Sometimes we can become intrigued by an idea that sounds good in theory, such as the claim that foods will react differently depending on your blood type, and that, to lose weight optimally, you therefore should adapt your diet depending on what blood type you have. These claims need to be backed up by studies showing that a population adapting their diets to blood type lose weight faster than a population that doesn’t do this.
Test tube studies displaying how different blood foods grow in various blood cultures may give some support, but is far from enough. Claims from thin air that foods react differently to different blood types are definitely not worth listening to.
In the case of blood type diets, no such evidence exists! Based on what we know today, the recommended diet advocates a diet high in whole foods, protein and vegetables; something that pretty much EVERYONE benefits from. The one study that exists found a positive effect of this diet on risk factors for heart disease, but these benefits were seen in all blood types, meaning that the diet’s results have nothing to do with if you are blood type A, B, AB or O.
Cusack L. Blood type diets lack supporting evidence: a systematic review. Am J Clin Nutr. 2013 Jul;98(1):99-104.
Wang, Jingzhou et al. ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors. Ed. Nick Ashton. PLoS ONE 9.1 (2014): e84749. PMC. Web. 12 Feb. 2017.