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I Tried Lumen: The World’s First Handheld Metabolism Tracker

There are three indisputable facts about achieving the “perfect” summer body:

  1. Abs are made in the kitchen
  2. The work starts in winter
  3. Steroids exist for a reason

And while I would never condone the latter, I can relate to the struggle of achieving #gainz before having to take my shirt off in public. No matter how many sit-ups or shoulder presses I do in the gym, the bulk (pun intended) of my transformation will be the result of eating a healthy and well-balanced diet. But portion control is hard, seeing as winter hibernation demands comfort foods like macaroni and cheese, pizza, and mug cakes.
Lumen, the world’s first metabolism tracking device, was served to me in a targeted Facebook ad, so I was not only insulted…

“Me? You think I need this, Zuckerberg?!”

I was also skeptical. Considering it is peddled as the only one of its kind, I was also intrigued, especially after jumping on the insufferable “new year, new me” bandwagon by kicking off 2023 with a high-protein, low-carb diet. If this thing could help me keep any of that motivation going, I was all in.

The Lumen metabolism tracker is handheld and fits easily in a pocket or backpack

What Is Lumen?

Lumen is the first to admit that the science of measuring metabolism isn’t novel, but its handheld device definitely is. Before being available to the masses, only top athletes and hospitals had access to the type of technology that can pinpoint precisely what metabolic phase your body is in, and what the implications are based on the time of day, what you’ve recently eaten, etc.

But Lumen’s portable carbon dioxide sensor doesn’t just tell you if your body is in a fat-burning state, but it also offers personalized meal plans and exercises through its app to capitalize on these moments. This gives users the power to control “metabolic flexibility” and take the guesswork out of what and when they should be doing to optimize weight loss results. It’s a little like a futuristic, handheld diet coach. Their tool is up your alley if you’re very into health metrics and measuring your own physiology.

The product is quite easy to use. After downloading the app and syncing your mobile device to the instrument, you simply remove the cap in the morning, inhale for five seconds, hold your breath for 10, and then exhale for an additional five. A Lumen Flex Score is derived from the carbon dioxide level (the higher the amount, the more your metabolism is working) and is immediately logged to provide an overview of how and when your metabolism operates most efficiently.

$299.00/12 Months $499.00 40% off

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Lumen’s tool uses a CO2 sensor and flow meter to determine CO2 levels in your breath. This level is a good indicator of the type of fuel your body is using to produce energy. Lumen is purchased along with a monthly subscription for the app, on which you can view all of your data. This subscription starts at $249 for a 6-month track or they’re currently offering 40% off a 12-month track for new members starting at $299.

The habit was easy to develop and became a normal part of my daily routine pretty quickly. Mornings that started with fasted cardio were met with lower Lumen Flex Scores, and I felt an extra surge of motivation knowing breakfast was going to practically evaporate as soon as it entered my body. I even lost five pounds in less than two weeks.

That said, I do think that achieving a “high-fat burning” state became a bit of an obsession. It wasn’t reaching eating disorder levels, but I was focused on it and it’s something to keep in mind if numbers can become a bit of a fixation for you. A hybrid of fat and carb-burning is ideal for weight loss, but there’s such a thing as becoming too metric-focused on a health journey, and Lumen could get you there if you already lean in that direction.

The Lumen comes with a convenient carrying case Joey Skladany | SPY

The reality is that this is a useful tool for those who have enough discipline to use it but won’t become obsessed. Lumen is a great guide for beginners looking for nutrition guidance, though I only used it about 10 percent of the time and stuck to my tried-and-true, bodybuilder-esque diet that guarantees quick results.

While I’m sure there would have been benefits to following the app’s exact diet plans and workout recommendations, it just didn’t appeal to me — I was scared to try something new. Plus, it’s a real pain in the ass to log sleep, meals, and exercise all at once.

Ultimately, I do think this is a wonderful device for someone less rigid in pre-existing diet and workout routines (perhaps for the guy who has developed that “I’m willing to try anything” attitude). Give it a shot and you may just be pleasantly surprised.


  • Motivates you to be in a fat-burning state
  • Practically idiot-proof
  • Small and compact design
  • Impressive technology that isn’t usually available to all


  • While the device is free, memberships (a.k.a “tracks”) can be quite pricey
  • Sometimes you can’t help but question the science

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