Q: Whatever happened to the blood type diet? Is there any evidence it works?
A: It’s still around—and still lacks scientific credibility. Popularized by the naturopath Peter D’Adamo in his 1996 book Eat Right 4 Your Type, the diet is based on the notion that people process food differently depending on their primary blood type (O, A, B or AB), which supposedly evolved at different points in human history. Eating the foods that your early ancestors ate at the time when that blood type arose will help you lose weight and lower your risk for chronic diseases, he says. In contrast, eating a diet not in line with your ancestral blood group causes adverse reactions between lectins (sugar-binding proteins) in food and your blood-type antigens, along with other problems.
If you have blood type O (which D’Adamo says dates back 30,000 years), you are a “hunter” who should eat a lot of meat (and avoid grains), but if you have blood type A (dating back 20,000 years), you are an “agrarian” who should eat a mostly vegetarian diet. B types (from 10,000 years ago) are “nomads” who thrive on a varied diet that includes dairy, while AB types (from just 1,000 years ago) are “enigmas” who should eat a combination of A and B diets.
D’Adamo’s approach itself has evolved over the years, and he now also touts diets based on six “GenoTypes,” which you can determine based on your fingerprints and other body measures.
But the program’s farfetched premises remain utterly unproven. A 2013 systematic review published in the American Journal of Clinical Nutrition concluded that though there is a possible link between certain blood types and increased vulnerability to particular diseases, “there is currently no evidence that an adherence to blood type diets will provide health benefits.”
Moreover, a large study in PLOS ONE in January was the first to provide evidence that actually debunks the claims. Though the diets were linked with some favorable cardio-metabolic risk factors, the associations had nothing to do with one’s blood type.
So why does the program seem to help some people lose weight? Like all fad diets, it may work in the short term simply because it instructs you to eliminate groups of foods from your diet and thus tricks you into consuming fewer calories.