A foodie is a person who has an ardent or refined interest in food, and who eats food not only out of hunger but also as a hobby. The related terms gourmet and gourmet define approximately the same thing, that is, a person who enjoys food for pleasure. A food enthusiast is essentially someone who treats food as a hobby and not simply as a way to survive. They are looking for the best food they can get, without settling for anything.
People who go to restaurants with 3 Michelin stars are probably food lovers.