Ancel Keys deserves the lion’s share of credit for convincing us that cholesterol levels predict heart disease and that dietary fat is a killer. Keys ran the Laboratory of Physiological Hygiene at the University of Minnesota and considered it his franchise, as he would tell Time magazine, “to find out why people get sick before they got sick.” He became famous during World War II by developing the K ration for combat troops—the “K,” it is said, stood for “Keys.” He spent the later war years doing the seminal study of human starvation, using conscientious objectors as his subjects. He then documented the experience, along with the world’s accumulated knowledge on starvation, in The Biology of Human Starvation, a fourteen-hundred-page tome that cemented Keys’s reputation. (I’ll talk more about Keys’s remarkable starvation study in chapter 15.)

Keys’s abilities as a scientist are arguable—he was more often wrong than right—but his force of will was indomitable. Henry Blackburn, his longtime collaborator at Minnesota, described him as “frank to the point of bluntness, and critical to the point of sharpness.” David Kritchevsky, who studied cholesterol metabolism at the Wistar Institute in Philadelphia and was a competitor, described Keys as “pretty ruthless” and not a likely winner of any “Mr. Congeniality” awards. Certainly, Keys was a relentless defender of his own hypotheses; he minced few words when he disagreed with a competitor’s interpretation of the evidence, which was inevitably when the evidence disagreed with his hypothesis.

When Keys launched his crusade against heart disease in the late 1940s, most physicians who believed that heart disease was caused by diet implicated dietary cholesterol as the culprit. We ate too much cholesterol-laden food—meat and eggs, mostly—and that, it was said, elevated our blood cholesterol. Keys was the first to discredit this belief publicly, which had required, in any case, ignoring a certain amount of the evidence. In 1937, two Columbia University biochemists, David Rittenberg and Rudolph Schoenheimer, demonstrated that the cholesterol we eat has very little effect on the amount of cholesterol in our blood. When Keys fed men for months at a time on diets either high or low in cholesterol, it made no difference to their cholesterol levels. As a result, Keys insisted that dietary cholesterol had little relevance to heart disease. In this case, most researchers agreed.