Doing exercises to rid certain parts of your body of fat unfortunately doesn't work. It's called spot reduction, and our body doesn't work that way. You see, fat loss is a total body process, and where it comes off first is determined largely by the genetics we have... not the exercises we do.
This means that while ab work will strengthen your core, it'll give you a nice six pack... under the fat. The fat will stay put until it burns off over the rest of your body. Your muscles draw their energy from the bloodstream, not the surrounding fat stores, and generally, the places we tend to hold it the most prominently will be the last places we lose it.