Lumen Review in 2024 (Increasing Metabolic Flexibility)

This is my review of the Lumen metabolism tracker. My goal was to use Lumen for weight loss, and it helped me to lose 15 pounds over three months.

Lumen is like a personal nutritionist in your pocket, but it works only if you religiously follow it. In this Lumen review, I will analyze the experience, its accuracy, drawbacks, and alternatives.

Let’s get started!

• What is Lumen
• How does it work
• Accuracy
• How to use
• App
• Price
• Drawbacks
• Who is it for
• Alternatives

What is Lumen?

Lumen is a hand-held, portable device to accurately measure metabolism. Lumen tracks, analyzes, and shows you how to improve your metabolic health.

What makes it so unique is that this type of metabolic testing was previously only available in medical settings and for high-level athletes. Now you can fit it into your pocket.

It uses a CO2 sensor to determine the concentration of carbon dioxide in your breath, indicating whether your body is burning fat or carbs. 

This helps you understand your metabolism, improve metabolic flexibility, and, in turn, lose weight and get better sleep.

Lumen was created by twin sisters, both ultra-marathon runners, who wanted a quicker and simpler way to track their metabolism on the go. 

Definition: Metabolic flexibility refers to the body’s capability to efficiently switch between using different energy sources, like fats and carbohydrates, in response to changing energy demands and dietary intake. It signifies adaptability in energy metabolism. (1)

Lumen showed me my body’s carb tolerance without being deeply in ketosis. Basically, how much carbs my body tolerates while still burning fats. On some training days, I was still burning fat even while eating over 100 grams of carbs.

Pros

• Provides consistently accurate RER measurements
• Mainly suggests a low-carb eating style (best keto alternative)
• You learn a LOT about your metabolism
• You actually lose weight if you stick with it
• It feels like having a personal nutritionist (based on your readings)
• 30-day money-back guarantee

Cons

• No device screen, need an app to get a reading
• Must manually enter all foods and exercises daily
• Apple, Google, and Garmin integrations are available with monthly membership

How Does Lumen Work?

You simply breathe into the Lumen sensor and it measures the carbon dioxide (CO2) in your breath. If you have a high level of CO2, it means you’re burning carbs for energy; if it’s low, you’re burning fat. 

Level	Ratio	Energy Source
1	84-100% of fats	Fats
2	63-80% of fats	Mostly fats
3	42-60% of fats	Fats and carbs
4	60-77% of carbs	Mostly carbs
5	80-100% of carbs	Carbs

Lumen’s scientific basis is backed by multiple validation studies, and it’s similar to the gold standard of metabolism measurement, known as the Respiratory Exchange Ratio (RER), which looks at your CO2 to oxygen levels.

Once Lumen learns more about your results, it calibrates its suggestions to your unique CO2 range and lung capacity. It’s super easy to use, too. 

• The device syncs to your Android or iPhone and comes with a neat USB-C that connects to the base station. A full charge can last you up to 14 days. 
• What’s even better, based on your breath readings and all the data it collects, Lumen gives you a list of daily recommendations. 
• It tells you what to eat, how much, what activities to do, and even things to avoid, like bright screens at night. 

I like how premium it feels in my hand, and I especially appreciate the matte black finish. 

How Accurate is Lumen?

Lumen breath analyzer is scientifically validated by multiple peer-reviewed studies conducted by researchers from Purdue University, University of Toronto, and Colorado State University, among others. (2)

Lumen’s internal studies, as well as the San Francisco State University study, suggest that Lumen’s measurements are on par with a traditional RER measurement device. (3)

In my own experience, I say I got fairly consistent results with this metabolism sensor. 

I also do intermittent fasting in the morning, so even if I had a bad meal the day before, my morning lumen reading almost always gives me a reading of 2. 

When I was in ketosis or properly following my low-carb diet, I got reading 1’s pretty consistently. 

How to Use Lumen?

Using the Lumen breathing device is super simple and has become a key part of my daily routine.

Every morning, the first thing I do is grab my Lumen and take a breath test. 

1. I breathe in through the device for 4 seconds
2. Hold my breath for 10 seconds
3. Then, exhale into the device for 6 seconds 

I felt like the breathing intensity into the Lumen sensor was slightly harder than completely comfortable. Once you start breathing out, I feel like I’m not gonna have enough breath to do 6s here, but I actually get there every time.

There’s a handy gauge on the device, a sort of floating ball that you aim to keep in a circle. If it falls out of the circle, you’re either blowing too hard or not hard enough. It’s a fun little feature that helps you get your breathing just right. 

The Lumen app on my phone then gives me feedback about whether I’m burning fat or carbs and provides a customized eating plan for the day. 

I’ve been doing this for the past 12 weeks, and it’s been a breeze. The initial learning curve was small, and the app guided me through it. 

Lumen App

I have had a fairly positive experience using the Lumen app. I downloaded it, connected my device, and answered some questions about my health and lifestyle. 

The app then guided me through a “calibration day” to understand my body’s unique way of metabolizing carbs. 

Now, every morning, I start my day with a calming routine of Lumen breaths, which helps the app track my metabolism and give me a daily score out of five. 

This score helps me understand my body’s nutritional needs for the day. The app also gives dietary advice, whether I should be eating a low, medium, or high-carb diet. 

The Lumen tracker even has a complete food tracking feature, so I don’t need to use myfitnesspal anymore. 

Plus, I love the educational modules that teach me about metabolism and diet. The user experience is straightforward, making it easy to monitor and understand my health and nutrition. 

Here’s what you get from the app:

• Meal Suggestions: Figuring out what to eat can be tricky initially, and I found this incredibly useful.
• Grocery Lists: This simplifies organizing your ingredients effortlessly.
• Serving Size Tips: From “the plate rule” to portion sizing for rice.
• Dining Tips and Tricks: Invaluable when you’re dining out.
• Helpful Resources: It also offers a library of user-friendly videos in categories like device tips, nutrition education, and motivational content for your goals and mindset.

Flex Score

The Flex Score, a term coined by Lumen, is designed as a measure of your body’s metabolic flexibility. It’s a number that falls between 0 and 21, showing how well your body is doing with the food you’re eating. 

Just like a report card, the higher the score, the better. You get a score of 0-6 if your metabolic flexibility is low, 7-14 means it’s average, and if you score between 15-21, your metabolism is doing a great job! 

Now, getting the Flex Score isn’t an overnight thing. It requires patience and consistency. You need to use Lumen and its app for at least two weeks to get your first Flex Score. 

I’m going to be honest, the first two weeks were a bit frustrating with the lack of inf (Flex Score).

Lumen Price

So, how much does Lumen cost? There are two options: the metabolism tracker itself and an optional premium monthly subscription. Here’s what you get. 

Lumen Metabolism Tracker – $299

The Lumen metabolism device is a handy tool that you can get for a one-time fee of $299. This price includes:

• The Lumen device
• A free version of the app
• Unlimited real-time metabolic measurements. 

They also throw in a free month of premium membership, which you can cancel anytime if you don’t want to continue. But if you do decide to go premium, it costs $19 a month. 

PS! You can use the Lumen device without the premium monthly membership!

Premium Monthly Membership – $19/mo

With this subscription, you will get:

• Lifestyle insights and recommendations
• Daily personalized nutrition plan
• Macro-based meal suggestions
• Metabolic coaching and support
• Integrates with Apple Health, Google Fit, Garmin

As I am a heavy iPhone and iWatch user, it really bugs me that you get the Apple health integration with only the premium membership.

But if you’re serious about your health, it could potentially replace your gym membership or other health tool subscriptions. 

Plus, they offer:

• 30-day money-back guarantee
• 1-year warranty
• Free US shipping

So, if you are serious about losing weight, it’s a pretty risk-free way to give it a shot and learn about your metabolism. 

Lumen Drawbacks

For the most part, Lumen is awesome and just works out of the box.

However, during my Lumen metabolism analyzer review, I found several problems that bugged me a lot.

1. No Device Screen

The main issue I have with Lumen is that it doesn’t have a screen on the monitor. This forces me to check my phone first thing in the morning, which I definitely don’t want to do. 

It would be great if there was a small screen on the device itself, making the use of the app optional. With how much I stare at screens all day, I don’t really want another device just for that purpose. 

I feel that a device screen would be a helpful addition, reducing the need for extra screen time, and making the device more user-friendly. 

For example, Biosense has a device screen and it’s very convenient. However, it’s a ketone monitor specifically designed for keto dieters.

2. No “Sick Mode” in App

During my review, I enjoyed some heavy flu and felt like dying. During it, the Lumen app still suggested sticking to a low-carb diet. 

I think it should have a “sick mode” option, recognizing that our bodies might need different nutrients when we’re unwell. It could suggest higher carb intake on sick days and track how our bodies respond. 

After all, being sick often puts us in “survival mode,” where we’re more focused on feeling better than tracking food or sticking to a low-carb diet. 

The app should also take other real-life factors into account, like if we’re stressed or when women are on their period. 

These things can affect our eating habits and workout routines, and having an app that understands and adjusts for them could be more valuable.

3. Food Tracking is Annoying

Keeping track of what I eat should be easy, right? But adding foods to the food diary was really annoying for me. 

For example, there’s no option to add foods to a “favorites” list. I mostly eat the same things, so it’d be useful if I could bookmark them instead of scanning and searching every time. 

Also, the app remembers what I ate yesterday but not what I had a few days ago. That’s just odd. 

Plus, the food tracking logic could use an upgrade. Also, some packaged foods show the wrong info or carb counts. This doesn’t matter for regular users, but for keto dieters, each gram of net carbs counts!

4. App Integrations Are Premium Only

Another issue I’ve found, which might seem small but is a big problem for me, is that app integrations are only available with the premium membership. 

This means you can’t link apps like Apple Health, Google Fit, or Garmin unless you fork over $19 for a membership. 

This is a drawback if you heavily rely on these integrations but don’t want the extra goodies that the membership offers.

Who is Lumen For?

The Lumen breath device is a fantastic tool for anyone who is looking for accountability, data, and structure. But it’s not for everyone.

Lumen is For You

• If you thrive through structure and accountability. If you want data and love state-of-the-art technology. 
• Although it’s marketed as a beginner weight loss tool, I think it’s more like an intermediate self-discovery tool because it requires commitment and consistency.
• You like or have had success with low-carb and ketogenic diets.
• You have struggled to lose weight, or if you have regained those pounds back. I think Lumen would give you the needed insight and actual practical guidance, that perhaps you missed in the past. 

Lumen isn’t For You

• Not ideal for a beginner trying to lose weight for the first time. Then you should get your basics right first, then consider this. Cut out sugars, exercise more, and try intermittent fasting.
• If you don’t enjoy food logging and tracking each detail about your food and health. 
• If you don’t like consistency and commitment. It’s not a magical device; it’s a tool and works only if you put in the effort. 

Lumen Alternatives

Here are the best alternatives to the Lumen breathalyzer based on specific use cases. All of them are good products for doing certain things very well.

1. MyLab Box – Best cheap at-home metabolism test

MyLab Box at-home metabolism test uses finger prick and saliva testing to measure cortisol, testosterone, and thyroid-stimulating hormones. And all of this with a fraction of the price.

2. Biosense – Most accurate keto diet breath meter

Biosense is the most accurate ketone breath analyzer out there. It tells you if you are in ketosis and burning fat for fuel or not. It’s an FDA 1 class medical device and comes with a device screen.

3. Keyto – Best value breath meter for keto dieters

Keyto is also a ketone breath analyzer that measures your acetone levels and costs only $99. The app tells you if you are burning fat or carbs for energy.