I think it depends on what you define as a "flat tummy." I look at BD videos on youtube religiously and it seems that I see more tummies that are not flat than those that are, but then many of the videos I watch are performances and people's own stuff and not made for t.v. necessarily. I think that BD probably memics real life, which is that a small percentage actually have the perfect body, etc.
One thing I actually LOVE about BD is that any size woman can do it and it looks beautiful. Not just skinny ones with perfect flat bellies! ;0
But, if you are looking to achieve a flat tummy, try incorporating different ab routines into what you already do, such as reverse crunches.
