Our Senior Editor tried the Lumen Metabolism Booster to see if it really works

lumen review
Our Senior Editor tried a Lumen Metabolism Booster.

Here at Women's Health we're always up for trying out the latest and greatest health and fitness innovations, so when we saw Black Lively's PT, Don Saladino, recommend the Lumen device we knew we had to try this one out for ourselves.

Don has trained a plethora of huge celebs including Emily Blunt, Anne Hathaway and Blake Lively, and he swears by the Lumen for improving metabolic flexibility, and says its particularly good for clients with a fat loss goal.

The tiny device claims to be able to 'hack your metabolism' and give you tips that will help you tweak your diet to help you improve your metabolic flexibility. To see this tiny device is all it's cracked up to be Women's Health Senior Editor, Roisin Dervish-O'Kane, put it to the test over the course of a month.

What is the Lumen?

The world's first hand-held device that measures metabolism by measuring the CO2 levels in your breath to see if your body is using fat or carbs for fuel.

By understanding your main source of energy Lumen uses these measurements to give you a flex score, which is essentially how flexible your metabolism is. Once you have your score, Lumen will give you tips on how to improve your score and boost your metabolism over time.

This is no quick fix, however, and it does take a few weeks to reap the benefits of this device.

Lumen full review

A vape-like device designed by PHD-having, Ironman-doing twins purports to 'hack your metabolism' to help you make dietary choices more beneficial to your goals.

I'm not one of life’s natural trackers - years lost to obsessive calorie counting saw to that. But after health habits went awry during the lockdown trilogy, I'm open to welcoming data to inform new ones. According to a new gadget generating buzz - the metabolism ‘hacking’ device, Lumen - the key metric to look to for better health is something called metabolic flexibility.

‘This refers to your body’s ability to react to different metabolic challenges,’ says Lumen coach Ryan Saraco on our intro call. ‘The more metabolically flexible someone is, the more effectively their body will process sugar, burning it - rather than storing it.’ Intriguing.

The Lumen is a small, vape-like device, into which you exhale a controlled amount of air - breathing guided by the accompanying app. The gadget's ‘sensor and flow’ meter measures the carbon dioxide concentration in your breath and, from that, determines if your body's primarily burning fat or carbohydrates. Seems far-fetched to decipher that from breath, but a validation study from San Francisco State University found Lumen's nous comparable to in-lab respiratory exchange ratio (RER) tests.

A morning level of one or two - indicating the body is burning fat - is ideal, while a four or five indicates you’re still processing food from the day before. From there, Lumen pulls in my Apple Watch health data - steps, sleep, menstrual cycle - before suggesting a rough nutritional balance for the day.

‘Wake up using mostly carbs for energy and you’ll be directed towards a lower-carb day,’ adds Saraco. ‘But this isn’t about cutting carbs - Lumen will suggest medium and higher-carb days once you’ve been in a fat-burning state for a while.’ There are recipe suggestions (pretty but too fussy for me), accessible metabolic health tips and live in-app support.

After two weeks of morning measurements, and several more throughout the day (time consuming; bit irksome) I receive my Lumen Flex score: a lowly 6.1 out of 21 – indicating that I’m not especially metabolically flexible. Sad. ‘Metabolic flexibility is just one indication that your body is running healthily,’ Gareth Wallis, professor of exercise metabolism and nutrition at the University of Birmingham reassures me. ‘Use the score as motivation to increase what is proven to improve it: working out regularly and consistently. But if you're at a healthy weight and able to perform, physically and mentally, don't stress about it.'

Does Lumen work

After just under a month of four-times-a-week 75-minute yoga sessions my flex score has improved, albeit nominally. I’m sticking with morning measurements; roughly aligning my daily fare to Lumen’s low/medium/high-carb recommendations; still feeling satisfied after a post-workout measurement reveals how the session revved my engine's fat-burning capacity.

The small back-pats for making healthy choices, without too many numbers, work quite well for me. But I reckon you’d get more from Lumen’s offering (plus your not-insignificant financial investment) if you have a specific performance or weight loss goal in mind.

Overall rating:

  • Research-backed: 8/10

  • Value-for-money: 7/10

  • Easy-to-use: 6/10

  • Quick results: 4/10

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