Tuna
Tuna is a low-calorie, high-protein food. No wonder the Japanese swear by it and it is sold there for ridiculous prices. Just visit the fish markets in Tokyo or Sri-Lanka to get an idea of its popularity. It is lean fish, meaning it is low in fat. Better eat the fresh ones instead of canned tuna whenever possible.
Tuna is popular among bodybuilders and fitness models who are on a strict regime and need their body to recuperate fast. As it is a great way to increase protein intake while keeping total calories and fat low. If you are trying to emphasize protein intake, make sure to choose tuna canned in water, not oil. Especially after your workouts.