There is a very interesting book called "The Metabolic Typing Diet".

It states that there is not the perfect one diet which works for every person, but instead every person has to find out his/her metabolic type first and then he/she will be able to eat a diet working for him/her.

I took the test in the book and so did my parents and my boyfriend and we all had different results. It opened our eyes and we now understand why my father shudderes every time he sees me eat (I am clear protein type and he is a clear carbohydrate type).