One of the hottest diet fads nowadays is called the Paleo diet. It goes by the premise that humans are genetically predisposed to eating lots of meat, a few plants and fruits, and perhaps nuts. I guess this idea comes from a concept of Conan like cavemen hunting down and grilling mastodons as compared to a modern overweight guy munching on Cheetos while watching TV. It's an interesting idea....but complete bull.
First off, prehistoric humans actually ate....pretty much whatever they could find. They had no "diet" per se, just a day to day struggle to get enough food to survive. If that meant killing something, great. If it meant finding something that was already dead, even better and safer. The knowledge of any plant that didn't poison grandma was passed down through the generations. How did this truly paleolithic diet work out for the health and fitness of cavemen? They had a grand life expectancy of under 30 years...tops.
What we do have a genetic propensity for is in storing fat when it is available. Humans that were able to do this had a much greater chance of surviving frequent lean times. Cavemen most likely went a couple of days or longer without food on a regular basis. Modern humans have difficulty going a couple of hours without eating and, since most of us don't have to chase down our food or be chased by something that thinks of us as food, the storage of fat gets a bit out of hand. The greatly increased lifespan also makes the long-term effects of being fat a lot more obvious.
So...is the Paleo diet good? The premise is. Cutting out processed carbs is definitely good for your health. Raw (as in unprocessed and fresh) vegetables are absolutely good for you. Lean meat is, I believe, a healthy part of any diet too....to a point. Most people eat way more meat than necessary.
I still believe the best diet is common sense. Eat a variety of fresh foods. Avoid processed and canned items. Treat high fructose corn syrup like plutonium and stay away from it if at all possible. Use small portions. Get up and move around once in a while to burn all the fuel you put in your mouth every day.
Pretty simple. Not exciting or sexy and it doesn't sell books.