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Imagine a quick, nonsurgical procedure that could reduce stubborn areas of fat. It’s virtually painless, touted as safe, and has zero downtime. Sound too good to be true?

Meet cryolipolysis. Also known as fat freezing or CoolSculpting, the FDA-cleared procedure uses a wand-like device to break down fat cells with cold temperatures through 40–60 minute treatments. People start to see results just a few weeks later, finally seeing the size of the area shrink by about 25 percent six months after the procedure.

But a very small portion of patients experience the exact opposite effect: The areas targeted by cryolipolysis actually become larger and firmer. And new research shows that the complication, known as paradoxical adipose hyperplasia (PAH), might actually be more common than experts previously thought.

What’s the risk?

In a paper published in the most recent issue of the medical journal Plastic and Reconstructive Surgery, researchers discovered that PAH occurs in about 1 out of every 138 cryolipolysis treatments. That rate is much higher than the manufacturer’s estimate of 1 out of every 4,000 treatments, according to the researchers.

Both the study and the manufacturer measured the rates of PAH based on a treatment cycle, defined as the use of cryolipolysis on an individual spot on the body. However, those numbers don’t reveal the risk of this complication on the per patient level, as people typically get multiple spots on their body treated at one time, said Dr. Jonathan Kaplan, a board-certified plastic surgeon at Pacific Heights Plastic Surgery.

“If a patient who had six spots treated gets PAH in one spot, then that’s 1/6 according to [the way the manufacturer and researchers measure the rate of incidence],” he said. “But in terms of what people really care about, the truth is the patient has a large swelling — they don’t care that it’s only 1 spot out of 6. They should use the number of patients, rather than the number of cycles, that have PAH as the denominator.”

Even though the new data suggests the per-treatment incidence of PAH is 0.72 percent, the actual risk on a per patient basis is likely higher, said Kaplan. A representative from Allergan, the manufacturer of CoolSculpting equipment, said the company has no means to track the number of patients affected by PAH.

“We do not disagree with [Kaplan] that it would be ideal or more relevant to report by patient, but unfortunately the data does not exist in our records,” said Brad Hauser, vice president of research and development and general manager for CoolSculpting at Allergan.

The risk of developing PAH at a cryolipolysis site is still quite low, coming in at less than 1 percent. Still, doctors have yet to determine the exact risk factors for this complication.

Who develops PAH?

“No one’s really sure why PAH happens,” said study co-author Dr. Michael Kelly, a board-certified plastic surgeon at Miami Plastic Surgery. “Something is triggering the fat cells to grow, and I think the cold is creating inflammation. For most patients, that will cause the fat cells to go away, but in a small group, the fat cells grow in response to the cold.”

The good news is that PAH can be treated with liposuction after a few months, and the manufacturer of the cryolipolysis equipment usually pays for the procedure, said Kelly. However, doctors must explain the treatment options with extreme sensitivity, as patients are “initially aggravated” by the delay and the need to undergo cosmetic surgery they hadn’t originally wanted, according to report.

“You definitely have to be sensitive. These people were getting the cryolipolysis treatment to avoid surgery in the first place. Now you’re telling patients they need to have surgery. It’s a difficult conversation,” said Kaplan.

Overall, cryolipolysis is considered a safe procedure by the medical community. If you’re thinking of trying it, work with a dermatologist or cosmetic surgeon to determine whether you’re an ideal candidate. The biggest thing to keep in mind is that it’s intended to reduce the number of fat cells in an area and change its shape, not help you lose weight.

“The effectiveness of the procedure also depends on the elasticity of your skin, so that when the fat is taken away you will shrink down,” said Kelly. “The best candidates are usually people at an average weight or slightly heavier who have good-quality skin and fat in a specific area that they want to change the shape of.”

Whenever you’re considering a medical procedure, it’s always a good idea to discuss potential complications with your doctor. The findings about PAH and CoolSculpting have inspired Kaplan to have deeper conversations with patients about their risk.

“I do think CoolSculpting is safe overall, that’s why I continue to offer it,” he said. “But whereas in the past we might have just let the consent form do the talking, now we’re more proactive in telling them about things that are still rare, but slightly more likely to happen.”