My parents have about five dogs and one dachshund was getting so fat her belly was dragging.   I watched her and saw she was going around eating all the other dogs food at mealtime so I would pen her with her portioned food until everybody was done eating.  I had almost got her down to a healthy weight before my mom whined that it was "mean and cruel" so I had to stop. Dog got fat again right away.  Mom and dog are still fat.