Before you ask, it’s pronounced like buckle. Buccal fat became the talk of some corners of the internet this week after social media users started speculating about celebrities who might have removed some for an extra-chiseled look.

Buccal fat is a type of fat found in the midsection of the face that can, in some people, make a face appear more rounded. Surgically remove some of that fat, and the face will immediately look more sculpted. Well, almost immediately. Initially, most patients experience some swelling, but once that goes down, it’s hello, cheekbones!

OK, one more time, what exactly is buccal fat?

“There are facial compartments that define the shape of the face, and there are superficial ones and deep ones,” Dr. Andrew Jacono, a New York City plastic surgeon best known for giving Marc Jacobs a face-lift, said. “Buccal fat is one of the deep facial fat compartments that kind of give structure to the cheek area.” It’s not affected by weight fluctuation, Dr. Jacono explained, “we’re born with how much we have.”

“There are some people who have a face that’s very sculpted, whether they’re cheekbones or more highlighted. There’s some people who have a more cherubic face. Some people call it chipmunk cheeks,” he added. He pointed to the faces of two cherubs, the round-faced angels on the bottom of the “Sistine Madonna” by the Italian painter Raphael, as examples of prime candidates for buccal fat removal.

Why are we talking about this now?

Blame Twitter and TikTok — and, inadvertently, Lea Michele. The “Funny Girl” star posted a glammed-up selfie on Instagram this week, which made its way over to Twitter where users speculated that Ms. Michele had the procedure done.

“Wake up babe new surgery just dropped in Hollywood jaw filler and buccal fat removal,” tweeted Agnes Philip, a 21-year-old computer science student in Florida who included images of Ms. Michele and other celebrities Ms. Philip believed had buccal fat surgery.

“They’re celebrities. Everybody sees the face every day, and they come back next week with a whole new face,” Ms. Philip said in a phone interview. She was surprised when her tweet went viral and noted in a subsequent tweet that this particular plastic surgery isn’t actually new.

And people are really removing this stuff?

Yes, plenty of them. “I’m doing three times as many buccal fat reductions this year than I was five years ago,” Dr. Jacono, who charges $40,000 for the procedure, said. (Other plastic surgeons say the procedure typically will cost between $7,000 and $16,000.)

Chrissy Teigen confirmed in an Instagram story in September that she had buccal fat removed. “Since I quit drinking I’m really seeing the results and I like it,” Ms. Teigen said, tagging her Beverly Hills plastic surgeon, Dr. Jason Diamond.

“I think of it as one of the classic celebrity secret plastic surgeries,” said Dr. Lara Devgan, a plastic surgeon in Manhattan. “These are all tiny tweak surgeries that alter facial features by 1 to 2 millimeters each that are omnipresent among public-facing people.”

What about those of us who aren’t public-facing people?

A quick search for buccal fat removal on TikTok will turn up no shortage of people who are documenting their buccal fat removal experience and their results in the following weeks, months and even years.

Tina Lee, a nurse who lives in Los Angeles, traveled to Tijuana, Mexico, in 2020 to have the procedure done. It cost $600. Her mom went with her and had the surgery, too. “It wasn’t painful, and the recovery was super fast for me,” Ms. Lee, 30, said. “They gave me pain medication, but I didn’t even need it.” She documented the trip on TikTok where it has been viewed 4.8 million times.

All right, I’m going to go watch some TikToks.

Be warned, though. Searching for these videos and watching even one of them will likely mean your For You Page, which suggests TikToks to users, will be haunted by them for days to come. If you didn’t already feel like everyone was talking about it, asking TikTok’s powerful algorithm to show you buccal fat will certainly convince you they are.

So what’s the procedure like?

Quick, actually. “This operation takes less than a half-hour,” said Dr. Alan Matarasso, the vice president of development for the American Society of Plastic Surgeons. “I can do it on a 20-year-old person at 8 in the morning, and they can be sitting at their desk at 9:15 with basically no discomfort and feeling like it was less involved than going to the dentist.”

Buccal fat can be removed using a local anesthetic. A plastic surgeon will use a scalpel to make a small incision inside a patient’s mouth to remove a fat pad the “size of a medium grape,” Dr. Matarasso said. The incision is then closed with dissolvable stitches. For typical patients, post-surgery pain and swelling is gone within a week. (If you’d really like to get into the gory details, you can watch Dr. Matarasso complete the procedure in this YouTube video.)

Ms. Lee said it took several months before her face felt fully back to normal, but she noted she had additional procedures done during her trip to Mexico, including chin and jawline liposuction.

What would I look like if I got it done?

For a rough idea, gently suck in through a straw and look in a mirror. Dr. Devgan recommends doing your best “Zoolander” impression.

What are the risks?

Bleeding is “the biggest problem,” Dr. Matarasso said, noting his patients follow a specific protocol before surgery, which includes not taking aspirin, to minimize this risk. He also noted the potential for nerve injury. Further risks, according to the Cleveland Clinic, include incision infection, facial numbness, and an asymmetrical face after the procedure is complete.

Does this surgery age well?

“Back in the olden days, doctors would remove the entire buccal fat pad, all of it. And then what would happen as you got older was you would look a little sunken in, like you’re sucking your cheeks in too much,” Dr. Jacono said. “We don’t remove the whole thing, we just contour the excess amount out.”

Still, multiple plastic surgeons warned the procedure was not for everyone. If you already have only a small amount of buccal fat to begin with, removing it can make your face look sunken and age you prematurely. “For the right patient, buccal fat pad excision can be quite beautiful, but if somebody is extremely thin or gaunt, you don’t want to overly hollow the face,” Dr. Devgan said. “In addition, if somebody has a moderate to severe degree of skin laxity, removing the buccal fat pad can make that worse.”

That laxity comes when skin loses collagen and elastin, two proteins in the skin that allow it to “snap back,” Dr. Devgan said. Older skin doesn’t snap back as well as younger skin. “When I’m doing buccal fat pad excision on, let’s say, a patient who is in their fifties or sixties, that’s usually in the context of a face and neck lift at the same time, because there is less elasticity,” she said.

Two years after her procedure, Ms. Lee said her face had changed a little since the initial results of the surgery, but she can still see a difference and thinks her face looks “slimmer.” “I feel much more comfortable getting my picture taken or even just like the way that my face looks with makeup,” she said. “No regrets.” Ms. Lee noted she had received negative feedback from commenters on TikTok who warn she will begin to look gaunt or saggy, but she hasn’t noticed this happening to her face.

Is this ever medically necessary?

Nope, purely cosmetic. Though having an excess of buccal fat can be uncomfortable for some people, particularly while eating, Dr. Jacono said.

Can it be reversed?

Technically, yes, but it will require multiple additional procedures, Dr. Jacono said. “Like all plastic surgery, doing it right the first time is important,” he said. “Undoing it afterward becomes a much bigger multistage surgery.”

Anything else I should know?

In addition to social media users speculating about celebrities who might have removed buccal fat from their faces, other users used the surgery’s sudden popularity to weigh in on the state of the beauty industry at large.

“What is buccal fat how are they still inventing new flaws for us,” Jules Zucker, a music supervisor who lives in Brooklyn, tweeted, using an expletive. Ms. Zucker’s tweet has been liked more than 100,000 times. “I am literally running out of limbs and features,” she added in a reply tweet.

“Life is too short to hate yourself. If something has been bothering you for years, and you have the resources to make yourself feel better about it, then, like, go for it,” Ms. Zucker, 27, said in a phone interview. “It’s the rapid fire trends that give me pause because, it’s like, they’re trends. Trends may be different in a year, but the only way you can reverse the procedure you did to your face is with another procedure.”

It Happened Online is a column in which we explain very particular bits of news enabled and amplified by social media.