What is the primary function of brown adipose tissue (BAT) in newborns?

• A. To generate heat for distribution to other parts of the body.
• B. To store fat for energy.
• C. To regulate appetite and satiety.
• D. To produce insulin.

Answer: (A)

Brown adipose tissue in newborns is specialized for non-shivering heat production. It’s packed with mitochondria that contain thermogenin (uncoupling protein 1), which uncouples oxidative processes from ATP formation and releases energy as heat instead. This heat generation is crucial for newborns because they can’t rely on shivering to stay warm and they have a high surface area–to–body-mass ratio, making them prone to heat loss. So the primary role of brown fat is to warm the infant, distributing heat through the blood to keep the body’s temperature stable.

Storing fat for energy is the job of white adipose tissue, not brown fat. Regulating appetite and satiety involves hypothalamic signaling and hormones, not BAT. Producing insulin is a function of the pancreas, not brown fat.