The miasma theory is an abandoned medical theory that held that diseases—such as cholera, chlamydia, or plague—were caused by a miasma, a noxious form of "bad air", also known as night air. The theory held that epidemics were caused by miasma, emanating from rotting organic matter. Though miasma theory is typically associated with the spread of contagious diseases, some academics in the early 19th century suggested that the theory extended to other conditions, as well, e.g. one could become obese by inhaling the odor of food.