How Much Data Do You Need?
Credit: Photograph by Justin Steele

Skeptical but curious – that's how I felt strapping on my first activity tracker, a Misfit Shine. All of these devices, from the Fitbit Flex to the Jawbone UP24, promise to get a man fitter, better rested, and lighter around the middle. I'm not the leanest guy, and I don't sleep like I used to, so I wanted to believe. And I'd heard hype like this: One in 10 American adults owns a body monitor, and retail sales – $290 million in 2013 – are projected to double this year. But I also exercise plenty, and I couldn't see how a gadget counting my steps and hours in bed – what most of them do – would change my life. But then my little tracker started spitting out revealing data, and friends started sharing their own experiences. Soon, I was upgrading and narrowing in on the exact-right device, and becoming convinced that, to make those health promises a reality, it only takes a little knowledge about how these trackers work, what they're good for, and your own motivation.

Pick Your Goal for a Plan and Ideal Tracker:

1. You Want to Move More, and Lose a Few

2. You're a Data Junkie Who Wants to Dial Up His Fitness

3. You're a Wannabe Pro