So, why has Peter’s book become one of the best selling diet books in the past two decades? Because it works – but only for about 44-62% of the people who adopt it. Remember that for blood type O, Peter advocates a high meat, low carbohydrate "hunter" diet; with virtually no wheat, few grains or legumes and limited dairy products. If we look at the frequencies of the four major blood types for the entire world population, blood type O is by far the most frequently occurring version. It is found in 62% of all the world’s people, followed by A (21%), B (16%) and AB (1-3%)6. In the United States, the four blood type frequencies are O (44%), A (42%), B (10%) and AB (4%)7. So you can see that Peter has essentially advocated a diet similar to the Paleo Diet for between 44 and 62% of his readers. Quite simply, Peter’s diet works for about 44 to 62% of the people who adopt it – not because of their blood type, but because it emulates the same diet that natural selection has designed for us all.