Eating right for your blood type entails proper recording keeping because you need to know what foods your body has a negative reaction to. Those foods are basically allergens to your body and can cause not only inflammation but weight gain. When you keep a journal you can document what foods work and which ones do not. With the Blood Type Diet it is important to know exactly what foods work with your blood type--as well as with other factors. In fact The Blood Type Diet also relies on other factors that are individual to each person and these include what you eat (as documented) your age and the bacterial population of your body. Keeping a journal allows each person to note what works with his or her body and what does not.