Definition
In one paragraph.
Brown fat — the tissue that burns to make heat.
In practice
How the method uses it.
Brown adipose tissue is activated by cold and burns calories to warm the blood. Cold exposure recruits more of it. Seals live on it; humans have more than they thought.
Step by step
The protocol.
Step one
Regular cold exposure.
Step two
Shivering is the signal; adaptation is the goal.
Step three
Patience over weeks.
Safety, plainlyNever practice breathing exercises in or near water.
Evidence
What the science says.
Vosselman 2014 (PLOS ONE twin study) suggested brown fat is not the primary mechanism of Wim's heat; brown fat research otherwise supports cold recruitment.
Avoid
Common mistakes.
Believing brown fat explains everything.
Go deeper
Related.
Never in or near waterWim Hof Method breathing, when done intensely for multiple rounds, can in rare cases lead to loss of consciousness. Always practice seated or lying down, in a neutral space such as a living room — never in water, in the shower, while driving, or operating machinery. Read the safety doctrine.