You went on South Beach. You Zoned, Busted Sugar, gave Atkins a shot. Maybe you lost a little weight, maybe a lot. But chances are—and statistics predict—that sooner or later, it all came back. If diets don't do the trick, what does?

Writing it down—every bite you take, every vow you break. Yes, yes, you've heard it before, but I'm here to tell you that keeping a food journal works. Confessing what you've eaten, honestly and daily—even if it's only to yourself—gets the job done once and for all. O's editor at large, Gayle King, swears by it. So what can it do for you?

Why you should keep a food journal.