• Thermostat settings during the night can influence the composition of different types of fat in the body.
  • Research in both mice and people indicates that a colder sleeping temperature likely promotes the development of brown fat, which can bring potential health benefits.
  • While much more research is needed, studies suggest that a temperature around 66 degrees Fahrenheit (19 degrees Celsius) brings metabolic benefits without being too frigid for most people.

How our bodies function while sleeping depends on many different variables, and increasingly, research is finding that the temperature of the bedroom is one of those variables. A room with a cooler sleeping temperature may encourage beneficial changes when it comes to body composition and metabolism. These changes come predominantly from brown fat.

What Is Brown Fat?

Brown fat is a type of fat that exists in small quantities in the body and is sometimes known as a “good fat.”

When we usually talk about fat in the body, what we are actually talking about is white fat. Accumulation of white fat in the body can contribute to numerous health problems affecting a range of different bodily organs. But there is another type of fat — brown fat — that is different because it is metabolically active.

White fat is much more prevalent in the body. In fact, it is so much more common that for years, scientists weren’t sure that brown fat — which is found in rodents — was present in humans at all. The total amount of brown fat in the body is usually a few teaspoons at most, but even this amount of brown fat may be productive for the body.

In mice, brown fat has been found to burn calories to help stabilize the body’s core temperature, and the way that it does that is by removing sugar from the bloodstream. There is much that is still unknown about how brown fat functions in humans, but early indications are that it promotes metabolic health.

How Does Sleeping Temperature Affect Brown Fat?

A very small initial study in people, conducted by the National Institutes of Health (NIH), found that people who slept in cold rooms had more brown fat than when they slept in warmer rooms. They also showed improvement in metabolic indicators as, for example, the study participants had improved insulin sensitivity when they slept in cold rooms.

What Is the Best Temperature for Sleep?

A great deal more research is needed before anyone can declare that the optimal sleeping temperature has been identified. That said, the research conducted at NIH found health benefits for people sleeping in a room kept at 66 degrees Fahrenheit. The study subjects wore light clothing (hospital scrubs) and used only light sheets. In the study, the health benefits were detectable after only 4 weeks of sleeping in a room of this temperature; however, these benefits evaporated after subsequently sleeping for 4 weeks in hotter temperatures (75 degrees and 81 degrees).

What Other Factors Should Be Considered?

In the study, the sleepers did not use heavy bedding in order to keep warm. It may be that the benefits of a lower thermostat setting will not be accrued if you layer on more clothing, blankets, or quilts.

In addition, a cold room may affect some people’s ability to fall asleep in the first place. If trying out a low temperature disrupts your overall sleep, you may not accrue the same health benefits as were found in the NIH study. In other words, it may not be worth it to turn down the thermostat if that just keeps you up at night.

Lastly, depending on the climate where you live, keeping your bedroom at a low temperature may be costly. For people based in very warm regions, be prepared for an increase in your electricity bill if you are setting the thermostat to 66 for the entire night.

Want to Read More?

An overview of the initial study mentioned above is available directly from the NIH, and for those who really like to dig into the science, you can read a detailed article about brown fat from the journal Diabetes. For more information about metabolism and metabolic disorders, you can review this portal for information from MedlinePlus, a service of the National Library of Medicine.