This is the story of a morbidly obese man that is addicted to food. He has become trapped in his apartment due to his weight, and at the start of the book is going to be removed by crane to go to the hospital and have his foot amputated. This goes wrong however when everyone else seems to turn into rage filled zombies.
He ends up amputating his own foot, and surviving on the fat stores in his body. He does have a dog however, and had been using a drone to send it to a nearby field to exercise. After the incident he is doing this in the hope that his dog will feed on the rats in the field. This goes wrong after a few tries, and this ends up being the thing that causes him to finally leave the apartment.
It was pretty ridiculous to be honest, though I found the central character well written.