Why sumo fighters are fat its there a relation between them and how Buddha looks?

Japanese sumo wrestles attain great weight to make themselves difficult to toss around. However there is a lot of muscle, not fat involved. The weight gain is achieved through a high protein diet and exercise.

Buddha (the Indian philosopher) advocated a middle way in your approach to life, part of this is to eat until you are no longer hungry - not until you are full. Combining this with a vegetarian diet and a lifestyle which involved walking about giving his discussions or sermons, it is likely that he was fit and slender not fat.

As far as the non-Buddhist view that Buddha was fat, this is probably due to the fact that most people's only contact with Buddha images is Hotei, the fat laughing oriental figure often seen in restaurants, or the fat Buddha seen in Hollywood movies.