Since then researchers have found that actually BAT is present in everyone (link) and that the amount is inversely proportional to BMI (i.e., the more BAT, the lower the BMI)
Another study (link) found that in normal weight men BAT was more active after fasting than after a meal and that being exposed to cold increased its activity even more.
Last, another study (link) of the so-called 'skinny gene' SIRT2 which is activated by calorie restriction, and by a short (24 hour) fast in white and brown adipose tissues is also activated by cold exposure in brown adipose tissue. Activation of SIRT2 promotes fat burning and inhibits fat cells (adipocytes) from multiplying.
So, this is more evidence that fasting can help fat burning and keep the fat cells in check. Also, when we are feeling cold during our fasts perhaps we should remind ourselves that we may get better fat burning from the cold!