Brown fat or Brownies?Brown fat, which, unlike white fat burns energy instead of storing it, was always previously thought to be found and active only in infants. In 2009 it was reported for the first time that brown fat is metabolically active in adult humans too, perhaps between 3 and 7.5% of adults, with higher rates among women.Researchers reviewed scans that had been conducted on 172 children ages 5 to 21. Active brown fat was detected in 44% of the children, with the rate about the same for girls and boys. Children aged 13 to 15 had the highest percentage of detectable brown fat and the highest brown fat activity. But in addition, body ...