My blood type is a+ is it really better for me to be vegetarian to be healthy and to lose weight ?

Good for any type: It may be healthier to be mostly vegetarian and to lose weight, but that is unrelated to a person's blood type. A person of any abo/rh blood type will benefit from eating vegetables.

That's baloney: Your blood type has no relationship to your best diet or to your overall health. This whole business was made up by a crook in the 1990's to sell books. Becoming a vegetarian is a moral choice rather than one that will improve your health -- the best studies show no real impact when you control for the fact that vegetarians tend to have other healthy habits.