The 4-Hour Body: An Uncommon Guide to Rapid Fat-Loss, Incredible Sex, and Becoming Superhuman is a nonfiction book by American writer Timothy Ferriss.

The diet prohibits starches and all things sweet (including fruit and all artificial sweeteners), with strong preferences for lean protein and a few specific vegetables.

[citation needed] The Harvard Business Review quoted Dr. Tieraona Low Dog: "many people will lose weight if they follow it, though I don't think that the diet is capable of all the claims in the book."

[1] U.S. News quoted Scott Kahan (codirector of the George Washington University Weight Management Program) describing it "as another cockamamie fad diet" and expressing doubts about its sustainability.

[6][7] Ferris describes a detailed marketing plan for promoting the book, including trailers, aggressively seeking out fitness and exercise bloggers and influencers, and prizes for readers who bought The 4-Hour Body package deals.