Sure enough, carnivorous animals never grow fat (consider wolves, jackals, birds of prey, crows, etc.). Herbivorous animals do not grow fat easily, at least until age has reduced them to a state of inactivity; but they fatten very quickly as soon as they begin to be fed on potatoes, grain, or any kind of flour. ... The second of the chief causes of obesity is the floury and starchy substances which man makes the prime ingredients of his daily nourishment. As we have said already, all animals that live on farinaceous food grow fat willy-nilly; and man is no exception to the universal law. 