Levl says it can tell you how much fat your body is burning just by analyzing your breath. The device comes in two parts: users breathe into a grey pod and then insert it into a white docking station. A few seconds later, details about your fat burning levels appear on the outside of the dock. A companion app also goes in depth about what those levels mean in terms of calories burned and pounds lost. It's technology that's based off a long proven medical technique. However, the research validating the product itself still seems somewhat thin.

Levl is supposed to work by measuring the amount of acetone in a person's breath — an indicator of how much fat is being burned in the body. Whenever we consume lots of carbohydrates, those get broken down into glucose and used for energy. But if you eat less carbs, the body runs out of its primary energy source. So it starts burning chemicals in fats instead — a process known as ketosis. This breakdown ultimately creates acetone, which is expelled in the breath. More acetone in the breath is supposed to correlate with higher fat burn.

Levl is looking for acetone in your breath

Recent diet fads have seen many people trying to induce ketosis to lose weight. The concept is easy: eat way less carbs, burn more fat. Research has shown that these ketogenic diets may be effective weight loss methods for those suffering from obesity. However, the idea comes with some controversy, and it's not clear if the diet aids with weight loss long-term.

Promoting ketogenic diets isn't quite the aim of Levl. Instead it's interested in letting you know just how much your body has turned to fat as an energy source over glucose. A spokesperson for Levl said the goal is to provide a snapshot for users about their diet trends to help them make healthier choices. So if you see you're burning less fat at the beginning of the week, for example, you might want to try eating less carbs over the weekend.

Using breath acetone as a marker for fat burn is definitely a proven method, backed with lots of research. Levl's tech doesn't seem to have many peer-reviewed studies validating its claims yet, though. On its website, the company lists a study published in the journal Obesity. That research is just a review of the scientific approach Levl is theoretically supposed to use; it doesn't actually show if the product does what it says it does.