At first glance, the Lumen looks a bit similar to a breathalyzer — at the top, there’s a mouth-piece to breathe into in order to populate results. Every morning, you’ll take a breath into the device and the companion app will you show you information like your daily goal for carb consumption, along with meal and snack recommendations. To help keep you on track, the Lumen app comes with a “food search” feature that allows you to look up certain foods to find out how many carbs each contains. For additional help, the app allows you to submit photos of your meals to nutritionists for feedback in order to get an expert opinion. But how does it work, exactly? The Lumen uses Respiratory Exchange Ratio, which is the preferred method for determining metabolic fuel. By taking a single breath, the Lumen measures the carbon dioxide production and oxygen uptake of a user’s breath in order to calculate how much energy is being burned from carbohydrates or fat. \t \t From there, the Lumen curates a personalized plan for you to follow without having to constantly log your food intake or activity each day. Using artificial intelligence that adapts to your nutritional patterns and behavior, the device is meant to teach you about your body — specifically carbohydrate to fat ratio insight and when it’s best to use an energy source to receive maximum results.