Hi, both of my girls have the saggy belly syndrome (both are spayed). Tipper (gray-white tiger) got a little over weight after we first got her and we did free feeding and then developed quite the saggy belly after her spay. Now she not overweight but she still has quite the saggy belly still. Professor is a tiny little thing but has developed a saggy belly in the last three months even if shes at normal weight. So i wouldnt be worried about it!
Tipper and Proffy's mum, Anjya