The only downside is that when I was obese I was never cold and could walk around in shorts and t-shirt all year round. Therefore, my brown fats never needed to wake up or conversely they were firing constantly helping to reduce blood glucose, who knows! Nowadays I feel the cold and have had to buy jumpers.
If you wake the brown cells up artificially then are we not likely to have obese people collapsing due to overheating! An interesting article but a lot more investigation needed with pre-state and consequencies