Estrogen helps to change the way in which fat gets stored so that it is less likely to be stored around the waistline and more likely to get stored in glutes and thighs especially, as well as face, breasts and upper arms. There is no migration of fat, rather fat just gets stored less in some areas and more in other areas. Insulin is also an important regulator of fat storage and can increase fat accumulation in the belly. Carbs stimulate insulin. Stress, with chronic high levels of cortisol can also cause fat accumulation in that area.