Getting back in shape after childbirth: the best diet after pregnancy. Getting back in shape after childbirth is a goal that every new mother rightly wants to achieve. To do this, you need to choose the right foods, make an active life. And above all do not be in a hurry. It will take, in fact, some months, at least 9, for the body to return to being tonic as before. After giving birth it is more difficult to lose weight. Because the body due to the absence of the cycle is led to accumulating stocks to compensate for the increased energy requirement also determined by breastfeeding.