This breath-monitoring device might determine your metabolism, but it probably won’t help you lose weight

The Path Breath and Fat Band is a new set of devices that claim to help users lose weight by giving them a detailed analysis of their metabolism. But while the company makes claims that are backed by science, some experts doubt the devices’ actual effectiveness. The set, which just launched on Kickstarter, is comprised of a wearable bracelet and a breath-analyzing device. The package starts at $279.

Here’s how the two devices work in tandem: a user breathes into the breath device for five minutes while either walking or performing another activity. The device monitors oxygen and carbon dioxide levels to estimate the user’s 24-hour metabolism, or, more precisely, when they’re burning fat. This measurement is referred to as the respiratory exchange ratio, and essentially it means that during rest or moderate exercise, your breath demonstrates whether you’re burning more fat or carbohydrates. So taking that ratio into account, Path can say how much daily exercise each person needs to reach a weight-loss goal, or rather, to burn fat. This breath test should be done at least once a month to keep it accurate, Path says.

a literally named band

Meanwhile, the Fat Band is worn daily. It measures heart rate and syncs with a companion iOS or Android app to notify users when and for how long they should work out to burn fat. Path says it can cater exercise to individual ratios in an effort to optimize a workout.

I sent this Kickstarter to two scientists: Terence H. Risby, a doctor who specializes in breath research, and Andrew Coggan, an associate professor in the Department of Kinesiology at Indiana University-Purdue University Indianapolis. Both doctors agreed that while the science behind Path is legitimate — breath analysis for metabolism has existed for decades — it might not actually help a person lose weight. Ultimately, to lose weight, you need to consume less food than you burn off each day. So really, just eat less and work out more and you’ll lose weight.

Path Design

Risby told me that he believes most people’s metabolic rate is incredibly similar. “It’s just that you might need differing amounts of food depending on how much activity you do,” he said. So would calculating your metabolism help much? Probably not.

Coggan notes that people often mistakenly think a person can only lose fat by burning fat, as indicated by a certain heart rate or breathing zone. This, he says, is “not real.” Instead, again, it comes down to eating. “Exercise alone is insufficient to lose body weight.”

With that in mind, however, Coggan thinks the device could prompt a “novelty effect” in which people work out more because they have this new device telling them to exercise. That’s not so bad. “On the one hand, anything that encourages people to be cognizant of their health is a good thing in most cases,” he said. “At the same time, I don’t expect [the Path devices] to be a major breakthrough in the world.”

Path has already reached its Kickstarter goal.