Everyone knows that getting a good night’s sleep can help you lose weight, but exactly how your sleep affects your metabolism is only now coming to light. One recent study found that people who experienced the recommended amount of sleep saw a 17.2 percent decrease in body fat, versus only 7.1 percent in those who didn’t. The metabolic threshold of those who slept well also improved by 29.8 percent, providing clear evidence that sleep helps you get a much better workout and, consequently, lose weight.
We also know that flipping through your phone or watching Netflix before bed disrupts your sleep cycle (not to mention, your sex life), and if there’s one daily habit you should implement right now, it’s putting all electronics away at least an hour before bed. Now, a new study by the American Academy of Sleep Medicine has linked the impact of light exposure at night on your metabolism, and there’s at least one clear takeaway: If you’re looking to lose weight, you want your sleep quarters as dark as humanly possible.
Researchers placed 20 healthy adults aged 18 to 40 into two different groups for two nights at the Northwestern University Feinberg School of Medicine. Both groups had the opportunity to get the recommended eight hours of sleep, but the difference was that one room was completely dark, whereas the other had a light exposure of 100 lux, the amount you usually find in office staircases. One group slept in the dark room on the first night and in the room with a little overhead light on the second, whereas the other group slept in the room that was totally dark on both nights.
The researchers drew hourly blood samples for melatonin and measured brain waves, the blood oxygen levels, and heart rate and breathing. They also conducted oral glucose tolerance tests on them the following morning.
What they found was that not only did participants sleep much better in the room with overall darkness, they had much lower levels of insulin. This is a major finding, because insulin is the hormonal signal to the body to increase weight. The higher your insulin levels are, the more weight you gain, regardless of how much you eat or exercise.
“Our preliminary findings show that a single night of light exposure during sleep acutely impacts measures of insulin resistance,” lead author Ivy Cheung Mason said in a statement. “Light exposure overnight during sleep has been shown to disrupt sleep, but these data indicate that it may also have the potential to influence metabolism.”
So what does this mean for you? Firstly, it shows that you really can gain weight just by not getting enough sleep. But, perhaps more importantly, this highly clinical study also indicates the importance of sleeping in total darkness and limiting your exposure to artificial light before bed. You should also make sure the room temperature is kept at 60 to 64 degrees, as that, along with darkness, signals to the body that it’s nighttime and it needs to release sleep hormones.
If you live in a city, where artificial light floods into your window from the street lights outside, you might also want to consider investing in some curtains or a sleep mask. And if you really want to take your sleep up a notch, why not give Gwyneth Paltrow’s clean sleep routine a try?
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