This is an interesting discovery, but I have a question about its uses for anyone that knows more about nutrition and/or biology than myself: If Bob has 50 grams of brown fat in his body and John has 0, how does Bob have an advantage over John? My perception is that Bob now has to eat 500 more calories per day than John just to survive. That doesn't seem like an advantage to me.

Am I missing something?

If we were still hunting for our food in the woods that wouldn't be an advantage and that may explain why in the cause of evolution, getting rid of brown fat with growing age, was a fitness criteria. In our "developed world" however, there is such a large availability of calories, that some people get more than enough. For those, being able to burn more, would be an advantage. Unless they are planning to go on a polar expedition anytime soon :)

I agree with your general sentiment though. Whether you could burn 500 calories more or eat 500 calories less isn't much of a difference. However, a drug that makes you burn 500 more calories and allows you to enjoy more eating is probably something that you can sell to a lot of people. Telling them to get their act together and eat right isn't that easily translated into profit.

I never thought about why people want to lose weight; I just assumed it was so that they can be healthy, but I suppose it could be entirely superficial for a sizeable crowd. Obviously, the health benefits of something like this would be minimal, but it would be great if someone just wanted to eat more junk food and not put on extra weight.

The health benefits to losing weight could be incredible. For example, the risk of a heart attack would drop and there would be less stress on the knees and ankles.

I imagine that it's useful as part of your thermoregulation if your climate is cold.

Cold muscles don't work as well, so your reaction time from "sleep to fight" would be improved I guess.

As calories have become more plentiful, the selection pressure against the waste has decreased, allowing something which is selected-for with babies to persist into adulthood.

That cleared it up for me; thanks for the information.

>A mere 50 grams of brown fat - well within the range of what some of us already have - could dissipate around 500 calories a day.

Amazing.