What is the blood type diet? And is there any merit to the blood type diet?

Answers from Katherine Zeratsky, R.D., L.D.

There's no sound scientific evidence that the so-called blood type diet is any more effective or any more beneficial for weight loss than is any other diet.

The blood type diet, sometimes called the biotype diet, is based on the idea that your blood type — A, B, AB or O — should determine your diet, your exercise regimen and your medical choices. While there's some controversy even among proponents of the blood type diet, in general they say that food proteins called lectins are digested differently based on your blood type. If you eat food that's not compatible with your blood type, you may experience a host of health problems, including slow metabolism, allergies, asthma, cancer, heart disease and chronic fatigue.

On the other hand, proponents say, if you follow a diet that's tailored to your specific blood type, it will help you lose weight, improve chronic health conditions and help prevent certain diseases. For instance, a blood type diet may suggest that if you have type A blood, you should focus on a vegetarian diet with fresh, organic foods and that you should engage in calming exercises, such as yoga and tai chi, to help avoid the conditions you're more susceptible to, including cancer, heart disease and diabetes.

But there's no solid research evidence to support claims about a blood type diet. If you're trying to lose weight, focus on developing healthy eating and exercise habits that you can follow for a lifetime.

Aug. 12, 2010 See more Expert Answers