I think Blood type diet works only because it eliminates foods that contain lectins for type 0. (I have thought to post about lectins to this forum as I think they are really evil :) I stopped eating tomatoes and another foods that have high lectins content and my thyroid seems to be working better. I used to be very sensitive to cold. Whole summer when it was a bit colder day I was feeling cold.) I am definitely feeling better when not consuming lectins nor Mono-Sodium-Glutamat (Natrium Glutamat)
But I also think blood type diet does not matter much. We all have different needs. But Hv what you think about food combining ? I was a huge fan of food combining til I thought it was making me constipated. But actually I was feeling well when I was combining my food. It enhanced my digestion and I could eat 4000-5000 calories a day without gaining.