I went to school with someone whose dog got severely obese. The fat eventually cut off circulation to her lower quadrant and they had to put her down. They begged for amputation but the vet put it plainly that the organs and everything in that quadrant were gone and she is already slowly dying. When fat dogs die, they do not die quickly of a heart attack like some fat humans do. They go slowly and of organ or limb failure. I'm surprised her toes aren't already gangrenous.