Brown Adipose Tissue - Function in Infants

Function in Infants

In neonates (newborn infants), brown fat, which then makes up about 5% of the body mass and is located on the back, along the upper half of the spine and toward the shoulders, is of great importance to avoid lethal cold (hypothermia is a major death risk for premature neonates). Numerous factors make infants more susceptible to cold than adults:

• The higher ratio of body surface (proportional to heat loss) to body volume (proportional to heat production)
• The higher proportional surface area of the head
• The low amount of musculature and the inability or reluctance to shiver
• A lack of thermal insulation, e.g., subcutaneous fat and fine body hair (especially in prematurely born children)
• The inability to move away from cold areas, air currents or heat-draining materials
• The inability to use additional ways of keeping warm (e.g., drying their skin, putting on clothing, moving into warmer areas, or performing physical exercise)
• The nervous system is not fully developed and does not respond quickly and/or properly to cold (e.g., by contracting blood vessels in and just below the skin; vasoconstriction).

Heat production in brown fat provides a baby with an alternative means of heat regulation.