Loren Cordain, the grandpappy of Paleo, gives a fascinating introduction to who we are and what we evolved to eat. Guess what? Eating more meat was one of the key changes that allowed a large, metabolically active brain to evolve.
In Sugar: The Bitter Truth, Dr. Lustig will teach you more than you ever knew about sugar, and what it does to your body. Heavy science part way through. Fascinating stuff. Now watch his lecture and cut your fructose consumption!
Pretty much the seminal lecture on the topic. Well worth watching for anyone contemplating a low carb/ketogenic diet or looking for a primer on the insulin hypothesis.