Everyone's got that guy in the office—the one who does laps around the floor and sits on a stability ball all day “to lose belly weight”. Is he onto something? Or is it a waste of time?

Surprisingly, you can burn extra calories by sitting—or, to be more accurate, bouncing nervously—on a stability ball all day.

For example, a 185-lb man burns about 156 calories an hour doing normal desk work, Harvard Health Publications states. Adding a stability ball boosts that by 6%, to 165 calories per hour, or about 75 extra calories per eight-hour day—which adds up to 19,500 calories a year.

Plus, stabilizing yourself on the ball can help strengthen core muscles.

But here’s a heads-up: Studies show that sitting full-time on a stability ball can cause back strain and bad posture, and lessen circulation, so we advise using it sometimes, not all the time.