Whether you like to bundle up with several layers of blankets or sleep on a bare mattress exposed to the elements, there’s no one right way to sleep. But if you’re trying to maintain a healthy weight, there might be: research shows that sleeping in a cold room could help boost your metabolism and make you burn more calories, even during the day.
When you were a baby, you had two types of fat. White fat is what you usually imagine when you think about fat: it stores calories. That’s pretty much all it does. Brown fat, conversely, is what you’d call metabolically active; it burns calories to generate heat. Babies haven’t yet developed the ability to shiver, so they need another way to stay warm — brown fat to the rescue. Once you got older and found other ways to maintain your body temperature, you lost most of your brown fat. Another sad truth about being human.
But a 2014 study published in the journal Diabetes suggested that you might be able to boost your body’s levels of brown fat by sleeping in a chilly environment. The researchers recruited five healthy male volunteers to sleep in climate-controlled rooms at the National Institutes of Health for four months (hospital scrubs and light sheets were provided — what luxury!). The researchers kept the men’s calorie intake controlled by providing all of their meals. For the first month, the men slept with the thermostat set to a neutral 75 degrees Fahrenheit (24 degrees Celsius). The next month, it was set to a chilly 66 degrees F (19 degrees C), then was reset to neutral for a month. They spent a final month sleeping in a toasty 81 degrees F (27 degrees C).
The cold temperatures had a big effect on the men’s bodies. After a month sleeping in the cold, the men had almost doubled their stores of brown fat, which helped improve their insulin sensitivity — a measure that’s affected by shifts in blood sugar, and is generally used as a sign of metabolic health. They even burned more calories during the day. But as quickly as the improvements came about, they were easily undone: the month of sleeping in warm temperatures actually reduced their brown fat to pre-experiment levels. Even still, that’s good news. To supercharge your metabolism, it may take just a month of chilly slumber. Brr and Zzz?
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