In 1988, the surgeon general, C. Everett Koop, proclaimed ice cream to a be public-health menace right up there with cigarettes. Alluding to his office's famous 1964 report on the perils of smoking, Dr. Koop announced that the American diet was a problem of “comparable†magnitude, chiefly because of the high-fat foods that were causing coronary heart disease and other deadly ailments. He introduced his report with these words: “The depth of the science base underlying its findings is even more impressive than that for tobacco and health in 1964.†That was a ludicrous statement, as Gary Taubes demonstrates in...