All that data is a treasure trove for insurance companies. Time to read the fine print.

Between cool new wearables and a phone full of fitness apps, our health routines have gone totally high tech. Most of the time that's a good thing-you can count your calories, measure how much you move, log your sleep cycle, track your period, and book barre classes all from your phone. All the data you're logging makes it easier to make informed health decisions. (Related: 8 Healthy Tech Innovations That Are Totally Worth Splurging On)

But you're probably not thinking about who else can use that data, which is a major problem according to a new study by the Future of Privacy Forum (FPF). After reviewing the massive amount of health and fitness apps on the marketplace, FPF found that a whole 30 percent of fitness-focused apps available don't have a privacy policy.

This is a big problem because it leaves us all operating in the dark, says Chris Dore, a partner at Edelson PC, a consumer privacy law firm. "When it comes to fitness apps, the data that's being collected starts to border on medical information," he says. "Especially when you're putting in information like weight and body mass index or connecting an app to a device that's taking your heart rate."

That information isn't just valuable for you, it's also valuable to insurance companies. "Data like what you eat and how much you weigh, collected over a period of time, is a treasure trove for health insurance companies looking to give you a price," Dore says. Definitely scary to think that forgetting to sync to a running app a few times a week could affect something as important as your health insurance coverage.

So how do you know which apps are safe to use? If you aren't asked to agree to the terms of service or don't see a privacy policy anywhere, that should raise a red flag, says Dore. Those annoying permission request pop-ups you get on your phone are actually pretty important since they're allowing the app to access your data. The bottom line: pay attention to the privacy policy on the apps you use. "No one ever does," says Dore. "But it's often a very insightful read with a big impact."