I read an article by Dr. Mehmet Oz in Parade Magazine that was published in the time frame of December 2009 / January 2010. He stated that to begin on the journey of health, one should eat four fruits and five vegetables every day, as well as a tree nut, a carbohydrate and a protein. A serving size is around the size of your fist.
When I eat like that, I do feel better, and I am not hungry.