Think you only burn calories when you’re working out, walking, or cooking dinner? Think again.

You can actually torch extra calories while you sleep — and the secret might be as simple as turning down your thermostat.

Yes, sleeping in a cooler room doesn’t just help you rest better — it can also boost your metabolism and increase calorie burn — all while you’re doing absolutely nothing.

The Science Behind Sleeping Cool
A fascinating study conducted by the National Institutes of Health (NIH) found that men who slept in a room cooled to 19°C (66°F) for a month experienced a 42% increase in brown fat — the “good” fat that burns energy to generate heat.

Even more impressive?
They burned nearly 200 extra calories per day — just by sleeping in a cooler environment.

But what is brown fat , and why does it matter?

Brown Fat vs. White Fat: The Metabolic Game-Changer
Most of the fat in your body is white fat — the kind that stores energy and accumulates around your waist, hips, and thighs.

But brown fat is different.
It’s packed with mitochondria (the powerhouses of cells) and burns calories to produce heat , especially in cold conditions. Think of it as your body’s natural furnace.

Babies have a lot of brown fat to stay warm.
Adults retain small amounts — usually around the neck and shoulders.
When activated (like by cold exposure), brown fat burns stored fat and glucose to keep you warm — effectively turning your body into a calorie-burning machine.
Sleeping in a cool room activates this fat , helping you burn more calories — even at rest.

Why Cooler Temperatures Help You Sleep Better
Beyond calorie burn, a cooler room improves sleep quality — and better sleep supports a healthier metabolism.

Here’s how: