When someone is described as having a curvy body the term curvy stands for the shape of the person's body. However, it does not have a meaning that relates to weight but it is about the structure of the body.
When someone says that a woman has a curvy body...it does not mean that she is overweight....although an overweight woman can still have a curvy body...it just means that the woman has a bigger chest and a waist that is smaller than her hips...and her hips are broad! It is also called the hourglass figure! :D