For the Harvard study, which appeared online in Proceedings of the National Academy of Sciences, researchers gave mice either raw or cooked meat and sweet potatoes and tracked their weight. They found that in both cases the cooked food packed more of a caloric punch. Mice that ate cubed, raw meat actually lost weight because so much energy was required for the animals to metabolize the protein. Pounded raw meat, which was easier to digest, provided a bit more energy, but not close to the levels provided by the cooked meat.
According to NPR, these results could give us insight into how humans evolved. Humans, like mice, require a lot of energy to digest complex, raw proteins and starches — that means less energy directed to help the brain. When humans learned how to cook, not only did they make food more appealing in terms of taste, they also helped make food more easily digestible. Less energy spent digesting means more energy spent developing a large and complex brain — and hunting down the next meal. For ancient humans, learning how to cook wasn't just a hobby; it was the key to evolution.
Unfortunately, modern humans don't spend the majority of their time stalking wild beasts or gathering berries. We also consume a lot more cooked meat than our ancient ancestors. The extra energy from the cooked meat is settling into our hips and stomachs rather than being put to good use. According to NPR, research has found that people gain more weight when a large part of their diet is meat (presumably cooked). In 2012, the government will require that meat packages contain nutrition labels, but those labels will not correctly reflect the increase in energy that occurs when meats are cooked.
Does this mean we should all start eating only steak tartar or beef sashimi? That's not quite what scientists are suggesting. Rather, carnivorously-inclined humans should just keep their meaty intake in mind and maybe get out for a good, old-fashioned run in the woods every now and then.