Fat virus

The fat virus is a theory that fatness in humans and other animals might have a viral source. The AD-36 adenovirus has been observed to increase the amount of body fat on laboratory animals, an effect that has been duplicated on chickens and monkeys. Human testing has not been committed on grounds of research ethics.

Although there is mounting evidence in favor of the theory, the notion of a "chubby-gene" was initially met with a large degree of scepticism, as there are many factors to consider when talking about human fatness: exercise, eating habits, other medical conditions, etc.