If you’ve been struggling with weight loss or lack of energy despite keeping a healthy diet, you might be interested in the Blood Type Diet. It’s a diet created by naturopathic doctor Dr. Peter J. D’Adamo, who posits that certain blood types may be more or less susceptible to certain illnesses and diseases, and that certain foods react differently with each blood type. In D’Adamo’s book Eat Right For Your Blood Type, he explains which foods to eat and which to avoid based on all four of the blood types: O, A, B, and AB.

D’Adamo’s hypothesis is formulated around the idea that each blood type corresponds with a different evolutionary period, with type O relating to the oldest hunter-gatherer era, type A with agrarian societies, type B with nomadic tribes, and type AB with more modern times. Following this theory, each blood type will react best to foods that resemble what would have been eaten during their respective evolutionary period. D’Adamo claims that once you’ve started to adjust to your appropriate diet you should see results such as weight loss, increased energy and increased immunity to disease.

So, here is what you should be eating according to your blood type:

Type O – Consists of a high-protein diet, which includes a lot of lean meat, poultry, and fish—just like what the hunters would’ve been eating. You should also stick to vegetables, but take it easy on grains, beans, and dairy.

Type A – Involves a vegetarian diet. You should stay meat-free and eat lots of beans and legumes, as well as whole grains. D’Adamo also advises that Type As stick to organic and fresh products because they have a more sensitive immune system.

Type B – Comprises a pretty strict diet of avoidance. You should stay away from corn, buckwheat, wheat, lentils, tomatoes, peanuts and sesame seeds. Chicken is also a problematic food and should be replaced by goat, lamb, mutton, rabbit and venison. You could also benefit from green vegetables, eggs, and low-fat dairy.

Type AB – Entails a combination of the Type A and Type B recommendations. Stick to tofu, seafood, dairy, and green vegetables. Avoid smoked or cured meats, as well as alcohol and caffeine as D’Adamo says Type ABs usually have low stomach acid.