In the ever-evolving landscape of dieting and fitness, the Lumen device emerges as a novel approach, distinct from traditional diets, fitness regimens, glucose monitors, or heart rate trackers. Lumen is a breathalyzer designed to analyze whether your body is burning fat or carbs. The company asserts that understanding this process allows users to comprehend their metabolic flexibility, which can be leveraged to supplement weight loss, enhance fitness, and optimize bodily functions.
What is Lumen and How Does It Work?
Lumen is a subscription-based device and app combination that analyzes breath samples for CO2 levels throughout the day. The device transmits recorded data to the app, which processes the numbers to determine whether the body is burning carbs or fat. Traditionally, CO2 breath level measurement devices were exclusive to laboratory or medical settings due to their high cost.
To understand how the Lumen device harnesses the tenets of metabolic science, it's important to know that Lumen measures metabolism/metabolic rate based on the concentration of carbon dioxide (CO2) in your breath. The higher your CO2 concentration, the more you are burning carbs for fuel, because when your cells metabolize carbs, they produce more CO2 compared to when they metabolize fat.
If you went in for a professional lab test to have your metabolism measured, you would get back your Respiratory Exchange Ratio (RER), which is the amount of CO2 exhaled divided by the amount of oxygen (O2) inhaled. That number ultimately lets you know your metabolic efficiency. Lumen allows you to get your RER anytime you want by breathing into your Lumen, no lab test required. A high CO2 reading means you’re burning carbs, a low CO2 number indicates you’re torching fat.
Getting Started with Lumen
The small square starter box comes with the Lumen device, its docking station, a USB cable for charging, a travel pouch, and the Lumen App Getting Started Guide. The written “directions” included with the Lumen are pretty paltry, but the Lumen app is an integral step for using the Lumen. You have to begin by creating an account and then answering a battery of lifestyle and physiology questions. During the setup process, you are asked to input things like height and current weight but also estimated hours of sleep and daily exercise habits. It is possible to link Lumen to your Apple Health, Google Fit, or Garmin IQ account if you have one. Once all your basic data has been collected, you have to select your track. There are three options: Metabolic Health, Fitness Performance, and Healthy Weight Loss. The app also allows women to track their monthly cycles, which could be great information to have when examining metabolic shifts.
Read also: Comprehensive Lumen Review
The Lumen Device: Design and Functionality
Once the Lumen is fully charged, pairing it with the Lumen app is simple via Bluetooth. The device is about the size of a thick Sharpie marker and doesn’t weigh much. It is light while still encasing a pressure sensor and a CO2 sensor within its ergonomic casing. To keep your Lumen clean, wipe down the metallic mouthpiece with an antibacterial wipe.
Breathing Technique and Daily Measurements
In the app, a “breathing” tutorial guides users through the process: inhale for 10 seconds, hold your breath for 10 seconds, and then exhale for 10 seconds. This may need to be done twice to get an accurate reading, waiting 15 seconds between each test. The app has a helpful little bouncing ball you are coached to get in the center of a circle to make sure you’re not breathing too hard, too soft, or too fast. Once you start breathing into your Lumen at regular intervals, each time you take a reading you’ll be given an assigned “score” on a five-point scale. That number tells you whether you’re burning mostly fat (1, 2), mostly carbs (4, 5), or carbs and fat (3). Once you take your morning measurement (which should happen before you eat or drink anything), predicated on your goals, the app will also give you an assignment of a low-carb, medium-carb, or high-carb day. It comes with recommendations for the maximum number of grams you should ingest of carbs, protein, and fat-your macros - for that day.
The Importance of Metabolic Flexibility
The ultimate goal of Lumen users is to achieve “metabolic flexibility,” a term coined by the company that basically means your metabolism becomes more efficient at burning fat and not just carbs for energy. If you’re in the Lumen fat-burning mode more often, they claim it becomes easier to lose weight and stay lean. Just like your muscles become fitter with regular workouts, apparently so does your metabolism if you pay attention to how your body switches between burning carbs and fats.
Lumen's Cost and Commitment
You get the Lumen device for “free” along with your paid subscription. Pricing is as follows: 6-Month “Metabolism Booster” = $249, 12-Month “Advanced Fat Burn” = $299, 18-Month “Optimal Health” Track = $349. There is a 30-day money-back guarantee and a 1-year warranty on the device.
To get the most out of Lumen, you will need to breathe into the device before your first meal, after each meal, before any exercise sessions, after any exercise sessions, and before going to sleep at night. You’ll also need to log the food you eat into the app, which I’ve also noted isn’t the most pleasant or smoothest experience, and frequently check for updates on your breath scores. To use Lumen correctly is to make it a part of your day-to-day life as sleep, meals, and exercises are. It will feel tedious at times. You will groan about it. When it says you’re due for a low-carb day, you need to hit the suggested carb, fat, and protein macros.
Read also: Achieve Weight Loss with CrossFit
Flex Score: Measuring Metabolic Flexibility
It’s going to take two weeks of consistent measurements before you get your first Flex Score. By Lumen’s definition, your Flex Score is a number between 0-21 that tells you how well your body is working with what you’re putting in your mouth, and also what your metabolic flexibility is at this juncture.
Accountability and Dietary Adjustments
Lumen makes you more aware of what you’re eating and how it’s affecting your body. That means keeping a detailed food log, recording every minute you work out, updating your weight, watching how many hours you sleep, etc. And it’s a lot of work. Lumen absolutely makes you pay attention to what you’re eating, how much you’re eating, and how the timing affects your metabolism. Lumen definitely encourages intermittent fasting. Though not a keto program (because they believe you sometimes do need carbs to keep your metabolism “guessing” and not storing them), it also seems to heavily lean towards a prescription for low-carb eating - at least if weight loss is your selected track. Also, to get your most accurate readings, you’re supposed to enter every gram you eat at every meal of each macro (which you have to do manually). Not paying attention to their macro suggestions will absolutely influence your “score” and subsequent daily recommendations.
Does Lumen Work? Scientific Validity and User Experiences
Lumen says its validity as a metabolism measuring device has been reaffirmed by a San Francisco State University study. The technology is new, it does what it says it does, and the brand doesn’t make grandiose claims. This might be because you have to invest a serious amount of time into Lumen for its potential to shine through.
The Lumen is one “piece” of an overall program. This machine is the first portable metabolism measurement device on the market, and it seems to have a reasonable degree of accuracy. But if you want to lose weight and not just to see how your body is burning what you eat, then you’ve got to commit to the whole program. That includes taking breath tests several times a day.
Lumen tests your body's carbon dioxide levels to determine if your body is in fat or carb-burning mode. Based on your daily results, the Lumen app gives advice on how to eat and exercise to ensure your body starts the day in fat-burning mode before transitioning to carbs-burning mode. Testing Lumen helped one reviewer understand why she wasn't burning fat, and it helped her tweak her eating habits and lifestyle to finally hit the right balance. In her experience, the science behind Lumen's personalized recommendations really did work. She could see firsthand how each meal affected her metabolism.
Read also: Transformations with Ozempic
Who Should Try Lumen?
After testing the Lumen metabolism tracker for six months, one reviewer believes it's a great (noninvasive!) tool for just about anyone. Whether your goal is to lose weight or to optimize your workout results, the Lumen can help shed light on what's going on in your body.
That said, Lumen is not suitable for anyone who is: Under the age of 16, women who are pregnant or exclusively breastfeeding, has a history of eating disorders, has diabetes, has severe asthma, has Chronic obstructive pulmonary disease (COPD).
Potential Downsides and Considerations
The Price: the device itself is a one-time fee of $250-300 depending on where you purchase it, along with a mandatory monthly subscription of $19 per month to take advantage of the integrative app features.
The Commitment: in order for this to work well, you need to commit to daily breath tests and diligent food record keeping. Otherwise, you won’t have enough data to determine how to change up your eating habits to maximize results.
The Reality: although the technology is sound and sensible, this might not be the answer for everyone - keep in mind, breathing into a device on the daily won’t necessarily help you stop emotional/stress eating, find motivation/time to meal plan and manage hunger and craving cues. Further, if the device tells you you’re burning more fat that doesn’t necessarily mean you’re burning actual BODY FAT. It could just mean you’re burning more fat from food you eat. For true weight reduction, you need to eat less calories than you expend. Finally, many might also find the detailed data tracking to be triggering and stressful, contributing to additional food noise and complicating your relationship with food.
Lumen and Metabolic Flexibility: A Deeper Look
Lumen claims that its program helps you “hack your metabolism.” This premise hinges on the concept of metabolic flexibility, which is the body’s ability to efficiently switch between burning mostly fat when fasting, at rest, or engaging in low-intensity activity or prolonged exercise, and burning mostly carbohydrates after eating or higher-intensity exercise.
Some studies suggest that people with obesity or type 2 diabetes have reduced metabolic flexibility, meaning their bodies are sluggish in shifting between fuel sources. That could mean, for example, that after you eat a meal your body struggles to turn the carbs you ate into fuel, which could result in prolonged high blood sugar levels.
But it’s not clear that knowing how metabolically flexible you are adds much insight into your health. Part of the problem is a classic chicken-and-egg conundrum. Metabolic inflexibility often occurs hand-in-hand with insulin resistance (difficulty moving sugar from your blood into cells). But it’s not clear if metabolic inflexibility causes insulin resistance…or if it’s the other way around.
Some researchers suggest that signs of metabolic inflexibility may precede markers of worsening metabolic health like high blood sugar and insulin resistance, but more research is needed to flesh that out. What’s more, there is no single test that captures metabolic flexibility. Nor is there an agreed-upon threshold that signals when someone has crossed into “inflexible” territory. And many studies measure and define metabolic flexibility differently, making it challenging to compare their results. All of that makes us suspicious of Lumen’s “Flex score,” which claims to tell users how metabolically flexible they are.
Alternatives to Lumen
As an alternative, one expert offers a similar test through a device called the Korr Reevue machine. Like Lumen, it uses indirect calorimetry, or analysis of gas exchange through a breath test.