I have a lot of saggy skin on my tummy due to serious pregnancy and surgery damage. I used to assume that no matter what I did, my stomach would always look awful. But in the last year or so I learned two things. One that you can fill in at least some saggy skin by building muscle. Two that a lot of what I assumed was saggy skin was actually subcutaneous fat. Fat can sit very unevenly in areas where the skin was damaged, so even though it seems counter-intuitive, losing any existing excess fat can actually improve the wrinkly appearance.