Maybe you’ve seen the hype. It concerns a simple handheld device that measures and claims to help you “hack” your metabolism so it can be more “fit” and “flexible”. But what does that even mean? Is your metabolism so easily manipulated? Or is this metabolic measurer just another hunk of junk sold by wellness hucksters?
First, it’s important to understand how your metabolism actually works. Basically, it’s the process that takes the kilojoules you consume and then burns those kilojoules to fuel everything you do, from a brainstorming session to a workout. Fitbit, Whoop, Apple Watch, Garmin – all these trackers use their own algorithms to estimate kilojoules burned on a basic level. But a new device called Lumen claims to reveal what kind of kilojoules — those from fat or those from carbohydrates – your metabolism is burning at any given moment. You simply blow into a Breathalyser-like mouthpiece and, according to the company, Lumen can even tell you how adept your body is at switching between the types of fuel you’re using (known as metabolic flexibility). Not adept? You get an eating plan to help change that, which might change how healthy you are.
Metabolic flexibility is a real thing. A healthy metabolism is always burning a mix of fat and carbs, and the ratio changes depending on factors including how intensely you’re working out (low-intensity exercise primarily uses fat as energy; high-intensity uses more carbs) and whether you’re fasting or in ketosis.
And metabolic inflexibility is also a real thing. Scientific research has linked this metabolic issue to some of the major health challenges of our time, including obesity, diabetes, heart disease and cancer. One cause of metabolic inflexibility: a poor diet. When you’re eating a good mix and amount of foods, your metabolism should be able to process them pretty well. But when you overload your system with too much or possibly even the wrong foods (highly caloric processed foods, mainly), the energy engines of your cells – your mitochondria – start functioning like a deer in the headlights. In the journal Cell, Duke University researcher Deborah Muoio dubs this inflexibility “mitochondrial indecision”. Nutrients get backlogged and jam your metabolism, which can lead to high blood sugar, high triglyceride levels and excess fat around your waist. And all that contributes to the development of those troubling conditions and diseases.
So you can see why Lumen thought it smart to analyse what you’re burning when, give you a score, and then offer diet recommendations to prevent that backlog. Score a 1 and that means your body is fuelling itself mostly on fat, so you should eat more carbs to keep your system from tipping too far in one direction. Score a 5? That means you’re burning mostly carbs and you need some healthy fats to stay flexible. Anything between those two numbers is more of a mix, and you just keep doing you. Michal Mor, a physiologist and one of the founders of Lumen, is thinking far beyond your individual nutritional fine-tuning and says that the data the device tracks can “improve the world’s metabolic health”.
Based on your score, you get a specific eating plan. For example, if you score a 4, you might get a “medium carb” daily plan of 193 grams of fat, 163 grams of protein and 180 carbs. Hitting these precise numbers requires that you measure what you eat, ideally with a food scale. (Which also means you’re most likely going to be eating less
than usual.)
All this sounds great and techy and hackerish and kind of cool: you’re analysing exactly how your eating decisions and lifestyle affect your metabolism in real time. But here’s the thing: It’s not really all that useful. You probably don’t need a $335 Lumen device to improve or maintain your metabolic flexibility. To the extent that you are able to control your metabolism (some portion of metabolic flexibility may be genetic), “the best way to become more metabolically flexible is to be lean and exercise,” says Layne Norton, a nutritional scientist and bodybuilding coach. It doesn’t matter if you become lean by eating carbs or by skewing your diet towards fat. Eating healthier foods or eating less food than you currently do is what helps, and you can do that on your own.
Mor and her twin sister, Merav, who founded the company, came up with the idea for Lumen while training for an Ironman triathlon, as a way to track and test their metabolism to improve performance. They say it helps, but there isn’t much research suggesting chasing metabolic flexibility can enhance cardiovascular performance. But we do know the opposite is true: people who chase fitness performance seem to be less prone to the risk factors for metabolic syndrome (which are also signs of inflexibility), according to a study conducted in Japan. Enter the old chicken-and-egg problem: Is someone healthy because they’re metabolically flexible, or are people metabolically flexible because they’re healthy? Probably the latter, says Norton. Follow basic health advice and your metrics, not just on a Lumen device, will likely get considerably better.
This is why Joseph Reagle, an associate professor at Northeastern University who wrote Hacking Life: Systematized Living and Its Discontents, sees Lumen as simply another device in the sea of health gadgets today. “It’s just this continual churn,” he says. It’s not necessarily a bad thing that people have so many ways to become more engaged with their health. This tracker likely isn’t hurting anyone, he says. “Just taking the step [of using a device] can give people a sense of control and optimism.” So if shiny new tools inspire you to follow basic nutrition and exercise advice, Lumen might help you out. But you can find the right balance in your diet without a fancy Breathalyser, too.
How your breath reveals your metabolism
What it measures
You breathe out more carbon dioxide when you’re burning mostly carbs than you do when burning mostly fat. All carbs means you’re exhaling as much CO2 as oxygen you’re taking in. Lab machines that reveal what fuel you’re burning measure both oxygen and CO2; Lumen estimates fuel usage by CO2 alone.
Behind the numbers
Changing what you eat will shift what you exhale, which can alter the score you see. On this test, you’re aiming for the middle – a mix of both carbs and fat. The theory is that by knowing how your body rolls and adjusting for that, you can train your metabolism to be more flexible over time and avoid issues like obesity and diabetes.
