What is it?

Developed by naturopathic physician Peter D'Adamo, the Eat Right for Your Type diet (a.k.a. the Blood Type Diet) advises people to eat certain foods based on their blood type: A, B, AB, or O. D'Adamo—who introduced the plan in his book Eat Right for Your Type: The Individualized Diet Solution to Staying Healthy, Living Longer & Achieving—claims that each blood type digests food proteins (called lectins) differently. Furthermore, he believes that eating the wrong foods containing the wrong lectins can cause ill effects on the body—including slower metabolism, bloating, and even certain diseases such as cancer. By avoiding the foods that are wrong for your blood type and eating foods that benefit your blood type, better health can be achieved. D'Adamo breaks each blood type down by the evolutionary theory behind each group that was posited in the 1950s.

Type O: This is the first blood type, the oldest of humanity. On his website, D'Adamo describes the type O ancestral prototype as "a canny, aggressive predator." 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 "the cultivation of grains and livestock changed everything" for humanity, this blood type developed based on "the need to fully utilize nutrients from carbohydrate sources." Thus, the type A diet plan emphasizes soy proteins, grains, and vegetables, restricts red meat, and suggests a lighter exercise regimen.

Type B: According to D'Adamo, this blood type possesses "potential for great malleability" and is associated with a flexible digestive system. Type B dieters can tolerate dairy products and can also enjoy meat and most produce. This plan restricts corn, wheat, lentils, tomatoes, and peanuts, while suggesting moderate exercise.

Type AB: As the name implies, 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 Promise

The Blood Type Diet promises that it understands you as a "biochemical individual" and that changing your diet to 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 & Cons

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

The Blood Type Diet runs into problems with the significant lack of independent research available to back up D'Adamo's claims. The medical community at large does not support an idea that blood type has many connections at all to health and especially to a specific diet for each blood type. Furthermore, limiting or restricting entire categories of foods is not recommended by most nutrition experts, nor is it easy to do for many dieters. And because of the individualized plans, this diet would be difficult for families or groups to try together because varying blood types would require different eating plans and exercise schedules.

Healthline Says

It all sounds very intriguing—being tied to our ancestors by tens of thousands of years of blood-type evolution. Browsing D'Adamo's website and reading through the basis and history behind the diet plan is fascinating. It's not hard to understand why people are drawn to this diet; it sounds really scientific. There have been plenty of smart people who question that science, and D'Adamo has even 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 the individual is a die-hard carnivore who happens to be blood type A, it doesn't seem practical to think that person will stick with a diet that eliminates meat. On the other hand, if that person were to cut back 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.

The point is that each person is different, whether it's blood type or, more importantly, personal preference. We don't recommend cutting out entire groups of foods. It leads to unbalanced nutrition and makes it harder to stay on the diet for an extended period. And although we aren't refuting it, we are wary of the scientific claims for this diet, given the lack of independent research. But if you are intrigued (understandably), talk to your doctor to see if the Blood Type Diet is safe for you and to 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.