The only time you're supposed to take off your FIT is when you're going to get wet. You even wear it while you sleep. Is this because you're secretly sleep-exercising? Could it be you're a world-class athletic somnambulist? That's not likely, but it's clear that sleep plays an important part in weight loss.
A study published in the Annals of Internal Medicine found that dieters who cut back on sleep reduced their ability to lose fat by 55 percent [source: Science Daily]. Reduced sleep seems to have an effect on ghrelin production. Ghrelin is a hormone that plays a part in triggering the hunger response and reduces the amount of energy you expend. If you don't get enough sleep, your body will produce more ghrelin and you'll feel hungrier than normal.
The FIT tracks your sleep patterns the same way it tracks how far you've run or how many calories you burn as you pump iron. The sensors keep track of your movement, temperature and any changes in your skin's conductivity. Most people are pretty inactive once they go to sleep. When the FIT's data reflect this state, the software assumes that's when you've gone to sleep.
Throughout the night, you might move around in your sleep or even wake up a few times. The FIT captures all of these movements throughout the night and sends the data to your computer as you sync up. Based on this information, the software extrapolates how well you slept the night before. A steady signal could indicate you slept soundly for several hours, which is good news. But a data stream with a series of interruptions or spikes could show that you're not getting enough good sleep to help you in your goal.
What you do with this information is entirely up to you. You might need to look into changing your daily routine. You may have to adjust where you sleep. Keep in mind that you can be active and follow a sensible diet and still not lose the fat you want to get rid of if your sleeping patterns are bad.