Type Os thrive on intense physical exercise and animal protein. Unlike the other blood types, Type Os muscle tissue should be slightly on the acid side. Type Os can efficiently digest and metabolize meat because they tend to have high stomach-acid content. The success of the Type O Diet depends on the use of lean, chemical-free meats, poultry, and fish. Type Os don't find dairy products and grains quite as user friendly as do most of the other blood types.
The initial weight loss on the Type O Diet is by restricting consumption of grains, breads, legumes, and beans. The leading factor in weight gain for Type Os is the gluten found in wheat germ and whole wheat products, which interferes with insulin efficiency and slow down metabolic rate. Another factor that contribute to weight gain is certain beans and legumes (lentils and kidney beans) contain lectins that deposit in the muscle tissues making them less "charged" for physical activity. The third factor in Type O weight gain is that Type Os have a tendency to have low levels of thyroid hormone or unstable thyroid functions, which also cause metabolic problems. Therefore it is good to avoid food that inhibits thyroid hormone (cabbage, brussels sprouts, cauliflower, mustard green) but increase hormone production (kelp, seafood, iodized salt).
Several classes of vegetables can cause big problems for Type Os, such as the Brassica family (cabbage, cauliflower, etc.) can inhibit the thyroid function. Eat more vegetables that are high in vitamin K, which helps the clotting factor which is weak in Type Os. The nightshade vegetables can cause lectin deposit in the tissue surrounding the joints.
Because of the high acidity stomach, Type Os should eat fruits of alkaline nature such as berries and plums..
Type Os should severely restrict the use of dairy products. Their system is not designed for the proper metabolism. If you are a Type O of African ancestry, you should eliminate dairy foods and eggs altogether.