Everything You Should Know Before Trying a Blood Type Diet for Weight Loss

By Macaela Mackenzie
Oct 3, 2019

Diets have historically taken a one-size-fits-all approach, but lately, nutrition advice has been all about getting personal. Thanks to the rising popularity of nutrigenomics—decoding your nutrition needs based on your genes—and a focus on creating healthy eating habits based on your lifestyle and preferences, diets no longer exist as they once did.

But not all personalized eating plans are getting the green light by the pros. One trendy diet causing controversy? The Blood Type Diet.

The idea behind the Blood Type Diet is simple: Just like your genes influence your weight and your body’s ability to process certain foods, so does—theoretically—your blood type.

But critics of the eating plan have been very outspoken about the lack of science supporting such a claim, even calling it a “crass fraud.” So, what exactly is the blood type diet—and is there any science to support it? Here’s everything you should know before trying it for weight loss.

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What is the Blood Type Diet, exactly?

Developed by Peter D’Adamo, a naturopathic physician and alternative medicine researcher, the diet targets your blood type—A, B, O, or AB—to make nutrition recommendations.

For instance, according to D’Adamo’s research claims, people with type A blood are more predisposed to heart disease, cancer, and diabetes. That’s why the type A eating plan is a vegetarian diet focused on foods that are “fresh, pure, and organic” to “supercharge your immune system.”

Meanwhile, those with type O blood thrive on animal proteins. The reasoning? “This blood type has a very well-developed ability to digest meals that contain both protein and fat,” his website states.

As for weight loss? Ditching foods that contain lectins—a type of protein that supposedly aggravates your immune system, spurs inflammation, and messes with your hormones—that interact with your specific blood type and replacing them with the ones recommended in your diet should boost your energy and help you shed pounds, according to D’Adamo’s site.

The Blood Type Diet Breakdown

- Type A: Eat vegetarian foods in their natural state (fresh and organic).

- Type B: Avoid chicken, corn, wheat, buckwheat, lentils, tomatoes, peanuts, and sesame seeds, and eat more green vegetables, eggs, low-fat dairy, and meats like lamb or venison.

- Type O: Load up on lean meat and healthy fats, but cut out grains, beans, and dairy.

- Type AB: Avoid caffeine, alcohol, and smoked or cured meats. Focus on foods like tofu, seafood, cultured dairy, and green vegetables for weight loss.

Can the Blood Type Diet help you lose weight? Or improve your health?
“The premise of the blood type diet is interesting from the perspective that it doesn’t recommend the exact same foods for everyone,” says Kris Sollid, RD, senior director of nutrition communications at the International Food Information Council Foundation.

Technically, the blood type diet can help you lose weight. “Any diet can lead to weight loss, but that’s related to the number of calories you eat, your age, and how active you are,” explains Sollid. More importantly, he says, weight loss does not solely determine whether or not your diet is actually good for you.

When you take a closer look at the research, scientific backing for the Blood Type Diet falls short. “There is no explanation to support a link between an individual’s blood type and their interactions with certain foods and weight,” says Nancy Rahnama, MD, a board-certified bariatric physician. One 2013 review published in the American Journal of Clinical Nutrition concluded that “no evidence currently exists to validate the purported health benefits of blood type diets.”

The next year, a new study explored whether the Blood Type Diet could improve health markers associated with heart disease and diabetes. After analyzing data from more than 1,400 patients, researchers discovered that sticking to certain blood type diet recommendations did have positive effects—like a lower BMI and blood pressure—but those were independent of a person’s blood type.

What’s more, a 2018 study published in the Journal of Nutrition found that the Blood Type Diet didn’t have any significant health impact on overweight adults.