An overweight chinchilla must receive a proper healthy diet and be able to run, jump and play. Maintain a strict no-treats diet and provide the animal with lots of space, height and obstacles to keep it engaged.
Chinchillas should weight between 0.9 and 1.3 pounds on average. Chinchillas that have gotten used to eating unhealthy foods are harder to impose a new diet on. Seventy-five percent of a chinchilla's diet should be hay kept available in its cage at all times. Don't neglect the animal's water. Drastically overweight and lethargic chinchillas should be taken to veterinarians who are familiar with the species to assess their health and outline a plan.