaks to my routine that I think will have massive benefits over the years. I think of Lumen as an investment like a course or training program---if you follow it for eight weeks, you’ll get tremendous value, even if you never use it again.

Ratings: The Adult Man Image/Icon  Design The Adult Man Image/Icon  Quality of Materials The Adult Man Image/Icon  Value for Money The Adult Man Image/Icon  Craftsmanship The Adult Man Image/Icon  Customer Service
  • Gives an accurate broad picture of how your diet affects your metabolism, which can really cause you to look at the cost of certain habits
  • The app has tons of useful dietary and exercise information
  • The app acts as a fitness center, where you can track your weight, carb intake, and more
  • Lumen’s customer service is super helpful and extremely responsive
  • The daily dietary recommendations are difficult to follow: I meal prep because I never want to plan my food for the day when it’s the day-of---so, yes, I know exactly what I’m eating tomorrow

Maybe you’ll resonate with me on this:

The first part of 2020 took a toll on my health. I was working my tail off, not sleeping so much, and essentially abusing my body with my diet. I picked up 10 extra pounds and felt terrible.

Then, sometime around June, I busted out of the cycle and lost those ten pounds, plus a few extra. 

Then, sometime around November—not at all related to US election stress—I picked up those pounds I lost and said ‘hello’ to a few more. 

Phew. What a time. 

Since 2020 ended and life has become a shining green pasture, I’ve shed the weight again, and I’ve become really interested in tools and gadgets to help me along the path. 

And that led me to Lumen—a metabolism tracker that supposedly can discern whether you’re burning carbs or fats, and gives you dietary recommendations based on that information.

After using it for a month, I’m ready to share my experience so you can decide whether Lumen is right for you. 

What Is Lumen?

Lumen metabolism tracker device top down

Lumen is a slimmed down accessible version of the bulky Respiratory Exchange Ratio (RER) test typically done by doctors or sports medicine practitioners for professional athletes. 

By measuring the CO2 in your breath through a portable breathalyzer device, Lumen feeds the information into a tracking app that gives you an easy-to-read 1-5 score for your metabolism. 

If you’re a 1 or 2, you’re burning mainly fat (between 65%-90%). If you’re a 3, you’re balanced between burning carbs and fats. And if you’re a 4 or 5, you’re mainly burning carbs. 

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The idea is that your body will increase its metabolic flexibility, so you’re always burning the right kind of calories: carbs when you’re most active, and fats when you’re resting. 

After two weeks of consistent testing, Lumen gives you a score to rate your metabolic flexibility (called a Lumen Flex score). If you follow the nutritional guidance provided by the app, you should ideally be increasing your Lumen Flex score, helping you with your body transformation goal. 

Lumen Metabolism Tracker

Lumen is an excellent tool for anyone looking to gain more insight into how their diet affects their health and performance. If you want a better understanding of how certain foods and eating schedules change your metabolic rate, then the Lumen is a helpful gadget for you.

Shop Lumen

Things to Consider Before Buying a Metabolism Tracker from Lumen

Lumen metabolism app tracker

Getting a consistent reading from Lumen takes consistency on your part. Expect to measure your breath several times a day for at least the first two weeks so your Lumen can get to understand your rhythms. 

It does take a bit of effort, so I’d only recommend it for people who are ready to make their health their priority. 

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To truly use Lumen to its maximum potential, you’ll want to be flexible in your daily diet so you can follow its advice. Plus, if you’re not committed to your body transformation goal, remembering to breathe into the device three or four times a day is going to be a struggle.

That said, the tracking process is really easy, and I picked up some key insights into my diet that I believe will have a huge impact on my well-being in the long run. So how hard is it really to breathe into a device a few times a day with lifelong nutritional knowledge as the payoff? 

Lumen Metabolism Tracker Review

Lumen works in two parts: the device itself, and the app it connects to. 

The device just measures the CO2 in your breath, but the app is where all that data comes together. 

The Lumen

Lumen metabolism tracker packaging and device

The Lumen device is a sleek black breathalyzer-style piece that almost looks like a UFO train-whistle. 

To me, it’s one of the most pleasantly designed things I own: the matte black rubberized body feels like velvet, but where you place your lips is made with glossy stainless steel. The cap is magnetically attached, which feels like the future, and a small purple LED ring lights up when you turn it on. 

Having the metallic mouthpiece is critical, because it’s easy to swab with an alcohol pad every so often just to keep things clean. I wouldn’t wash it with water, though, as the device isn’t waterproof.

Lumen metabolism tracker packaging

I like that the Lumen is easy to carry around and can fit in your front pocket. It comes with a zippered pouch so you can toss it in your bag without getting those “bottom-of-the-bag” crumbs in the device. Am I the only one who’s got those? 

I work in a co-working space, and it’s a bit awkward to bust out what looks like a vape-pen or breathalyzer in the middle of the office, so I head off to the bathroom stall to get my readings in the middle of the day. 

The device comes with a USB charging dock. Most people have an iPhone or some sort of USB charging block already, but it’s important to note that the Lumen doesn’t come with a USB charger block. So if you don’t own one, you’ll need to charge through your computer. But most people have one at this point, so it shouldn’t be a huge issue. 

The App

Lumen metabolism tracker and app in use

The most important reading of the day is in the morning. And it’s important that you get your first reading about twenty minutes after you wake up. 

I weigh myself every morning and log the data, so for me it was a natural add-on to also breathe into my Lumen and get a metabolism reading. But apparently your body burns up carbs right when you wake up, so my readings always seemed high (4s). 

There were a few days I cut way back on carbs to see if I could change that level, but I only ever got a reading I felt reflected my diet when I did the reading about 20 minutes after waking. 

Lumen metabolism tracker in use

As you get your Lumen calibrated for the first few weeks (it takes two weeks to give you your “Lumen Flex Score”), you can log measurements before working out, after eating, after fasting, or really any time of day. 

This is the most interesting part to me: to understand what fuel my body is burning through different parts of my day. 

I have a pretty strict regimen I live by. I start my day with a 90 minute morning routine, followed by about three hours of writing, then a walk to the office, about five hours of emails and admin stuff, then a walk to the gym, finished with an hour of weight-lifting. 

I’ve naturally fallen into a rhythm of not eating for that whole morning chunk of about five hours. And when it’s time for me to go off to the office, I’ve learned that I’ve been burning mostly fat the whole time. 

model using Lumen metabolism trackerjpg

This prolonged period of not-eating is called intermittent fasting, and it’s all the rage in the health world right now

There are tons of purported health benefits, though I’ve been doing it for the past year or so purely because I find it easier to focus on my writing when I’m hungry (or maybe it’s because my gut isn’t soaking up resources from my brain). 

Now, Hemingway was a big fan of creativity when hungry. Which leads me to one of “Uncle Willie’s” crazy theories: is my mind more sharp when I’m burning fat as fuel rather than carbs? Did Hemingway create his famous minimalist writing style because he was a fat-burning, big-fish hunting machine? Who’s to know?

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Anyway, based on your morning metabolism reading, Lumen suggests a diet plan to you based on macro-targets. 

If you’re not familiar with macros, it works like this: there are three types of fuel—carbs, fats, and proteins. You need them all. And the proportion you eat them is very important. In a typical day, I eat 200g of carbs, 200g of protein, and about 80g of fat. Carbs and protein have four calories per gram, and fat has nine calories per gram. So when you combine those numbers, you get your target caloric intake. 

So my target caloric intake is around 2,400 calories. As a 6’1” 30 year old male, that puts me at a “caloric deficit,” which means I should be losing about a pound a week, so long as I’m about 400 calories short of what I need to maintain my weight. 

When you plug your height, age, weight, level of activity, and desired outcome into Lumen, it’ll automatically give you the macros you need to hit in order to reach your goal.

So if you want to lose weight, it’ll give you the “macros” so you can be in a slight caloric-deficit—not so much that you’re starving all the time, but just enough so that you can slim down over the course of a few months.

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If you want to bulk up, it’ll put you in a slight “caloric surplus” so you can add muscle and weight to your frame in a steady, healthy way. 

My only issue is that you don’t get this plan until after you’ve done your first reading in the morning. If you had a slice of bread at 8pm, there’s a chance you may be burning carbs in the morning rather than the desired fat-burning. Lumen will then suggest you go light on the carbs that day. 

I love food, but I never want to be planning what to eat the day of because I have so many other things I need to accomplish. On Monday morning, I already know what I’m eating Thursday at lunch. So having my macros change on me in the morning isn’t something I’m willing to follow. 

Another way of putting it is that I’m willing to do a low-carb day (20-30g), but I need to have it planned out so I can buy the right food at the grocery store and have my meals prepped ahead of time. 

Willpower is a fickle thing, and if I’m hungry when chips are around, I’ll completely smash them. But if I have healthy prepped meals, they become the easiest thing to eat, so I just get lazy and pick the healthy option. 

Lumen Metabolism Tracker

Lumen is an excellent tool for anyone looking to gain more insight into how their diet affects their health and performance. If you want a better understanding of how certain foods and eating schedules change your metabolic rate, then the Lumen is a helpful gadget for you.

Shop Lumen

What I’ve Learned

Using Lumen, I’ve learned a few things that I’m going to hold on to for the foreseeable future. One, intermittent fasting is awesome. Getting a 16-hour overnight break from eating allows your body to settle into fat-burning mode, and I’ve felt a lot more energy when I practice this. 

Lumen allows you to track when you’re in the fat-burning zone, so you can change your diet the day before to make sure you spend enough time there.

I’ve also learned the importance of getting enough carbs right before a workout. This literally translates to me eating an apple before my weight-lifting sessions so my body kicks into carb-burning mode. 

It may not sound like a massive difference, but consider this: if I have 10% more energy and I put it into four workouts every week, how much will that little nugget of nutritional info compound? One little change, when consistently practiced, can be completely transformational. 

My Lumen Flex Score needs some work: I’m between a six and seven (though I think I was measuring my metabolism too soon after waking up, so it’s a bit skewed still). In any case, I’ve added low-carb days into my weekly schedule on the days I’m not working out to help increase my body’s metabolic flexibility. 

What do Other Reviewers Say About Lumen? 

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Lumen has an “excellent” rating on Trustpilot at the time of writing.

Most people using the Lumen are using it for their weight-loss goals, which is a bit different than what I’m aiming for (muscle gain). For the folks who were dedicated and followed the app’s instructions, there were some impressive results. One person claimed to have lost 25 pounds in seven weeks. 

Lumen gets high marks for their customer service, which I’ve experienced, too. They’re super responsive if you have any issues, and the team reaches out via automated email several times to make sure you can hit your health targets.

My Thoughts Overall On Lumen

What I Like

  • Lumen gives a broad but accurate picture of how your diet affects your metabolism. This helped me make big changes (no midnight pizza), and small tweaks (an apple before my workouts), and have led me closer to my fitness goals.

  • The app has a ton of useful exercise and dietary information, and if you make it your priority to follow its advice, you’ll be well on your way to the body-composition you’re after. 

  • Because you can track your carbs, weight, and exercise information in-app, it acts as a sort of digital fitness center where you can get the big picture of your health journey. 

  • Lumen’s customer service is super responsive.

What I Don’t Like

  • Because I’m a meal-prepper, I had a difficult time following the “day-of” advice Lumen provided. I would love to see a recommended weekly diet, as that’s more manageable for my lifestyle. 

Who is Lumen for?

Lumen is an excellent tool for anyone looking to gain more insight into how their diet affects their health and performance. If you want a better understanding of how certain foods and eating schedules change your metabolic rate, then the Lumen is a helpful gadget for you.

The Verdict

I see the Lumen almost as a course to learn more about the link between diet and metabolic rate. 

The first two weeks gave me a ton of new insights into how my eating habits, including the time of day and which particular foods, affected my performance—both at work and in the gym. 

Week three and four were all about fine-tuning, and that’s when I picked up a few tidbits that I’ll carry with me long-term. 

I went into my experience with Lumen knowing a decent amount about nutrition, but I was able to use what I learned with the device to make a few changes that have really helped. And I know those small changes are going to lead to a massive impact a few months down the road. 

I wasn’t able to follow the day-to-day nutrition advice Lumen offers, because my primary focus is on my business, and I meal prep my food to support that. 

Still, I learned a lot from Lumen and I definitely have more energy after implementing some of my insights from the app. 

If you’re at a plateau, or want to shed a few pounds, the Lumen can shine a light on how your diet fits into your overall fitness goals. To me, that’s totally worthwhile.

Lumen Metabolism Tracker

Lumen is an excellent tool for anyone looking to gain more insight into how their diet affects their health and performance. If you want a better understanding of how certain foods and eating schedules change your metabolic rate, then the Lumen is a helpful gadget for you.

Shop Lumen


Does Lumen help you lose weight?

Lumen offers personalized nutritional information based on your fitness goals, body type, activity level, and metabolism. If your goal is to lose weight and you follow Lumen’s advice, you’ll lose weight.

Can you track your metabolism?

Yes, you can track your metabolism. Trackers like Lumen can determine whether you’re burning carbs or fat based on the level of CO2 in your breath.

Is the Lumen metabolism tracker any good?

Yes, the Lumen metabolism tracker is able to determine whether you’re burning fats or carbs. The readings aren’t as absolutely precise as what you’d get by going to a specialized sports medicine doctor and getting a reading with the bulky equipment they offer, but you can use the Lumen any time and it fits in your pocket.