“It was the aesthetics,” he said, “like for everyone else.”

He first saw the bikes in Manhattan in 2007, he said, and returned to France enchanted by their clean lines, with plans to imitate. “I hadn’t even realized that it was a fixed-gear bike,” Mr. Zuzzé said.

But he has since come to love riding them: with a friend, he recently pedaled 1,000 kilometers, or about 620 miles, along the Danube, between Ulm, Germany, and Bratislava, Slovakia. (Their panniers loaded with supplies, in the lonely Czech countryside, the two “looked like anything but hipsters,” he said.)

The Parisian trend can almost certainly be traced to New York City. Like Mr. Zuzzé, many of Paris’s fixed-gear vanguard say they first saw the bikes about five years ago on visits to Manhattan (the city’s messengers have sped around on them for decades) before returning, covetous, to France.

As much design objects as means of transport, the sleek bikes do seem particularly appropriate to Paris and the sensibilities of the aesthetes who make up so much of the city’s population. And bicycles, in general, have exploded in popularity here since the 2007 launch of the Vélib’ bike-sharing program, bike-shop owners say.

“You take a seat on the Canal St.-Martin to have a morning coffee, and all you see are bikes going by,” said Alexandre Billard, who in 2007 opened biCyCle Store Paris, a spare and meticulously curated boutique in the Third Arrondissement.

One of several new specialty shops selling mostly fixies and fixie components, Mr. Billard’s store on a recent afternoon displayed cranks of at least 10 colors, including two shades of mauve, along with a selection of messenger bags, wood-framed sunglasses and Brooks England leather saddles.