EVERY spring, as sure as cherry blossoms bloom, so does the notion that women should diet, exercise and even liposuction their way to bikini-ready bodies. Magazines like Shape and Self reinforce the idea that preparation is essential, with months-long bikini body countdowns (100-calorie snack tips included) and workout DVDs like “Bikini Ready Fast!” as if the beach reveal were a test on par with the MCAT and only a slacker would settle for a one-piece.

“It really sends the message that you’re not worthy right now to put on a suit,” said Malia Mills, a swimsuit designer whose brand’s motto is “Love Thy Differences.” Ms. Mills, 44, said shoppers often declare in one of her 10 stores: “I just wanted to see what you had. I’m coming back when I lose five pounds.”

As our culture increasingly enshrines physical perfection, the bikini has come to inspire dread and awe. It wasn’t always so. In the 1960s, when bellybutton-baring suits first became popular in America, “it was a youthful phenomenon definitely,” said Sarah Kennedy, the author of “The Swimsuit: A History of Twentieth-Century Fashions.” Then the high-fashion set and movie stars began to put on bikinis, and by the ’70s, she said, the bikini was “worn by all ages.”

And a few extra pounds didn’t disqualify anyone, considering the fitness revolution was still roughly a decade away. (In the book there’s a 1940s photograph of a fresh-faced still-brunet Marilyn Monroe looking smashing in a blue-and-white striped two-piece, a roll of pale flesh at her midsection.)