What is brown fat?
Brown adipose tissue
Brown fat is a special type of body fat packed with mitochondria that burns energy to produce heat instead of storing it.
Regular white fat is a storage warehouse. Brown fat is a furnace. When you get cold, your body lights the furnace to keep you warm, burning fuel in the process.
Why it matters for aging
Babies have lots of brown fat to stay warm. Adults have less, mostly around the neck, collarbones and spine. Its brown color comes from its many iron-rich mitochondria.
In a study where adults spent six hours a day in a cool room for ten days, their brown fat became more active and their bodies made more heat without shivering. Because brown fat burns sugar and fat for heat, researchers are studying it for metabolic health, but the effects in adults are modest.
A common myth
Activating brown fat with cold showers is an easy way to burn lots of fat.
Cold does activate brown fat, and regular cold exposure increases its activity. But adults have relatively small amounts, and the extra calories burned are modest. It's a nice bonus for metabolism, not a weight-loss shortcut.
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Updated Nov 9, 2026 · All terms