Hi Ingrid, thank you for your question. There is not a pre-determined amount of pounds which impact skin laxity. Every body is different, that includes skin.
Sagging in the abdomen is especially common in the lower "pooch" area after considerable weight loss, or pregnancy in some cases. Diastasis recti, which is the separation of the abdominal muscles which can result from pressure due to pregnancy or weight gain is only corrected with Tummy Tuck surgery.
Best of luck to you!