I have read that you need to be 18-22% body fat in order to see any of the work you do on your abs. I think this is right, your belly can look good without being in that range but in order to see the definition you must be very small. When I was ideal weight and I was toned everywhere but my belly was just soft it was because I wasnt in that percentile. I think alot of it has to do with your body type also, genes. Some people carry more weight in the abs that would be me and so even slim still no definition. Just work your abs off and see what your made of