I thought a lot of the links to Richard Wrangham's research on the origins of cooking had already been widely shared on Hacker News. Here is a chronological list of a few stories on his research to show how this line of research has developed over the last decade.
http://img2.tapuz.co.il/forums/1_140989346.pdf
http://www.news.harvard.edu/gazette/2002/06.13/01-cooking.ht...
http://evolutionaryanthropology.duke.edu/uploads/assets/Wobb...
http://www.amazon.com/Catching-Fire-Cooking-Made-Human/dp/04...
http://www.artsci.wustl.edu/~anthro/articles/RW%20RC%20Ev%20...
I was very surprised when I saw the early dates (before the emergence of Homo sapiens as a species) for the earliest evidence of cooking. The current view is cooking actually enabled hominin evolution in the direction of smaller gut sizes and larger brain sizes, as is characteristic of Homo sapiens.
Nothing drains like being cold and having the ability to make fire would be a massive change.
Staying warm seems so unimportant compared to doubling or tripling your effective food supply.
As I admit though, I don't know if this is the same as the dietary movement we're talking about. I don't know any amount of science in either direction.
"... if a human nowadays were to try to eat purely raw vegetables, their digestive system wouldn't be able to extract enough calories per day to make up for the energy used to digest and stay alive."
Which is in the antecedent comment.
The human body is incredibly designed to not die if you don't eat anything. Basically, you have to not eat anything PLUS not have any useful fat left to burn PLUS not have any extra muscle to burn. Almost everyone in the Western world could go a month without eating and only suffer from lethargy and possibly a lack of non-fat-soluble vitamins. Eat nothing but take a multivitamin and you're theoretically good to go for months. There was the study published on one man who fasted for a full year and suffered no health detriment.
I tried to dodge that direct statement in my original post because I am not a health professional, I know nothing of the science behind the diet, and I'm not trying to make the argument that the diet would be a "good" way to lose weight.
http://hulu.com/watch/289122/fat-sick-and-nearly-dead (Fat, Sick & Nearly Dead)(2011)
http://blogs.discovermagazine.com/crux/2011/12/08/why-calori...
If you are warm and require less food that's less trips out to hunt and fewer chances of being injured or killed.
Maybe add onto that the cooking of food being digested better too.