Women sometimes are sold on the idea that exercises will lift their breasts so breast reduction or breast lift surgery can be avoided.
Exercise can lead to weight loss and weight loss can hep reduce breast fullness. This will not lift the breasts however. Sometimes weight loss will make the breasts droop more, but it will not lift them. Exercise does not tighten the skin.
I usually recommend that my patients get their weight into a range that they can maintain, then consider whether or not surgery might be a good thing for them.