The Prolon starvation diet —which promises to “put your body into a protective and stress resistant mode; remove damaged cells and tissues; and promote self-repair through cellular regeneration and rejuvenation”—is all the rage in Silicon Valley. It’s sold in 15 countries and has been tried by more than 150,000 people. That’s 150,000 people who paid $250 to starve themselves for 5 days. Go figure.