Lumen Review

Any links to online stores should be assumed to be affiliates. The company or PR agency provides all or most review samples. They have no control over my content, and I provide my honest opinion.

Lumen claims to be the world’s first hand-held, portable device to measure metabolism accurately. The homepage even states that you can “hack your metabolism” and then “enhance fat burn, lose weight & boost energy naturally.”

With such grand claims, you may be wondering why Lumen is not a household name. Surely everyone that has the slightest interest in health and fitness would benefit from such advanced insight into their metabolism?

While the Lumen is very good and, I imagine, genuinely useful for many people, it is not quite the revolutionary piece of tech it might sound like.


lumen large rectangle 336x280 1
  • On the spot testing of your current metabolism/level of fat burning
  • Real-time daily metabolic insights
  • Nutritional advance based on your readings and overall goals
  • Fat focussed (but not Keto) nutritional plans that help optimise your body’s ability to burn carbs and avoid blood sugar spikes by improving your metabolic flexibility.
  • The fat focussed diet promotes you body to burn fat which decreases your hunger levels and makes your body less dependent on snacking.
  • Feedback on your metabolic flexibility and how to improve it, which has a preventive effect against obesity, diabetes, and other metabolic diseases.
  • Meal ideas/plans that work with the nutritional advice given

Set-Up & Taking Measurements

Setting the Lumen up is quite easy. Both the device and app have been well designed and are quite user friendly.

The app auto detects the Lumen, so there is no faffing around with pairing things. You will then need to go through some basic questions about your goals and your diet. Finally, you will be taught how to use the Lumen.

 Taking the measurements is quite easy, but it does get laborious doing it multiple times per day.

  • You need to exhale fully
  • Breathe in through the Lumen, expanding the circle in the app to the middle circle
  • Hold your breath and remove the Lumen away from your
  • When the countdown reaches two, bring it back to your mouth and exhale through the Lumen at a relatively firm but consistent rate, keeping the indicator as central as possible.

More often than not, you will have to take two readings with a 30-second gap between the reading. I found that some of the morning readings required just one breathe.

You can’t take a reading if you have been moving around too much. You need to be sat and relaxed. You can’t take a reading within 30 mins of finishing exercise.

So it is easy to use but a lot to remember.

In Use

Lumen Review5 1

I started using the Lumen in the weeks running up to the Chester Marathon, which was either convenient or bad timing, I am not sure.

I used the Lumen to help provide me insight into my fat burning/metabolism, and it worked well for this. However, it was too close to the marathon for me to start messing around with my diet. I wouldn’t say my diet is particularily well optimised, but I know how I perform on what I currently eat. When I reviewed Love Yourself meals, my performance dropped off significantly for my long run as I just didn’t have enough calories the day prior, so I had no intention of doing this again.

Day to day, I intermittent fast. I am not some intermittent fasting zealot that claims you will shed fat with ease, I just don’t really like breakfast and find eating it either makes more sleepy and/or more hungry. As an ex fat guy, I still like big meals, so a big lunch and dinner works well for me.

To make the most of the Lumen, you need to take multiple readings per day. This is one of the biggest issues Lumen has. It requires quite a lot of discipline to remember to repeatedly take these readings. In theory, you could be taking readings for the morning, pre & post-exercise, pre-lunch/post fast, post-lunch, pre-dinner, post-dinner and pre-bedtime readings. I doubt many people do that, but I would guess 3 readings per day is ideal, and the more, the better, at least until you have an understanding of your body and the nutrition plans.

Start the day – Nutrition planning

This seems to be the most important reading of the day. With this, you will build up your nutritional plan.

For my profile, I opted for fitness performance, and it looks like I selected the increased muscle mass option when it came down to protein (2g per Kg). Endurance probably would have been better at 1.8g per Kg.

As I write this, my morning plan consists of

  • 225g carbs (900 calories)
  • 182g fat (1638 calories)
  • 165g protein (660 calories)

This provides a total of 3138 calories. I typically eat a minimum of 3500 calories which is why I had no plan to follow the nutritional advice just before my marathon.

As you can see, it is a very fat focused nutritional plan which sacrifices carbs. I am more of a high carb person, so it would take a lot of adjustments to follow this plan. With 3138 calories, I could probably lose some of my wobbly bits without sacrificing too much muscle.

Pre and Post Exercise Measurements

Lumen Review4

When you take a reading before exercise, the Lumen app will again provide you with some nutritional advice, saying how many servings of carbs you can have.

Again, I didn’t really follow this. For day to day fitness, I prefer doing things fasted as I find that for short intense or for cardio under an hour, I perform better fasted. Thanks to Lumen, it motivated me to stick to this. If I have a hunger pang, it is sometimes a little too easy to pick up a granola bar or something.

Insconistances & How to Avoid Them

My post-exercise readings rarely gave the results I was expecting. I think it is possible this is a user error. I almost always wake up and get a pre-exercise readings of 2, but my post-exercise reading has quite frequently been 3. This doesn’t make a lot of sense with fasted cardio.  

The most likely cause of this is me taking the reading too close to finishing exercise. I have a very particular routine, so once I am out of my gym and showered, I make lunch and take the reading just before eating. It is possible this is under 30 mins.

Poor breath samples can also affect the reading. You want to clear your lungs before you breathe in. Then also provide a consistent breath during the reading.

Another possibility is that by the time I take this reading, I have fasted for nearly 18 hours and completed fasted cardio. It is possible I am in a state of ketosis, which seems to cause inaccurate measures. Though, I don’t think it is that easy to enter ketosis.

On one occasion, I woke up with a Lumen reading of 1, post exercise, it was 4. This was unusual enough that 10 minutes later, I took another reading, and I was back down to 1. This is clearly a faulty sample, it was likely that I am at fault, but it does seem that the Lumen is prone to these inaccuracies.

My Results

My chronically boring and militant routine meant that after a few days, it was quite easy to predict the readings I would get. I consistently wake up with a lumen reading of 2. Which I was happy about as I eat about three times the amount of carbs Lumen recommends.

On the day of my marathon, I woke up with a lumen reading of 4. This was a predictable reading but it was good to see, both for my run, but also showing that the Lumen was at least roughly accurate for identifying when I am burning a lot of carbs. I also got an easy PB, so I was doing something right.

Price and Alternative Options

Lumen is not cheap. It is subscription-based and the cost of the device is built into the reoccurring price you pay.

  • The 6 month option is £249, then £19pcm. For 1 year this works out as £363, and for 2 years this is £591
  • 12 months is £259 this renews at the same price, so £518 for 2 years
  • 18 months is £349; again this would renew at the full price.

You can buy Lumen here

Perhaps the biggest selling point of Lumen is the fact it has almost no competition.

Breezing is a similar idea to Lumen but with O2 and CO2 measurements. It looks less user friendly and you have to send and order form off for the price, so I would expect it to cost a lot.

Foodmarble Aire is designed to find the foods that work for your digestive system by measuring hydrogen levels on your breath. So it is less performance-related and more focused on improving your  digestive health

Supersapiens is a bit more performance focussed rather than diet, this provides real-time glucose measurements using the same sort of patch diabetics wear. It is quite expensive, and the biosensor has a needle that penetrates your skin, so a bit less appealing than a breath reading, but it takes readings 24/7 without you doing anything.

The cheapest alternative would be to take blood glucose/ketone tests manually and use your own judgement, but this would require the knowledge to make decisions based on the results you get.


With little to no direct competition, the Lumen is uniquely equipped to offer insight into your metabolism and provide nutritional advice based on the results.

This sort of feedback is genuinely useful for anyone interested in optimising their diet and fitness. Previously you had to just guess and assume the information you read online about fasting, carbs, or whatever was accurate.

However, all this comes at a cost, both the physical cost of the device and the time commitment you use it.

At £259 for the year, this is quite expensive. You then need to commit to taking multiple readings per day, and ideally, you want to stick to the nutritional advice.

For fit people that have a decent understanding of nutrition and perhaps already practice things like fasting, the end result can be getting a lot of readings which you already expected.

Even though the daily readings were predictable for me, it did motivate me to stick to my usual intermittent fasting schedule.

This seems like it would be a good investment for people on two ends of the spectrum, rather than someone like me floating around in the middle. It could be good for people just getting into nutrition and fitness and want some sort of intelligent feedback on their diet.

Or, for people that are a bit more serious about performance than myself and want to dial in their nutrition as much as possible.

Lumen Review Rating


Lumen is a unique non-invasive way to gain some insight into your current levels of fat and carb-burning. It will then guide you with an optimised nutrition plan designed to maximise fat burning and reduce hunger/cravings.

On paper, this should appeal to literally everyone. Who doesn’t want real-time insight into their metabolism with diet recommendations based on this? It doesn’t matter if you are fat, thin, just getting into fitness or an elite athlete. This should help you understand how your body works like no other device.

The device does seem to genuinely work as they claim, and the data provided will be useful for most people. However, it is quite expensive and requires a lot of discipline to take multiple readings per day. Depending on your knowledge of nutrition and fitness, the results can be quite predictable, but it can also have some inconsistent results due to either user error or the weird ways our bodies work.

The end result is an excellent innovative device, but I don’t think it has quite the mass appeal as I was expecting. People obsessed with optimising their diet or people just getting into nutrition and fitness should like it, but I think the people in the middle that are not going to put the effort into it may start with the best of intentions and quickly find they don’t use it all that much.

  • Overall - 75%


  • A unique none invasive way to get insight into your current fat/carb burning
  • Quite easy to use 
  • Customised nutrition plan based on goals, your activities that day and your Lumen readings
  • Meal ideas that work with the Lumen recommendations 
  • Fat based approach aims to improve metabolic flexibility, increase fat loss and reduce cravings. Something that would appeal to the vast majority of people
  • Has a Garmin CIQ widget


  • Reasonably expensive
  • Time consuming and requires quite a lot of commitment 
  • Can be prone to inaccuracies due to user error or other reasons. 

Similar Posts

One Comment

  1. This is an excellent review. Many thanks.
    I think the price point means it is probably not for me but it is an interesting concept.

Leave a Reply

Your email address will not be published. Required fields are marked *