Can You Truly See If You're Burning Fats Or Carbs?

picture of lucas

Lucas Aoun

Founder @ BYB

October 12, 2021

What if you could directly see whether you're burning fats or carbs? Introducing the Lumen. Lumen measures your FAT and CARB burn. How well you burn fat is essential to helping you lose weight and critical to becoming a good endurance athlete. Lumen gives real time feedback on your current metabolic state. After 4 days of readings, Lumen mostly knows your breath signature and how it varies through key events in your day.

Key Facts

The Lumen ‘breathalyser’ is simple to use and for each rested, check-in breath you will usually need one reading plus a verification reading, taking a minute to complete both and ‘tag’ the result in the app.

This is important, new information to all of us.

You might have previously counted your consumption of carbs and calories or you might have looked at your fitness watch to see estimations of fat/carb/calorie usage based on effort levels but it's been difficult to determine your body’s true ability to burn fat at any specific times of the day.

Lumen can determine that.

The smartphone app that is free to download is also sleek and sexy.

Based off my own breaths it ‘feels’ like it’s broadly correct based on my experience with it. Perhaps more importantly, Lumen gives information that is actionable and guided – the readings MEAN something and the Lumen app suggests exactly what you need to do about it.

How the Lumen Works 

The Lumen uses your breath, sometimes one breath and sometimes two, to analyze the CO2 you are putting out.  This allows the device to determine if your metabolism is burning fat, carbohydrates or a mix of the two.  When your CO2 is high, that signals that you are using more carbohydrates.  When your CO2 is low, it means you are burning more fat.

The device gives you a score ranging from one to five after each test.  If your goal is to burn fat, the ideal reading is a one or a two in the morning when you wake up.  This means that during the night your body used all of the carbohydrates that you ate the night before.  Carbohydrates are the easiest fuel for your body to burn and your body uses them first.  

Me with my Lumen!

What Is the Science Behind Lumen?

The lumen was tested for accuracy against a blood test and the gold standard metabolic cart RER.  

If you are asking yourself, as I did, what the heck is a “metabolic cart RER?”  RER stands for respiratory exchange ratio.  It is a measure of your CO2 output using a device that goes over your entire face.  This device captures data from your breath and sends it to a computer that you are tethered to.  It is not something that can be easily done at home, it is typically used in a doctor’s office.

The Lumen can give you the same information at home that you could previously only get in a doctor’s office with amazing accuracy.  

I like that Lumen has education modules, presented sort of like social media stories, that taught me about metabolism, diet, and food. They were comprehensible and as easy to consume as delicious, delicious carbs — except they were about topics like how exercise affects your metabolism. While the main time to use Lumen is first thing in the morning, Lumen also encourages users to get their Lumen score before a workout, to help determine if they’re sufficiently fueled up. Then, 30 minutes after a workout, you can take your Lumen score again to see how running, weightlifting, or yoga affected your metabolism. Seeing my score decline after a hard workout was gratifying.

Is The Lumen Worth It?

I do find the information it gives me useful.  It’s a great tool if you practice intermittent fasting and like to experiment. I think it’s a far more enticing tool than using a ketone/glucose monitor which requires a lot of finger pricking.  

The website has lots of resources if you want to dig deeper on how to use it.

If you want to purchase the Lumen for self experimentation,  you can use the code ergogenic10 for 10% off here


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