Pilates has completely transformed the bodies of most of our clients. It comes from using the "powerhouse" and really focusing on and strengthening the abdominal wall, teaching it to lay flat with strength. If the stomach is sticking out, you're going to train it to stick out. In Pilates you're always thinking of this inward pull as if the navel is going in towards the spine and then lifting up slightly, pulling your abdominal wall very flat. In addition, there are long, fluid, larger motions that lengthen and stretch the muscles.
If you're consistent with it and make a commitment to yourself, you will see a change in your body.