Not all fat is white and wobbly. Some appears brown, because it’s full of tiny cellular factories called mitochondria, which generate heat and chemical energy. This brown fat is leaner and healthier than white fat, as it uses up fat molecules as well as storing them. Small rodents have it in abundance and use it to produce heat when they wake up from hibernation. Only tiny amounts of brown fat exist in adult humans, but newborn babies have a patch around and between their shoulders, as shown on this reconstruction (brown fat coloured green). MRI scans, biopsies and biomedical tests have been used to map its position. Brown fat helps keep babies warm, but most of it disappears as they grow up. Scientists don’t yet know why or how this happens. A better understanding could uncover new ways to fight obesity.
Written by Emma Stoye
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