What on earth is a sponge in the stomach? I have never head of it before. Im sorry but I don't understand your question. Is it possible to put a sponge in the stomach or are you referring to something metaphorically? Anyway, if you want to lose weight then the best way to do it is with the help of diet. Forget all this sponge nonsense and get yourself on a good diet and also make sure that you get plenty of exercise. Sweating it out is an effective way of losing weight an getting rid of calories in the stomach.