What Is It?

The “eat right for your type” diet, also known as the blood type diet, advises people to eat certain foods based on their blood type: A, B, AB, or O. This diet was developed by naturopathic doctor Peter D'Adamo in his book “Eat Right for Your Type: The Individualized Diet Solution to Staying Healthy, Living Longer & Achieving Your Ideal Weight.” D’Adamo claims that each blood type digests food proteins (called lectins) differently. He believes that eating the wrong foods containing the wrong lectins can cause negative effects on the body. These effects include slower metabolism, bloating, and even certain diseases, such as cancer.

D'Adamo’s theory relies on evolutionary theory associated with each blood type, with a corresponding diet and fitness plan.

Type O

D'Adamo says quick fight-or-flight responses are caused by having type O blood because this ancestral blood type is finely tuned to respond to the stresses of ancient times. According to the diet plan, people with this blood type will benefit from a high-protein diet of lean meats and fish, limited grains and breads, and intense exercise.

Type A

After agriculture reduced the need for hunter/gatherer lifestyles, this blood type developed in order to better use nutrients from carbohydrate-based foods, according to D’Adamo.

The type A diet plan emphasizes soy proteins, grains, and vegetables, and restricts red meat. It also suggests a lighter exercise regimen.

Type B

D'Adamo traces the history of this blood type back to nomadic Asian peoples. He describes people with this type as being more genetically suited to thrive in varied conditions. As a result, he says type B dieters can tolerate dairy products and can also enjoy meat and most produce. This plan restricts corn, wheat, lentils, tomatoes, and peanuts. It suggests moderate exercise.

Type AB

This blood type shares characteristics with types A and B. Type AB dieters are encouraged to avoid meats but can safely eat tofu, seafood, dairy, and most produce. This plan suggests a mix of calming and rigorous exercises for a balanced fitness routine.

The blood type diet promises that it understands you as a "biochemical individual." It claims that changing your diet to be based on foods that are determined to be beneficial for your blood type will lead to weight loss, increased energy, and lasting health. The promise of this diet is less about weight loss and more about improved health, mental clarity, and resistance to disease. The plan offers individualized eating plans for better health.

Pros and Cons

thumbs up Pros
  1. The blood type diet emphasizes that every person is different when it comes to dieting.
  2. A more active lifestyle is encouraged along with the diet plan, which is aimed at improved overall health.
  3. Some people have reported successful results.
thumbs down Cons
  1. There’s no independent scientific research that backs up the claim that dieting based on your blood type has any effect.
  2. It’s often not easy or practical to eliminate or restrict categories of food, and most nutritionists don’t recommend it.
  3. It could be difficult for groups to try this diet together.

This diet plan emphasizes that every person is different when it comes to dieting, which is a sound foundation. There is no caloric restriction on this diet. This means less chance of the hunger pangs normally associated with dieting, but it may not produce much actual weight loss. It does encourage a more active lifestyle of varying degrees of exercise (based on blood type). There also seem to be plenty of people who have reported having success on this diet plan. D'Adamo's website has lots of information and support forums for those who are interested in exploring his approach.

The blood type diet runs into problems with the lack of research available to back up D'Adamo's claims. The medical community doesn’t support the idea that blood type has many connections at all to health, let alone the benefit of specific diets for each blood type. One study found that D’Adamo’s diet plans did have some health benefits, but that these didn’t correspond to blood type. For example, anyone following the type A diet was more likely to have a lower BMI, smaller waist, and lower blood pressure, whether or not their blood was type A. In response, D’Adamo said that the researchers didn’t evaluate enough different foods to properly test the effects of the blood type diet.

Another factor to consider is that most nutrition experts don’t recommend limiting or restricting entire categories of foods. It’s also not very easy or practical to do for many dieters. The individualized nature of this diet also means it would be difficult for families or groups to try together. Different blood types would require different eating plans and exercise programs.

Healthline Says

The idea of being tied to our ancestors by tens of thousands of years of blood type evolution can sound very intriguing. It's easy to understand why people are drawn to this diet; it sounds really scientific. But there are plenty of smart people who question that science. D'Adamo has dedicated a section of his website to personally responding to several critics, pointing out apparent hidden motives for each critic, whether they are hawking a competing diet book of their own or just against alternative medicine altogether. There is also plenty of access to D'Adamo's own research on the site.

While a section on D'Adamo's site labeled "Independent Scientific Evidence" would go a long way to quiet critics and help his cause, we really care more about how practical and healthy the diet plan is. We agree with D'Adamo that dieting is an individualistic process. But if you are a die-hard carnivore who happens to be blood type A, it doesn't seem practical to think that you will stick with a diet that eliminates meat. On the other hand, if you were to cut back a little on meat, follow the recommended plan, and start to lose weight and feel better, there could be incentive to make long-term adjustments — science or no science.

Each person is unique, whether because of their blood type or, more importantly, their personal preferences. Nutritionists don't recommend cutting out entire groups of foods — that can lead to unbalanced nutrition and make it harder to stay on the diet for an extended period. Pay attention to the scientific claims for this diet, given the lack of independent research. But if you are intrigued, talk to your doctor or a dietitian to see if the blood type diet is safe for you. They can help you figure out a practical approach to trying it out. If you get the nod, give yourself a trial period to see if the plan is effective for you personally.