I'm not evaluating people, but I sure can evaluate health by what they eat or don't eat. At first glance, the notion that the same species has a different genetically programmed diet strictly based on blood type has some serious gaps in logic to say the least. I can't think of any species in which that is the case. You don't see random cows eating meat or cheetahs munching on berries.
Nearly all upper body disease and obesity is caused by a condition known as hyperinsulinemia. Essentially this is a chronically elevated level of insulin in the body causing insulin resistance. The more resistant the body becomes to insulin, the more we need until eventually the body becomes so heavily leveraged on it the pancreas can't produce enough on it's own - which then becomes type 2 diabetes. Insulin is the hormone used for storage that is produced by our body when we digest carbohydrates. When we digest protein, the body produces a hormone which regulates usage called glucogon. Fat is hormonally neutral when digested.
We are at the healthiest when our levels of insulin and glucogon are balanced - which isn't the case in 95% of western diets. It's funny that the French (and other Europeans) eat 10 times the amount of fat we do and have a fraction of the disease and obesity as us. In other words, the most important thing we can do for our health is regulate the amount of insulin in our body and stay away from fad "low-fat" diets - which is nearly impossible from a vegetarian / vegan standpoint.