You probably know that exposure to blue light from smartphones -- like turning off your bedroom lights and staring at your phone for 15 or 20 minutes -- makes it harder to fall asleep, and sleep deeply.

And you probably know that not getting enough quality sleep means you might be one the 50 million to 70 million Americans who suffer from chronic sleep disorders that decrease daily functioning by affecting decision-making and reasoning.

You might know that one study found not getting enough sleep carries a greater mortality risk than smoking, high blood pressure, and heart disease (the trifecta of longevity-killers.)

You might even know that research shows chronic sleep problems may be linked to Alzheimer's.

But what you probably don't know is is that your smartphone could also make you fat. 

Research presented at this year's Society for the Study of Ingestive Behavior Conference (sounds like a rip-roaring good time) shows that one hour of blue light exposure at night caused mice's brains to crave sugar: Mice drank more sugar during nights when they were exposed to blue light than during nights without.

To make things worse, their glucose tolerance was lowered, and lower glucose tolerance is a warning sign of Type-2 diabetes.

Why? Since retinal cells in your eyes are extremely sensitive to blue light, and since those cells transmit information directly to the parts of your brain responsible for appetite and cravings, blue light naturally increases your craving for sugar. (And, especially for men, can over time impair your ability to process that sugar, which can potentially lead to insulin resistance and elevated levels of blood sugar.)


So what can you do if you want to not only sleep better -- which will improve your mental and physical performance -- but also avoid increasing your craving for sugary calories?

One, don't take your smartphone, tablet, or computer to bed. When you turn off the lights... turn off all the lights.

And if going device cold-turkey seems like a bridge too far, put devices on blue light filter mode. Use Night Shift on iOS. Or try an app like f.lux to automatically adapt your display to the time of day.

After all, getting better sleep will improve your memory, your performance, your mood... and may also help you avoid gaining weight.

Reasons enough to make sure that when you go to bed, your smartphone does, too.