You will lose a pound if you burn 3500 more calories than you take in. This is one of the bottom lines in weight loss but whether or not you are actually burning 3500 calories varies from person to person with the same activity.
A dog can survive without eating for 14 days, procided day wouldn't be in good shape and health.
How long can a dog go without water? The Pet Shed Petcyclopedia explains that a flea can live for a little over 130 days when it has access to a host. When a flea loses its host, it must find a new one as quickly as possible. According to 1-800-PetMeds, a little over half of newborn fleas may be able to survive for two months without a host if their environment is humid enough.