A possible explanation: Fewer people are dieting because there's no exciting "It" diet on the scene. Back in 2004, the top-selling diet book in the country, "The South Beach Diet," sold 2.4 million copies, according to Nielsen BookScan. In 2007, the most popular book, "You: On a Diet," by Oprah Winfrey's health guru Dr. Mehmet Oz and Michael Roizen, managed a mere 706,000 copies. Last year's top selling book, "Eat This Not That!" sold a mere 552,000 copies by September, and is more reference than diet book.
Take a look back at popular "it" diets.