I recently found Dr John McDougal on YouTube who has the solution to obesity based on history, current societies, and science. There seem to be two rules: 1) Base your diet around starchy vegetables (potato, wheat, oats, rice, corn, etc). 2) avoid fats, especially refined fats, and protein. 3) salt and sugar are not health foods, but are allowed to help you stick with rules 1 and 2. People, and societies, that eat like this are thin and healthy.