Review: Lumen’s handheld metabolic breathalyser

Lumen are on a mission to hack your eating habits to improve metabolic flexibility with their handheld breathalyser.

  • Excellent onboarding process and ongoing support
  • Lengthy breathing process that often requires another attempt due to inconsistent results
  • Beautiful product design, lightweight and pleasing to the eye
  • Supporting app is brimming with information and education material
  • Lacks integration with other wearables/fitness apps such as My Fitness Pal or WHOOP


Lumen scorecard

We scored Lumen at 18/25, here’s the low-down:

Lumen claims to be the world’s first hand-held, portable device to accurately measure metabolism. Once the privilege of top athletes, or hospitals and clinics, metabolic testing is now available to everyone.

Over the past weeks, I’ve taken the time to review the beautifully-designed Lumen device to see if I could hack my metabolism. I’ve been following a plant-based vegan diet for over 3 years, exercise regularly and avoid intoxicants (caffeine, drugs and alcohol) but had a relatively weak grasp on my metabolism (other than calorie tracking).

I hoped to end my review of Lumen with a better grasp on my metabolism and some actionable insights that could further improve my chances of general healthspan and Longevity.

Getting started with the Lumen device

From the moment I received my Lumen, downloaded the app and started the process I was impressed. The team have worked exceptionally hard to ensure the user experience is unparalleled.

A Zoom meeting (a standard part of on-boarding for all customers) was arranged with one of the customer experience team – Ben – in which I was taken through a presentation about the device where all of my questions were answered: a great piece of customer service, but also a great way for companies to mitigate downstream customer service (often stupid) questions.

The device itself is light, well-designed, pleasing to the eye and easy to use. The app is where the real magic happens. It is well thought out and offers huge amounts of information.

You are offered your daily suggested carb, fat and protein intake after registering your morning breath (luckily it doesn’t register your morning breath!) and there are a team of nutritionists at hand to answer any questions you have, as well as lots of informative content suggestions.

Lumen’s science

The Lumen device offers its insights through Respiratory Exchange Ratio (RER), this is essentially the sum of CO2 expelled divided by oxygen inhaled. This is a core part of any metabolic assessment that reveals what you are burning, fat or carbs.

Higher ratio = carb burn, while lower ratio = fat burn – pretty simple.
In collaboration with Lumen, a team at San Francisco State University’s exercise Physiology lab conducted a study To evaluate the validity of a novel hand-held device (Lumen®) for measuring metabolic fuel utilization in healthy young adults which “Shows the validity of Lumen® to estimate metabolic fuel utilization in a comparable manner with the “gold-standard” metabolic cart, conveniently providing real-time metabolic information for users anywhere [1].”

Using my Lumen

The Lumen device requires you to take between 2 and 3 breath cycles through the device – breathing in until the circle hits green, holding for 10 seconds and then breathing out steadily until the device tells you to stop. Once this is complete it will give you your score between 1 to 5.

Based on my morning score, and the scores over the past few days, Lumen delivers a daily food plan. This is followed by various videos, pages and educational information in order to shed light on the effects of metabolic flexibility, keto and how to ensure your metabolism is functioning effectively.

Many modern diets are carbohydrate-laden leading to sky-high obesity rates (70% of adults in the United States are overweight), as well as climbing cases of metabolic diseases such as cardiovascular disease, cancer, diabetes and Alzheimer’s.

Low-carb diets such as keto and paleo aim to help the user adopt eating habits that mimic those of our healthier ancestors; these habits improve metabolic flexibility, which is exactly where Lumen says it can help. Giving the user real-time information about how their metabolism is doing, it guides them towards better dietary habits, enabling the body to also leverage fat for energy.

Lumen says

“Lumen provides you with a personal nutrition plan, which contains the amount of protein, carbs, and fat you should eat,” said Michal Mor, PhD, Lumen co-creator. “In order to help you to apply the recommendation, we also provide you with meal inspiration, which you can filter based on your preference, based on your allergy.”

Your intrepid Lumen tester says

Whilst admittedly I wasn’t the strictest with my inputs after every meal and I didn’t read through all of the supplementary information, I found myself acutely aware of what I was consuming and my scores throughout the day had a huge influence on what I ate.

For those that are strict with their diet, optimise for keto and track everything, this is excellent addition to their biohacking arsenal!

For the keto lay-person, it also offers great benefit, in that it not only enlightens you to the wild world of metabolic flexibility but it brings your attention to your diet and how it might be affecting your health and Longevity.

Using my Lumen is part of my everyday regime now. Further information here.
… and breathe.