For much of human history, people didn't know that much about infectious diseases and the body's mechanisms for fighting them. Perhaps the first healer to use diet to fight disease was fourth century B.C. Greek philosopher and physician Aristotle, who theorized that nutritional excesses and deficiencies caused various illnesses. Aristotle thought that food was to the body like wood is to a fireplace, and that the more you ate, the higher your temperature would rise. Instead of starving a fever, though, Aristotle instructed fever sufferers to gorge themselves. He thought that would heat up the body so much that it would burn out the fever, the way that a burning forest overwhelms a campfire.
Though Aristotle's medical teachings were followed by Western doctors for many centuries afterward, eventually someone must have realized that gluttony didn't cure fevers. By the 1500s, feverish patients were being advised instead to fast, in the hope that depriving the body of fuel would cool their internal fire. The first published prescription came in 1574, when English writer John Withals observed that "fasting is a great remedie of feuer." Unfortunately, his medical expertise wasn't much more reliable than his spelling.
Nevertheless, by the 1800s, fasting -- in addition to other dubious remedies, such as bloodletting and swallowing castor oil to induce vomiting -- was an established fever remedy. In an 1884 article in the magazine Popular Science, physician C.E. Page confidently concluded that "where the 'fasting-cure' is applied in extensor, with appropriate water and air baths, sunshine and perfect ventilation, the worst forms of fever rarely have a 'run' of ten days -- three or four days will often suffice to insure convalescence."
By the late 1800s, the axiom had evolved into "Stuff a cold, starve a fever." Many people of that time thought that colds were the opposite of fevers and were caused by a drop in body temperature. So, it made sense that colds could be cured by shoveling more fuel in the bodily furnace. In an 1863 sketch, Mark Twain wrote of trying to cure a cold with a hearty meal at a restaurant. (It didn't work, and he got sicker.)
Did any of this fasting do anybody any good? We'll get into that in the next section.