This dissertation explores the adaptation of popular American diet programs to the treatment of chronic disease after the Second World War. Situated at the intersection of food studies and medical history, this project traces the rise and fall of four distinct dietary movements through the biography of their respective diet guru(s)-Alvenia Fulton (1907-1999), Michio Kushi (1926-2014), Nathan Pritikin (1915-1985), and Robert C. Atkins (1930-2003). Unlike the conventional portrayal of diets as weight loss fads, the diets featured in this dissertation were predominantly oriented toward longevity and disease reversal. I argue that, accompanying the rising tide of skepticism toward expert credibility of all kinds in the 1960s, diets became a potent alternative to the health practices and conventional treatments espoused by hegemonic nutritional and medical authorities. To the chagrin of federal regulators and the spokespeople of scientific nutrition and medicine, diet programs openly flouted scientific consensus and official nutrition standards and instead forged strong connections with and mirrored the claims and practices of alternative and complementary medicine. The four dietary movements featured here developed lasting legacies in our contemporary wellness culture.