This is the era of ever-shrinking men’s trousers — they are tailored and shorter, tighter and shrunken, too tight and too short. And even occasionally veering into: Pitbull, exactly how are you breathing in those high-­waisted white pants?

The look of menswear changes at a snail’s pace, and sometimes it takes years before a not-at-all outlandish idea trickles from the runways, which are now hosting the spring 2015 collections, to the mass market. But when a fashion idea finally reaches the vast middle ground, it tends to stay a while, putting down roots in the menswear landscape.

Thus we are deep in fashion’s equivalent of an old-growth forest — surrounded by men in aggressively tailored pants.

The ubiquity of this trend, even in offices far away from the expected crucibles of creativity, had an executive at a Maryland real estate development firm recently marveling, with some chagrin, that the men in her office were given to wearing particularly close-fitting trousers, which she described as “tight.” While that is a judgment call, it’s true that the cut of men’s pants — the more fashionable cut, that is — has gotten snugger, much snugger than what it was back when Giorgio Armani’s loose Italian tailoring defined power and President Bill Clinton was wearing roomy Donna Karan suits.

The modern suit, from Saint Laurent to J. Crew, now comes with narrow, flat-front trousers, falling straight without a break, sometimes cropped enough to reveal more than a smidgen of bare ankle. The jacket is single-breasted with a notched lapel. The proportions are particularly noticeable on red-carpet celebrities whose suits and tuxedos tend to be custom-tailored to the last millimeter, particularly if that suit is by designer Tom Ford and is worn by the likes of Justin Timberlake, Colin Firth or Bradley Cooper.

Fashion trends for men's pants have changed quite a bit over the years, from denim in the 1950s, to parachute pants in the 1980s, to skinny jeans today. Here's a look at how men's pants have evolved throughout the decades — good, bad and ugly. (Jhaan Elker/The Washington Post)

Cooper, by the way, caused a media fuss when he wore distractingly tight tuxedo pants to a White House state dinner. His self-described “crazy-town tight” trousers, he later explained, resulted from having packed on pounds for a film role. His was a fashion faux pas, not a fashion statement.

“A slim-fitting suit should skim the body, not hug it,” warns fashion expert Tim Gunn. “It’s not intended to be a wet suit!”

On the average man, the popular cut — done right — could most accurately be described as lean. The preference for this style crosses ethnicities and economics. It is embraced by 20-somethings, as well as men in their 50s.

But trim trousers have little mercy for beer bellies or two-fisted love handles.

“I started to get in shape in 2005, and the cut basically suited my frame,” says Matt Martinez, senior producer of NPR’s “All Things Considered,” as he explains his journey to the narrow silhouette. “I went shopping and I was looking at the same kind of clothes that I used to buy, and they were really balloony. I went looking for clothes that fit better. It was actually kind of hard to find really fitted clothes back then unless it was something bespoke.”

Martinez, 38, a fashion aficionado but also a frugal man, was ahead of the mainstream market. And he was not looking in the expensive designer realm. Had he wandered into the land of $3,000 suits, he would have found that Ford was one of the lead instigators in the tight tailoring movement during his time at Gucci in the early 2000s. And now, designing under his own name, he has little tolerance for surplus fabric. Hedi Slimane at Dior Homme also popularized razor-sharp cuts that could be worn only by men whose natural metabolism roared like an inferno or those who simply did not believe in food. Miuccia Prada pushed the trend along with her fondness for boyish models who were so wispy they looked as though they couldn’t bench press a sparrow. And Thom Browne chopped his Ivy League slacks at the ankle, further decreasing the amount of fabric dedicated to the average pair of trousers. Finally, the widespread popularity of skinny jeans meant that a host of young men were accustomed to pants that looked a lot like a pair of jeggings.

“I made the switch probably seven or eight years ago,” explains Bethesda-based real estate agent Gregg Zeiler, 52. “I started with Ralph Lauren — with his Black Label line. He made a flat-front [pair of pants] that sat on the hips, not at the waist.”

There was no fighting it. There was no point. Close-fitting pants were everywhere, and generally, they looked good.

“I think no matter what, a guy will always look good in tapered pants,” says stylist and GQ contributing editor Brian Coats. “But they shouldn’t be so tight everyone is looking at your jewels.”

Jimmy Fallon, host of “The Tonight Show,” has mocked such shrink-wrapped packaging, most recently with a tight-pants smackdown featuring Jennifer Lopez. “Everybody’s talking ’bout my tight pants,” Fallon chirped, as he gyrated in tiny white jeans. “Everybody’s looking at my tight pants.”

Fallon’s joke, however, was accompanied by a knowing nod and no small amount of fashion savvy. He “likes things pretty fitted,” says Coats, who works as his stylist. “He’s super into looking fit and cool and slim. And he realizes a slim fit will do that.” In “The Tonight Show’s” opening credits, for instance, Fallon is running through the streets of New York in a navy suit by Saint Laurent, where Slimane is now creative director.

“He’s super into fashion,” Coats says of Fallon, “but he doesn’t want to look like it.”

In that way, Fallon is like a lot of men. They don’t want to look like they’re trying too hard. Even Zeiler confirmed: “I try to look effortless.” The slim suit is a perfect trend, especially for Washington. It’s a way to signify stylishness without a lot of bells and whistles.

Men’s attitudes have changed as well, says Memsor Kamarake, stylist and former fashion director of Vibe magazine. Machismo is no longer about puffing oneself up and taking up as much physical space as possible. At one point, male models with 29-inch waists used to ask for 36-inch pants for Vibe photo shoots. In 2007, even fashion-savvy male models sneered at the arrival of leggings, Kamarake says. Now self-proclaimed fashion god Kanye West wears them with leather kilts.

For most men, it took some time to get comfortable with the narrower silhouette, for their eyes to adjust. Some guys continue to struggle with it. Coats will sometimes style athletes for GQ — average Joe types, not the fashion cognoscenti like Tyson Chandler or Dwyane Wade — and outfit them in slim-cut pants. A hovering manager will ring an alarm: You’re wearing skinny jeans!

Well, no, Coats explains. But for a lot of men, any silhouette that’s actually on speaking terms with their body is synonymous with one that’s tight.

As the mass market has embraced the leaner silhouette, uncomfortable extremes and just plain bad ideas have come to the fore. For example, there are those who go too far: Men who want their trousers taken in to the last binding inch; those who want a suit jacket with a waistline that fits like a corset.

And under the category of bad ideas: “There’s that weird hybrid that happened: a slim jean that sometimes sags. And you get this waddle” as you walk, Kamarake says.

Mostly though, slim has been good. It has flattered the average man’s physique. But now that this aerodynamic silhouette has been popularized, menswear is moving on. The runways in Europe have been proselytizing the merits of a boxier, looser fit. It’s roomier through the thigh, with a tapered leg and a cropped hem. Sometimes, it’s practically ninjalike.

But outside niche markets, loose remains a tough sell. “I think slim is just more flattering,” Martinez says. “I see double-breasted on the runway, too. And it gives me shivers in a bad, bad way. I don’t like the boxy look. I can’t see myself moving in that direction.”

Well, at least not now. Menswear moves slowly, but, like the rest of fashion, it does eventually move.

“It’ll change again and everyone will be wearing palazzo pants,” says Simon Doonan, creative ambassador of Barneys New York.

“And then we’ll be longing for the days of tight pants.”