To understand the idea behind the blood group diet, you should know first what are blood groups are and what is your blood type.
Although all the red blood cells have the same components, they differ in terms of molecules found on their surface, also known as antigens bodies. There are two main bodies antigens of red blood cells, called A and B. If you have type A blood, then you only have A antigens bodies of your red blood cells; Similarly, people with type B blood have B antigens only bodies. If you have type AB blood, then have both A and B antigens bodies, and if you have type O blood, it means you don’t have none of them.
If you have type O blood, your diet should primarily consist of protein sources such as meat and fish, and should be low intake of carbohydrates and dairy products.
For type A blood, avoid red meat, but eat a lot of fish and vegetables and eat smaller amounts of dairy products.
People with type B should eat a lot of meat and dairy products and lot of fruits and vegetables and also eat a moderate amount of fish.
The diet for people belonging to the AB blood type is essentially a combination of diet on type A and type B blood groups.
While it is true that food containing lectins, there is no evidence that lectins affect your blood cells or any other tissue in the body. There is no scientific evidence that diet towards your blood type has effects on weight loss and overall health. Talk to your doctor before you make any decision to apply diet based on your blood type.