I know you've heard that when you strength train, you burn fat and calories. Here is a breakdown I've heard that makes it make sense.
When you do an exercise (let's say a sit up), you are creating tiny tears in that muscle. It burns calories to repair those muscles, and then it also burns them to maintain those built up muscles (please note, built up does not mean bulk up).
However, those calories are NOT just coming from the fat storage on top of your abs. It comes from your entire body. That is why you cannot spot reduce.
The more you workout, the more muscle you build (whether it be bulky muscles or lean and toned muscles), the more calories you are burning to repair and maintain those muscles.
So to answer your question, situps will not only target the fat on your stomach, it will go to the "all around" fat loss. However, I definitely notice that after doing a lot of core work, my abs look more toned even with a layer of fat still on top! So they are definitely worth doing
7/1/13 My Goal: to be 150lbs! for every mini goal met
Mini goal 1: 160 (my lowest consistent weight)
Mini goal 2: 156 (my lowest adult weight EVER)
Mini goal 3: to SEE 150 (New territory!!)
GOAL: To have a fluctuation be UNDER 150