The device measures the amount of a of carbon dioxide that you release in your breath. It determines your respiratory energy bibes, and it sinks with an ap on your phone. This doesn't really tell you whether or not you are priming the pump for weight loss,. But this does, i think, tell you a little bit about your metabolic flexibility... And there have been studies that have linked a more carbohydrate burning a with a predisposition for wait gane - which is correlational.