This new tech could make your fitness tracker obselete.

By Julia Malacoff
August 16, 2018

When it comes to weight loss, metabolism is a hot topic. It's pretty common to hear people say that the reason they're struggling is a slow metabolism, for example. That's why fitness trackers can be so immensely helpful to those who are trying to figure out how many calories they burn in a day. (Related: I Tried the Fanciest Fitness Tracker On the Market)

But what if you could find out how many calories you're burning, plus how much and what types of food you should eat, in an instant? That's what Lumen-a new device and app that measures your metabolism through breath-promises. Before you get too excited: It's not available yet. Lumen is being crowdfunded on Indiegogo and is set to launch in March or April of 2019. (BTW, here's everything you need to know about biohacking your body.)

Here's how it works: You breathe into the Lumen, a breathalyzer-like device, which is connected to an app on your phone. The device analyzes the CO2 content of your breath to tell you whether you're burning carbs or body fat for energy. This is used as the basis for personalized nutrition recommendations, including the number of carbs and fat you should be eating on any given day based on your goals.


Photos: Lumen

This feature may be of special interest to those who are on the keto diet, which focuses on getting the body into ketosis, a state where it's burning fat for fuel. Because Lumen can tell you quickly whether you're burning body fat, you can easily check whether you're staying on track. As of now, the app doesn't provide keto-specific meal recommendations, but it's still a pretty good alternative to straight-up guessing or testing your urine for ketones.

Lumen doesn't just tell you what to eat but also tells you why certain changes may be happening in your body. For example, if you gained weight overnight, it can tell you that it's probably because of excess water and glycogen stores from eating a lot of carbs the day before. If you're low on energy, it can tell you that you haven't had enough carbs, which could be making you feel tired.

The device is being marketed as a *sustainable* way to lose weight, maintain weight loss, and improve sports performance. Rather than promising fast results (like a fad diet), it promises results that will last. (See: What Fad Diets Are Doing to Your Health.)

If this sounds too good to be true, well, it might be. Though the device is not available for use yet, we talked to some weight-loss experts to get their take on whether it's something worth trying.


One solid perk: It's always a good idea to see how your body functions on your current diet before moving forward with any nutrition changes, says Gabrielle Mancella, a registered dietitian and Ph.D. candidate at the University of North Florida. And the CO2-measuring system is actually a pretty well-accepted tool for metabolism tracking among dietitians. "This allows us to personalize your plan with intention and analyze your results based on highly accurate outcomes such as CO2 production and body composition versus a number on a scale or BMI," she says.

In other words, this device could provide an accurate starting point, rather than forcing people to simply guess how they should change their diet. Plus, it could help take the focus off of things that are typically discouraging, like the number on the scale, she says. "Guiding people away from the long-standing attachment to the scale and redirecting them to focus inward or on performance is not only a more positive outlook but definitely more rewarding in terms of outcomes and measuring progress," adds Mancella. (That's one very important way to make a health transformation last.)

That being said, you shouldn't put all your weight-loss faith in this one device. "Metabolism is important for weight loss, and whether you're burning fat or carbohydrates will determine weight loss. Your goal for weight loss is lipolysis, which is the biological process of breaking down fat in the body-so, yes it does have a meaningful impact. However, metabolism seems too complex to determine from a single breath since hormones, enzymes, and biological reactions are all intertwined," says Jackie Arnett Elnahar, R.D., a registered dietitian with TelaDietitian. (Here's more on the science of burning fat.)

And while metabolism matters, the most important factor in weight loss or maintenance is the food you eat, explains Ved Gossain, M.D., an endocrinologist at Michigan State University. "Ultimately, weight gain or weight loss is determined by calorie intake and calories expended," he says.

So if this device successfully helps you alter your calorie intake, then yes, it might work for you. But will knowing your ideal calorie intake translate into a change in your weight? Only if you actually stick to the advice the app gives you. And of course, since the product isn't available to test yet, it's hard to know how accurate it is, but it certainly does seem promising.