The year 2021 will see the 50th anniversary of Nixon’s declaration of the war on cancer, but a victory celebration does not appear to be in view. Dr. Richard Feinman suggests this may be due to an overemphasis on the somatic mutation theory of cancer and insufficient attention to the metabolic approach to understanding the disease. Here, he explains Otto Warburg’s research on cancer cell metabolism, breaks down the processes that shape healthy energy metabolism, and describes why scientists believe the ketogenic diet may have anti-cancer effects.