Davis W. Freeman states in "Blood Type Diet Debunker: Does it Really Work?" up at CBS News [2010-10-06]:
"can eating according to your blood type help you lose weight? Fans of the so-called 'blood type diet' say it can [...] but mainstream health experts disagree. The diet was first popularized more than a decade ago by naturopathic physician Peter D'Adamo in his book 'Eat Right 4 Your Type' [...] according to D'Adamo, people evolved to eat according to their blood type [...] 'there's no sound scientific evidence that the so-called blood type diet is any more effective or any more beneficial for weight loss than is any other diet,' Katherine Zeratsky, R.D., says on the Mayo Clinic website [...] in other words, if you're trying to shed a few pounds, adopting the blood type diet might be a bloody waste of time."
Note: there's a lot that can be placed, regarding naturopathy, under the column "no sound scientific evidence", including the 'essentially naturopathic'.