Richard Simmons is gone.

His fitness studio in Beverly Hills is shuttered. On its stoop is a sun-bleached edition of the Beverly Hills Courier from January. Inside are piles of debris, tongues of pink insulation, a dusting of pulverized wallboard on the ballet barres. In the middle of it all, there’s a forlorn scale where his students measured pounds sacrificed to the oldies.

“I knew him very well, but I don’t know what happened to him,” said Germen Helleon, the proprietor of a hair salon next door.

On Feb. 15, 2014, Simmons did not show up to teach his regular exercise class at his studio, which was called Slimmons. He cut off contact with friends and hasn’t been seen in public since.

A short drive up into the Hollywood Hills is the Simmons manse. The lace curtains are drawn. A red van of star-seeking tourists idles briefly, barely stopping. In the past, Simmons would scurry out of his house to greet the gawkers. He was a particularly friendly mammal on the Hollywood safari.

Now, nothing. There’s something colorful in the window at the peak of the house. Balloons? One of his many feathered costumes? Is he up there, in the attic, watching us now?

One of his regular students was Dan Taberski, a former producer for “The Daily Show.” He has launched a podcast called “Missing Richard Simmons.”

“I think he’s important,” Taberski says in Episode 1, justifying his loving invasion of Simmons’ privacy.

Simmons, 68, is a true original whose commercial sorcery summoned the forces of positive thinking. He cast his spell using old-fashioned showbiz techniques that he likely picked up from his parents, a retired vaudeville duo. Watch his low-impact aerobics on YouTube and see a retro antidote to the bleeding palms of generation CrossFit.

A boom, then a bust

America hasn’t had much use for Simmons over the past 20 years, but the 20 years prior saw a remarkable run.

In 1975, he opened a health food restaurant in Beverly Hills named Ruffage, with an adjoining fitness studio. The clientele included Paul Newman, Diana Ross and Barbra Streisand. He would run at fat customers and chant, “Thighs, thighs, go away, give them all to Doris Day!”

He became a go-to guest for Merv Griffin, Mike Douglas and Phil Donahue. “The Richard Simmons Show” debuted in 1980 and within a year was airing on nearly 200 stations. It featured comedy sketches, exercise sessions and audience discussions about prenatal nutrition and hyperactivity in children.

In 1980, he wrote “Richard Simmons’ Never-Say-Diet Book,” which was a bestseller for over a year. The “Sweatin’ to the Oldies” videos started coming out in 1989 and featured average, overweight Americans doing aerobics alongside Simmons.

“I work for the underdogs,” Simmons told the Toronto Star at the time. “I adore Jane Fonda, [but] she has Stepford Wives with perfect bodies. I use real people.”

The second “Sweatin’ to the Oldies” tape sold 1.5 million copies, rivaling Fonda’s “Workout.” Simmons claimed that over his career, he helped the world lose 12 million pounds.

But even at the height of his success, he remained something of a punchline. David Letterman pranked him during dozens of appearances. Howard Stern needled him until he fled the studio in tears.

A month and a half before he disappeared, Simmons was on CNN to talk about a new dance song called “Hair Do.” Anchor Brooke Baldwin asked, “What do you say to yourself in the mirror in the morning?”

Simmons pursed his lips and looked away from the camera. His eyes moistened. “I say, ‘Try to help more people,’ because there are more obese children and teenagers, young adults and seniors in the world right now — more than ever in the history of the United States,” he replied.

Six weeks later, poof.

What happened?

There have been rumors and conspiracy theories about his disappearance, ranging from speculation that his knees are shot and he can’t bear to be seen enfeebled to stories that he’s being held hostage by a longtime housekeeper who is, supposedly, a witch. While in his prime, Simmons talked often about the depression he faced as an obese teen, leading many fans to conclude that he’s battling a mood disorder.

Los Angeles police did a welfare check on Simmons and reported that “he is fine ... He is doing what he wants to do, and it is his business.”

A year ago Simmons called the “Today” show to squelch the rumors. His voice, normally a joyous squeal, was soft and quiet. He was healthy, he said, and under no one’s control.

“I just sort of wanted to be a little bit of a loner for a while,” he told Savannah Guthrie. “Right now, I just want to sort of just take care of me.”

And then, unprompted, he gave a clue to his emotional whereabouts. “Survival has always meant a lot when you’re an overweight kid and you’re made fun of and you’re put down,” Simmons said. “Some of that stuff never leaves you, Savannah. It’s sort of like a shadow, like Peter Pan.”

In his podcast, Taberski asks rhetorically if Simmons has the right to vanish. Yes, Taberski says. But that doesn’t stop people from missing him.

“What we’re doing is something of a grand gesture,” Taberski, 43, said. “We are reminding him that what he did was important and that he helped countless people and they love him for it. There’s something about him, maybe, that he doesn’t believe, and hopefully this will jar that part of him.”

Taberski doesn’t know how the podcast will end. But he recalls a promise Simmons made during his “Today” interview. “Not to worry, Richard’s fine,” he said. “You haven’t seen the last of me. I’ll come back, and I’ll come back strong.”