A 2017 Study Linked 19-Degree Sleep to More Brown Fat
In a small 2017 study, volunteers gained brown fat and insulin sensitivity after a month at 19 degrees Celsius, then lost ground in warmer months.
Andrew Huberman · Essentials: Cold & Heat Exposure for Metabolic Health | Dr. Susanna SøbergSleeping in a 19-degree Celsius bedroom for a month was linked to more brown fat and better insulin sensitivity in a small 2017 study, even with pajamas and a duvet on.
In the Hansen and colleagues study, described by cold-exposure researcher Dr. Susanna Søberg, volunteers started with a baseline month sleeping at 24 degrees. They then spent a month at 19 degrees, followed by months at 24 and 27 degrees, and brown-fat activity and insulin sensitivity fell during the warmer months.
Brown fat may explain the shift. Its cells build more energy-making structures that burn glucose and fatty acids from the blood to make heat, which can lower circulating sugar and fat. White fat remains needed as energy storage.
A likely explanation is that cold on the face was enough to trigger the effect, since facial skin has many cold sensors. Søberg noted that even a hand in cold water can activate brown fat, and her own test with four minutes in 4-degree water raised skin temperature over brown fat near the collarbones.
Questions people ask
What is brown fat?
Brown fat is a heat-making type of fat, mostly near the neck and collarbones. Unlike white fat, which stores energy, brown fat burns sugar and fat to keep body temperature steady.
What does better insulin sensitivity mean?
It means the body needs less insulin to move sugar from the blood into cells. Higher insulin sensitivity is generally linked to healthier blood sugar control and lower diabetes risk.
Should I turn my bedroom down to 19 degrees?
The study suggests cooler sleep may affect metabolism, but it was small and short. People with heart problems, poor circulation, very young children, or older adults sensitive to cold should be cautious and talk with a doctor first.