The consensus among dietitians, physicians, and scientists is that these diets are unsupported by scientific evidence.
[3][4][5][6][7] In what was apparently the first study testing whether there was any benefit to eating the "right" diet according to one's blood type, a study published in 2014 compared "biomarkers" such as body mass index, blood pressure, and serum cholesterol and insulin among young people, and assessed their diets over a period of a month.
[5] That hypothesis is, in turn, based on an assumption that each blood type represents a different evolutionary heritage.
D'Adamo, a naturopath, is the most prominent proponent of blood type diets.
[2] Luiz C. de Mattos and Haroldo W. Moreira point out that assertions made by proponents of blood type diets that the O blood type was the first human blood type requires that the O gene have evolved before the A and B genes in the ABO locus;[9] phylogenetic networks of human and non-human ABO alleles show that the A gene was the first to evolve.