She may have an untreated thyroid problem. I thought maybe pregnant, and while it is possible, she looks plain fat too. I think they are a little like people though. Some dogs have a high metabolism, and you can barely keep weight on them. Others will plump out if given enough food. They say that speuter can cause them to plump up. But it should not happen if you continue to feed them properly and exersize, if they slow down a little, feed less. On the other hand, having a litter of pups sometimes puts weight on a bitch -- usually the thin bitch. After whelping and raising a litter, some bitches maintain a heavier weight.
The people in this add should be charged with neglect. If you want to be fat and allow it to effect your health and lifestyle, that is one thing, but letting a dog get extremely overweight is cruel.