Of course, not everyone fasts for political or religious reasons. Some people occasionally fast just because it makes them feel better. The American writer Mark Twain thought fasting was the best medicine for common illnesses. Whenever he had a cold or a fever, he stopped eating completely. He said that this always made his cold or fever go away Another American writer, Upton Sinclair, discovered fasting after years of overeating, indigestion, and headaches. His first fast lasted for 12 days. During this time, his headaches and stomach aches went away. Sinclair said that fasting also made him more alert.