In 1996, a naturopathic physician named Peter J. D’Adamo published a book titled “Eat Right 4 Your Type.” The book’s premise is that our bodies respond to different foods based on the four major blood groups: A, B, AB or O. Each blood type processes some foods better than others, it claims, and people should eat the right foods – and avoid the wrong foods – to improve digestive health, increase general well-being and lose weight.
The book made the best seller lists, and lots of people decided to find out their blood type in the pursuit of weight loss. That’s not surprising. Those looking to lose weight will try almost anything, especially a diet proposed by a physician. There are countless specialty diets out there, each of them with adherents and skeptics. The blood type diet is no different.
It’s also no different from many other diets, in that it may help you lose weight in the short term. But like those other diets, it’s not for the reasons it claims.
How It (Supposedly) Works
The book says that not only food, but also your choice of condiments, spices, supplements, relaxation techniques and exercise should depend on your blood type. For instance, those who have type O blood are better served by high-intensity aerobic exercise and advised to take supplements for their digestive tracts, while those with type A blood should stick with low-intensity workouts and take up meditation, according to an article on the Harvard Health Blog.
On the food front, the article summarizes the “Eat Right 4 Your Type” guidelines this way:
- Type A: Focus on fruit, vegetables, tofu, seafood, turkey and whole grains. Avoid meat. To lose weight, choose seafood, vegetables, pineapple, olive oil and soy, and avoid dairy, wheat, corn and kidney beans.
- Type B: Include meat, fruit, dairy, seafood and grains. To lose weight, choose green vegetables, eggs, liver and licorice tea, and limit chicken, corn, peanuts and wheat.
- Type AB: Go with dairy, tofu, lamb, fish, grains, fruit and vegetables. For weight loss, choose tofu, seafood, green vegetables and kelp, and avoid chicken, corn, buckwheat and kidney beans.
- Type O: Choose high-protein foods, and eat lots of meat, vegetables, fish and fruit. Limit grains, beans and legumes. For weight loss, prefer seafood, kelp, red meat, broccoli, spinach and olive oil over wheat, corn and dairy products.
Does It Really Work?
The science says, emphatically, no. A 2013 analysis in the American Journal of Clinical Nutrition concludes: “No evidence currently exists to validate the purported health benefits of blood type diets.” To validate these claims, “studies must compare the health outcomes between participants adhering to a particular blood type diet (experimental group) and participants continuing a standard diet (control group) within a particular blood type population,” it says. No such studies existed then, and none exist now.
“I took another look, and there are no new studies to date that I could find that provide any substantiation for the correlation between blood type and food,” says Elizabeth DeRobertis, a registered dietitian and certified diabetes educator with Scarsdale Medical Group, an affiliate of White Plains Hospital in New York.
There have been studies that debunk the diet’s claims, however. Most recently, a study published Dec. 4, in the Journal of the Academy of Nutrition and Dietetics by the Physicians Committee for Responsible Medicine, a nonprofit group of 12,000 doctors, found no association between blood type and body weight, body fat, plasma lipid (blood fats) concentrations or glycemic (blood sugar) control.
“We found that blood type made no difference,” Dr. Neal Barnard, president of the Physicians Committee for Responsible Medicine and the study’s author, said in a release. “While the blood type diet says that a plant-based diet should be better for blood type A and less so for blood type O, it turned out to be beneficial for people of all blood types, and there was no evidence that meaty diets are good for anyone.”
The blood type diet may help someone to lose weight, DeRobertis says, “but not likely for the reason that it claims.” When someone follows an eating program like this one, they are cutting out foods and likely taking in less calories than they did before. “This would be the primary reason for the weight loss,” she says.
Another reason for weight loss might be that this plan does not include processed foods or foods that are high in calories, sugar or saturated fat. “So, for many people, this may be an improvement over their current style of eating,” DeRobertis says. “I have heard people say that they did lose weight on the blood type diet, but usually they realize it is because they reduced their calories by cutting out less healthy foods, and sometimes even full categories of foods that they ate in the past.”
But that benefit is at best only a short-term one. Any diet that recommends cutting out foods entirely, especially foods you like, is destined to fail. “It is likely a matter of time before they put that food back in. Rather than doing anything overly restrictive, it is better to have all foods in moderation,” DeRobertis says.
What’s the Harm?
“If someone has very poor eating habits, and this approach motivates them and speaks to them, they can certainly try it as a way to take a step in the direction of more thoughtful eating. There will likely be no harm or downfall to following this plan,” DeRobertis says. “The plan itself is not dangerous, as it basically steers people towards healthy food choices. It may unnecessarily restrict some healthy foods for people.” For example, if your blood type plan eliminates dairy, make sure you get enough calcium from nondairy sources. The only danger, she adds, is “feeling duped or misled when someone finds out that this approach is lacking credible evidence.”
“Honestly, it’s kind of sad,” says Wesley McWhorter, the director of culinary nutrition for the Nourish Program at the Center for Healthy Living at the University of Texas Health Science Center at Houston School of Public Health. “There is so much misinformation from people with a vested interest in making money selling a bad diet. That’s what this is.” Restricting objectively healthy foods just because of your blood type “doesn’t make any sense,” he says.