A nutritionist proposes a dietary plan to his client, based on his personal molecular profile, to manage his blood glucose. This dietary plan encourages the consumption of pizza whereas potatoes are discouraged. On the other hand, the counselor encourages the consumption of potatoes to another client to regulate the same risk factor. Is that science or fiction? This case illustrates a real situation published recently (1). As many as 137 parameters were measured in a first cohort of subjects participating in this study. Using this dataset the researchers developed an algorithm, which predicted the glycemic response of a second cohort of subjects to the ingest ion of specific foods. What is the scientific background behind these developments?