[Cletus.D.Yokel]

But it can only be toggled ‘on’ with strenuous exercise.

[crosdaddy]

Cold exposure toggles BAT, it’s why infants have a lot of it, they don’t possess the muscle mass to be able to shiver. Adults have very little BAT, and cold exposures activates it, as well as “Browns” some white adipose fat.

[itsahoot]

But it can only be toggled ‘on’ with strenuous exercise.

You forgot superior intellect.