What is the bestt food for diet?

Balanced Combination. Rather than going on a diet, make a lifestyle change! this will help you manage your weight in the long run & will be less likely to gain it back like most on diets do. Eat 3-6 small meals/snacks--balanced combo of fruits, colorful veggies, lean protein (fish/chicken), grains (wheat, rice). Try to avoid processed/boxed/sugary foods. You don't have to cut them out completely, save them for a treat.
Water protein fiber. You can fool your stomach into thinking it has food in it by keeping it full of water (not diet soda). Also you stay satisfied much longer after a meal if you concentrate on protein (meat, nuts, eggs, cheese) and cut out as many carbs (potatoes, rice, pasta, etc.) as you possibly can. These take longer to digest and therefore leave the stomach more slowly. Same with fiber (bran, vegs pgf).