A person who eats human flesh is called a cannibal.
Vegetarian or a Vegan
A person who eats a mixed diet of plants and meats is a omnivore.
Cannibalism.
Gannet
A person who eats animal flesh is commonly referred to as an omnivore.
A vegetarian.
A slimming diet
What is eaten is food.
A person that eats all the time is called greedy. If you know a person that eats all the time, it's likely they will get fat. If they don't get fat and they eat all the time, then that is just the way they were born. edit- greed is where you want and keep everything for yourself where as if you eat a lot you would be called a glutton
Groups that practice eating other humans, as food or as a ritual, are called "cannibals". The practice is "cannibalism".
A person who eats only one type of food is called a monophagist.