Nutrition theories abound. Each theory helps some people, so books are written extolling this diet and that approach. As a physician who specializes in this area, I have worked with over 35,000 clients. Some have followed different systems before I worked with them, and I always ask for their feedback. I also experimented with a number of the ideas, if not all of the ones described below. This is a report on my observations of what works and, when I can figure it out, why they work or do not work as well as claimed.