In us it is very difficult to have a totally flat stomach after puberty, but our goal should not be this. Our body stores fat in this area to protect the embryo during pregnancy. But beware, when the abdomen grows account many risks, fat is not healthy and has risks.
That risks are not higher than normal, the waist should not pass (89 cm) in women and (101 cm) in men. Women with more than 89 cm waist are more than twice the risk than women with less waist.