LS Answers: Why can't babies shiver?

Have you got your shiver on?

With the onset of winter we are all feeling the cold at the moment in Leeds.  However, unlike adults, babies resort to burning fat rather than shivering.

When adults are cold, our bodies shiver to engage our muscles and produce more body heat.  However, babies do not have this ability to shiver and therefore warm their bodies through fat burning.   ‘Non-shivering thermogenesis’ is an adaptive mechanism, critical for the regulation of neonate’s temperature.  Babies increase their metabolic rate to produce heat, this is known as ‘thermogenesis’. They do this primarily through the breakdown of ‘brown adipose tissue’, or ‘brown fat’.

Brown fat, known for its colour, is a particular tissue type found in young babies.  It makes up 6% of the babies’ body weight and 40% of the body’s fat stores. This fat is filled with mitochondria, and when the body is fuelled with food the mitochondria aids the transformation of sugar into energy in the form of heat. Human infants are not the only organisms that possess brown fat, hibernating animals also have stores of brown fat to keep them from starving during the months they spend in hibernation.

During times of stress babies release hormones which are associated with the cold weather.  The break down of brown fat is then induced by the release of these thyroid hormones, ultimately producing heat for the baby.  Babies continue to use this method of heat production until they are able to adopt the ability to shiver like adults.

Despite keeping them warm, this method of thermoregulation is believed compromise babies’ calorie intake which is vital for the babies’ growth.

Brown fat was previously believed to only present in newborns, but scientists now believe that this fat tissue does not disappear with age. Therefore, it may seem that this burning of fat could be the new diet solution for adults.

Judy Paxman

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