The length of time a cat can go without food depends on the individual, but the average is between 2 and 10 days. However, it is best not to allow a cat to go more than 24 hours without eating to prevent serious organ damage.
According to the Feline Nutrition Education Society, cats which go long periods without food generally die from a condition known as hepatic lipidosis, also known as fatty liver disease. This disease can occur very quickly, and even if it is caught early, it is often irreversible. Overweight cats are at a higher risk of getting hepatic lipidosis than fit cats, although all cats get it if they go long enough without food.