Boosting a lipid fuel makes mice less sensitive to the cold

Humans, like other animals, become more sensitive to cold with age. Now, scientists report that delivering a single dose of a nutritional supplement called L-carnitine to older mice restores a youthful ability to adapt to the cold. After treatment, they tolerate chilly conditions that would ordinarily trigger hypothermia. The supplement works by boosting levels of a newly discovered fuel source for brown fat, or "good fat".