The claims are undoubtedly grandiose. Lumen claims that by measuring the amount of carbon dioxide in your breath, its analyzer can monitor your metabolism. As a result, it can tell you whether you're burning carbs or fat so you can adjust your food intake accordingly. Use the device for long enough, and it will even recommend recipes to match your personal situation.

The device itself is about the size of a regular asthma inhaler. Users blow into the mouthpiece. The results appear in the accompanying smartphone app. The app then uses the data to suggest dietary goals for the upcoming day. Goals include advice such as "Eat more pasta", "Get some extra sleep", or "Skip your workout today".

Exercise fanatics will also find Lumen very useful. Testing your breath before a workout will tell you whether you have enough fuel in your system to get you through your session. At the end of your workout, you can use the device for a second time to the effects of your routine.

Lumen is only available in black.

According to the company, the device has been heavily tested by users. Scientists, however, have their doubts. There is yet to be any serious academic research that backs Lumen's product. In the company's defense, it has made all its research public and readily invites feedback.