When children and adults are cold, they shiver as a way to create heat. Shivering causes muscle contraction, which in turn, creates warmth.
But did you know that babies don’t shiver?
The reason that babies don’t shiver is that they have a special type of fat (adipose) tissue, called “brown fat”. Brown fat burns more calories than adult fat (which is whitish yellow in color) and releases more heat. Babies have brown fat around their necks, chests, back and butt, and the brown fat acts like a warm coat to keep them warm.
Of course the brown fat is not enough to keep babies warm in the cold, and they still need to be bundled up.
A recent study with PET scans found that some adults still have brown fat. Interestingly, these adults tended to be thinner than people without brown fat, probably because the brown fat is burning more calories.