As two engineers who have spent the better part of a decade researching health, wellness, and the tech that goes with it. Today we wanted to share our honest Lumen review.

Over the years, we’ve become more skeptical of diets, supplements, and products touted to transform our health. The majority are a complete waste of time and money.

Lumen seemed different because it tracks an important health metric, your metabolism, in real time. Upon writing this Lumen review, we’ve been tracking our metabolism for three months.

Our experience has been… interesting. Does it really work? Yes, but does that mean it’s worth it? Not for everyone.

75 Hard Printable Checklist

Lumen Metabolism Tracker Review

We love data and science, so this was right up our alley, and we had high hopes. But as skeptics, we had several questions, mainly:

How accurate is it? How much detail does it provide? Does it really help optimize intermittent fasting windows? Could we lose weight with it or optimize athletic performance?

The goal of our Lumen review is to answer those questions as well as share our surprising experience as a couple using Lumen together.

It turns out that our metabolisms are completely different, despite eating our meals together, going to bed and waking up together, and often doing the same workouts.

This Morning With My Lumen

After three months, I am still fascinated that a little device can tell you not only, in real-time, what your metabolism is doing, but what to eat today based on what it is.

This morning, before publishing our Lumen review, I sat down with my Lumen and cup of coffee and exhaled into the little pocket-sized device. My body was burning 95% fat and 5% carbs. My intermittent fast was working. Great.

Although I had been ready to grab my granola, I decided to wait a little longer to capitalize on my fat burn.

Scrolling through the app, I saw that my measurement updated the day’s meal plan. It was a low-carb day, with macro targets of 66 g of protein, 97 g of fat, and 105 g of carbs. Of my carbs, it recommended that I eat 80 g (or 76%) of my carbs by lunch.

An hour later and after a workout, I went back to my Lumen. It had updated once again as it connected with my Apple Watch and saw that I had exercised. It recommended that I add a bit more protein. Cool, can do.

Once more, I exhaled, and 10 seconds later saw that my metabolism had shifted to burning 50% fat and 50% carbs. I had learned from Lumen that once my body switches back to carb burn mode, I’ve fasted too long. Noted, it seemed like a 13-hour fast was just right for me today.

With that, I grabbed my granola, happy that I didn’t waste more time fasting because I was h-u-n-g-r-y!

Thanks, Lumen, and I’ll check in with your before bed.

What is Lumen?

The Lumen is an at-home device that measures your metabolism in real-time. It works like a breathalyzer and measures the carbon dioxide in your breath to share if you’re burning carbohydrates or burning fat.

While a simple concept, this is the first time we’ve seen a metabolism tracker at home.

Lumen Review how does it work and what does it measure

What is special about Lumen?

For years, the only way to know what your metabolism was doing was to go to a lab or clinic. Not only was this inconvenient, it was incredibly expensive and mainly available only to professional athletes.

Lumen is special because it’s a new invention. The device itself is small, sleek, and easily fits into your pocket. Given that it takes just 30 seconds for a measurement, it means that you can measure your metabolism any time and anywhere you want.

How does it work?

What exactly is Lumen measuring? While breathing into the device, the Lumen is measuring the concentration of CO2. Based on that measurement, the app tells you in exact percentages what your body is doing.

You’re given a grade of 1-5 on the fat-burn scale, a metabolic flexibility score, and shown what you’re burning right then, like 80% fat and 20% carbs.

Yes, it’s that detailed!

Lumen metabolism tracker review measuring carb burn versus fat burn

Is Lumen Legit?

We did our research before we considered “hacking our metabolism.”

First, we learned that Lumen does NOT offer advice to follow a strict keto diet. This would have been a deal breaker for us. Next, it was clear that the company had invested in research and development. 

According to one 2021 validation study conducted at San Francisco State University, the Lumen is proven to work, providing accurate CO2 levels in your breath. Since then, Lumen has expanded their research by partnering with several top institutions.

Lumen review is lumen scientifically proven

Additionally, Lumen’s best feature, in our opinion, is that it’s a smart device. It begins to learn your body’s habits and will give daily food recommendations on how to improve your metabolism. 

In addition to nutrition recommendations, the Lumen metabolism tracker and app factor in other key lifestyle factors—movement, sleep, stress—that are critical to optimal health.

Lumen metabolism tracker review is it legit and what lifestyle factors it improves.

Lumen Review: What We Learned From Using the Metabolism Tracker

Ryan and I have completely different health goals.

Ryan wants to build muscle, optimize his intermittent fasting results, and be a strong distance runner. I was looking to manage my hunger while breastfeeding and learn how different meals affect my body.

Between the two of us, while testing for this review, we used Lumen to discover:

  • How specific meals affect our metabolism
  • How our workouts affect our metabolism
  • If we’ve fasted long enough — or too long
  • How sleep affects our metabolism
  • What our bodies tell us when we have a craving
  • How to get over the hump of a weight loss plateau/intermittent fasting plateau

While it wasn’t our goal, we both improved our body compositions with Lumen. Ryan gained about 5 lbs. of muscle and I lost 2 lbs. of fat — all without changing our routines that much. That’s how much awareness and small nudges from Lumen were able to change our habits! Pretty amazing.

What’s Metabolic Flexibility and How Does It Help Me?

Let’s quickly jump into the science of why your metabolic flexibility matters.

Metabolic flexibility is a measure of how well your body can choose between fuel sources. Our main fuel sources come from the carbs and fat we eat. Plus, about 5% comes from protein as well.

Depending on a variety of factors, such as your diet, exercise level, insulin sensitivity, stress levels, sleep quality, and so forth, your body will decide which source of fuel to use.

Of course, people are keen to burn fat but it’s important to also burn carbs. In fact, much of your carb consumption is used by your brain!

Why try to “hack your metabolism?”

Having a healthy metabolism has an array of benefits, including weight loss, improved body composition, higher energy levels, better sleep, and a stronger immune system.

Since the right balance is necessary, a device like Lumen is beneficial for improving your metabolic health.

Lumen review why track your metabolism

Our Lumen Review and Experience. Does It Really Work?

After three months of putting it to the test, here is our experience and review of the Lumen metabolism tracker.

A Couple’s Experience with Lumen

Both Ryan (male, mid-30s) and I (female, mid-30s) have been using the Lumen for several months. Mainly, we used it as a tool to collect data.

Ryan used the Lumen to optimize his intermittent fasting window while I focused on bettering my metabolic flexibility as I weaned from breastfeeding.

Our biggest takeaway from this Lumen review is that our bodies are completely different. I know (duh!) but we eat the same meals, do the same workouts, and go to sleep and wake up at the same times.

We thought there would be more similarities than differences, but we were wrong.

1. Metabolism Change with Carb-Heavy Meals

First, my body was far more responsive to meals than Ryan’s. If I had a carb-heavy meal it would affect my metabolism quickly. I would swing from burning 70% fat to 70% carbs within hours.

For Ryan, it seemed like he had a longer delay — closer to 12 hours. What we learned from this is that I should eat my carbs earlier in the day, whereas Ryan had more flexibility if he ate them at night.

We were happy to see complex carbs such as black beans didn’t cause the same swing as pizza or pasta. 

2. Metabolism with a Higher Fat and Protein Diet

Second, when we started, I was always wondering, “Why am I always burning carbs on Lumen?”

It turns out, both Ryan and I weren’t eating enough healthy fats and protein. As clean-eating vegetarians, this wasn’t a surprise, yet as we added in both fat and protein, we saw our fat-burning levels increase.

As you can see, it took about 4 weeks of consistent use to finally achieve morning fat burn and blow a 2. After that, I was consistently at levels 1 and 2 in the morning.  

Review of lumen metabolism tracker and alex's results

Ryan’s metabolism responded to the higher protein and fat after about 2 weeks, however, his morning levels were less consistent than mine. 

In the Lumen app, you get tons of graphs like these, which are extremely helpful to monitor progress. 

All of us are doing our best when it comes to eating well, yet without having actual data, you may still be missing the mark. We were, and the Lumen was especially helpful because that ‘mark’ is a moving target!

While we may be in the minority of not eating enough fat and protein, given how many folks eat low-carb and low-calorie, they may be missing out on a better balance while helping improve their metabolic flexibility.

Does Lumen really work? For me, yes. Check out this increase in metabolic flexibility!

Lumen review and metabolic flexibility results over 3 months

3. Metabolism and Intermittent Fasting

Third, my body’s fasting window was much shorter than I thought.

While I wasn’t following an intermittent fasting schedule because I was still breastfeeding, I naturally fasted 13 hours overnight while I slept. Well, this turned out to be too long.

I used the Lumen to optimize my fasting window by measuring if I woke up in fat-burning mode, as I often did. Once my body flipped to carb-burning (my body’s response to stress), it was time for me to eat.

Usually, I could feel the difference because, suddenly, I would become ravenous and confirmed with hourly Lumen checks until I was in carb-burning mode.

All in all, I made my fasting window shorter by about an hour.

Meanwhile, Ryan could fast for several more hours, to match the common 16/8 fasting schedule. However, on days following a long run, he had to break his fast earlier, after 14 hours on average.

4. Metabolism and Exercise

Fourth, Ryan had his best morning workouts when he was in fat-burning mode. He felt more energized and strong.

If, before his workout, Ryan’s Lumen told him that he was burning carbs, he felt better when eating a small snack, like a banana and peanut butter, for added energy before his workout.

We’re happy we did the testing for this Lumen review because the data was very useful to maximize every training session. 

5. Metabolism and Sleep

In 2017, Ryan experienced major physical health symptoms from burnout caused by sleep deprivation. Ever since we obsess about our sleep quality. 

When our night’s sleep was disrupted or cut short, our metabolic flexibility score decreased. If the Lumen metabolism tracker can nudge people to focus on their sleep, that’s a huge win. 

Is Lumen Worth It?

We found the Lumen to be an incredibly helpful tool for our health. The results were impressive and they didn’t require much work at all.

But for $299 without our 10% off Lumen discount code RYANANDALEX — and sales are run frequently — is Lumen worth the money?

Yes… and no.

Lumen Review: Who should try it?

For people who have battled their weight and metabolism for years, the Lumen will be indispensable for you.

Now you can see in real-time what your body is doing with what you’re giving it (food, sleep, water, movement, stress, and otherwise).

What we love about the Lumen is that the recommendations are personalized to your body — because as you know, no health plan is one-size-fits-all.

Lumen does not promote a restriction diet, something we are completely against. Lumen will instead guide you on what to eat, and you can choose to listen, make small or big changes, or simply continue learning about your body.

Metabolic flexibility is one of the single best metrics that you can focus on. Why? Because weight loss is simply a natural side effect, alongside a bevy of other overall health benefits.

So, who is the Lumen not for?

Who should think twice about Lumen?

For someone who is in great health and maintains weight and energy levels without trying, it sounds like your metabolism is pretty well optimized.

You’ll still love the data that Lumen can share because we’re all always striving for betterment. Is Lumen metabolism tracker a good tool for athletes? Absolutely, as long as it’s within your budget. 

The Pros

While researching, testing, and writing up this Lumen review, these are the things we loved about the Metabolism Tracker.

  • Unparalleled insight into how your activities and diet affect your metabolism
  • Clear and precise measurements: “You’re burning 35% fat and 65% carbs right now”
  • A metabolic flexibility score that spurs you to improve every week
  • Daily eating plan based on your measurements: “It’s a low-carb day. Eat 105 g of carbs, 66 g of protein, and 84 g of fat.”
  • Helpful videos into bettering your metabolic health and general wellness
  • Easy-to-follow visualizations, graphs, and trend lines to monitor your health
  • Connects seamlessly to your Apple Watch, Google Fit, and Garmin to log workouts, which affects your recommended daily diet
  • The measurements are quick and take less than 30 seconds
  • Works well just by using it once in the morning, but has improved accuracy if you use it throughout the day
  • Even without a subscription, you can still see what your metabolism is doing — you just won’t have the insights and nutrition plan.

While the pros and cons list in our review of Lumen is heavily positive and compelling, there are still some things we disliked about the Lumen.

The Cons

On to the not-so-great things section of our Lumen review. Actually, this list used to be much longer, but they recently made updates to their pricing and subscription plans, so now we only have one qualm:

  • Two people cannot use 1 Lumen because it adapts and learns to your individual measurements

The cost of the device is normally $299, but we have a Lumen discount code of 10% off with RYANANDALEX. This includes a one-month subscription, and after that, it is $19/month — but the device and measurements are yours forever.

While we think you’ll need at least 3 months of the subscription to initially dial in your metabolism, after that, you can probably cancel and just subscribe periodically or when you find you need it (aka you’re burning all carbs and no fat).

How much does Lumen cost?

The Lumen device normally costs $299 but you can apply our 10% off code of RYANANDALEX — and sales are run frequently. This includes a 1-month free subscription to the Lumen app. After the first month, the subscription is $19/month.

What you get with the subscription is your specific meal plan recommendations based on your day’s metabolism, daily macro targets, and lifestyle recommendations to optimize your metabolic flexibility.

Without a subscription, you can continue to take real-time metabolism measurements however often as you’d like.

In our initial research for this Lumen review, we thought the subscription was expensive, at $19/month after purchasing the device. That’s $4 more than what we pay for the industry leading online workout and nutrition platform

After testing and documenting our results, we think it’s a steal. After all, nutrition is 80% of the battle, right?

It’s incredible not only to get real-time metabolism measurements but also to get real-time nutritional targets based on what your body is doing right now!

We work with thousands of clients each year who are working to better their health. In our experience, the average person is spending $50-$150 a month on something (pills, supplements, weight watchers, keto meal delivery, etc.) that’s not helping them reach their goals. 

Spending $250 for the device and $19 a month for Lumen is a no-brainer.

What comes in the box?

Unboxing and getting started with your Lumen is fun and seamless. They even include a thoughtful thank you note. 

The device is great and we love the magnetic cap (our 1-year-old loves playing with it too). The best this is the carrying case. It protects the device when dropped (accidentally tested that) and it’s nice to travel with. 

An unboxing Lumen review from two materials engineers: they didn’t cut any corners. Everything is top quality. 

Lumen metabolism tracker review what comes in the box

Lumen Metabolism Tracker Review FAQs

Before we started our Lumen review had tons of questions, and I am sure you do too. Fortunately, once you get your Lumen and connect it to the app, the program is incredibly easy to understand. 

The Lumen Facebook Group is a great resource, otherwise, feel free to ask us in the comments section of this article.

Do people lose weight with Lumen?

Yes, there are tons of testimonials on their website and both Ryan and I achieved our weight goals.

The Lumen app collects your real-time metabolic data. Then it helps you lose weight by giving you a customized daily meal plan and telling you exactly what to eat. 

It includes other helpful tools for your weight loss journey, such as the ability to track what you eat and set daily health goals recommended by Lumen.

Lastly, and unexpectedly, we loved the “Daily Dose” videos. They have a large selection of videos to guide you along your health journey and we were impressed with the short, concise, and motivating content.

Lumen app review tracking, setting goals, and learning

What’s the deal with Lumen and intermittent fasting?

For intermittent fasters, especially those who don’t have a lot of body fat to lose, the Lumen metabolism tracker is an absolute game-changer.

Once you’re in fat-burning mode, which is most common in the morning, and your body switches to carb-burn mode, it likely means that you’ve fasted too long. What’s likely happening is Lumen is picking up on your higher cortisol levels or ketones.

This information is invaluable because this increase in stress hormones means you could be using protein for fuel, which is not what you want.

How quickly does Lumen work?

It’s not immediate. It takes 2-4 weeks for the device to learn your body and output a metabolic flexibility score. Then, your should be able to see improvements in your score within a week or two.

Plan on using the Lumen metabolism tracker for 1.5 months before seeing and feeling solid flex score improvements.

What is a good flex score? The Lumen app will tell you and guide you on how to improve. Here are the ranges:

  • Low flexibility – 0 and 6
  • Medium flexibility – 7 and 14 (this is good!)
  • High flexibility – 15 and 21 (this is even better!!)

What if my Lumen levels are not good? Well, I hate to say it, but you have low metabolic flexibility. I’ve been there. You need to focus on eating the right type and amount of carbs (listen to the Lumen app’s suggestions), moving more, managing your stress levels, and focusing on getting quality sleep.

When should you use your Lumen?

The most important is the morning measurement. Take it when you wake up before eating anything.

We took measurements before and after (wait 30 minutes) workouts, as well as before and after (wait 60-90 minutes) meals as well. 

In our experience, the most helpful measurements to take are:

1. First thing in the morning measurement
2. Late morning custom measurement to know when to break your fast
3. Pre-workout measurement 

Lumen review when should you use your lumen

Closing THoughts on the Lumen Metabolism Tracker

The Lumen offers, in the first of its kind, invaluable information on your metabolism. You can see exactly what your body is doing at that moment.

How did your body respond to that workout? That less-than-great sleep last night? Or what are the repercussions of your weekly pizza and beer night?

If you’ve tried dozens of diets and nothing seems to stick, don’t think twice about trying the Lumen. 

Many factors contribute to overall health and weight loss, from what you eat, genetics, medication, how you exercise, age, and hormonal shifts. It’s hard to find a healthy lifestyle and eating plan that covers all of these bases — and one that worked 10 years ago may not work today.

Leave it to Lumen to create the plan for you, using your own body’s metabolism measurements. No more guessing, just follow the data for better health and weight management.

We’ve immensely enjoyed using our Lumen. It’s easy, fast, and endlessly fascinating. Three months in, we optimized our intermittent fasting windows and changed our diets to match what our bodies need (in both of our cases, more fat and protein). Best of all, our energy levels are higher than they’ve been in years.

If we didn’t answer your questions in this lengthy Lumen review, please let us know in the comments. Whatever you do, don’t miss out on our $50 off Lumen discount code RYANANDALEX and give it a few weeks for the device to “learn” your body.

Good luck! Once your Lumen comes in the mail, feel free to reach out to us for support. For more helpful resources, such as our Bodyweight Workout Plan or the zero calorie foods list, head over to our Weight Loss page.

The weight loss bundle ryan and alex duo life

Our Proven Weight Loss Bundle

As engineers, we know this to be true:

1. What gets measured, gets improved.
2. If you fail to plan, plan to fail.

So, as health coaches who want you to succeed, we bring your our best programs, trackers, and cheatsheets to monitor progress and achieve your weight loss goals.

Instantly download the bundle and we're always here for support.

As Seen In Feature Bar Ryan and Alex Duo Life

Hey we're Ryan and Alex

The creators of Ryan and Alex Duo Life. We are a husband-wife duo and “lifestyle engineers.”

After eight years working in the corporate world as engineers, we left our high-powered jobs to tackle our true passion — helping couples engineer their best lives.

The synergy of our engineering minds and ten years of health coaching experience produced Ryan and Alex Duo Life. Our mission is to help you transform your bodies, minds, and relationship as a couple.

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