Fat That Grows After Fat Freezing: A Multicentre Study

A multicentre study from eight Canadian clinics reviewed more than 2,000 people treated with cryolipolysis (fat freezing) to see how often a rare side effect occurred: treated fat becoming larger and firmer instead of smaller. This reaction, called paradoxical adipose hyperplasia, affected fewer than 1 in 200 patients, was less common with newer equipment, and in most cases was corrected with liposuction. For patients, the study offers a clearer picture of a risk worth understanding before treatment.

Why this was studied

Cryolipolysis cools fat cells under the skin so that some of them die and are cleared away over the following weeks. It is a popular non-surgical option for small, stubborn areas of fat. In a small number of people, though, the treated area slowly grows into a firm, well-defined bulge, often shaped like the applicator.

Early estimates of how often this happens came largely from manufacturer data and were very low. Clinicians suspected the true rate might be higher, partly because the change can be mistaken for weight gain or a poor result.

What the researchers did

The authors reviewed patient charts from eight Canadian medical centres that used one widely available cryolipolysis system between 2015 and 2019. Altogether, the review covered 2,114 patients and 8,658 treatment cycles, an average of about four cycles per person. Cases were diagnosed by plastic surgeons based on visible enlargement, firmness compared with untreated tissue, weight history and timing.

What they found

Nine patients developed the condition, about 0.43% of patients or 0.15% of treatment cycles. That is higher than the manufacturer's earlier estimate, although still uncommon.

Other findings included:

• Equipment mattered. Most cases came from older device units that were replaced in 2016. With newer units, the rate fell to about 0.11% of patients, a drop the authors describe as more than 75%.
• Men were over-represented. Five of the nine patients were men, even though men are a minority of fat-freezing patients. The authors suggest hormones may play a role, but this was not proven.
• It appeared slowly. On average, diagnosis came well over a year after the first treatment, with a range from about five months to nearly three years.
• Most people did not notice it themselves. Seven of the nine were identified at a follow-up visit, and many assumed the fat had simply come back.
• The abdomen was most common, but cases also occurred on the flanks, bra line and inner thighs. The authors did not find that any one area was riskier, and extra cycles did not appear to raise the risk.

Six patients chose corrective liposuction, and all six resolved. One had further fat-freezing cycles, which helped only partly, so the authors do not recommend that approach.

How strong is this evidence?

This was a retrospective chart review, meaning researchers looked back at existing records rather than following patients in a planned trial. That design is useful for estimating how often something happens across many clinics, but it has limits:

• Some cases may have been missed if patients did not return or the change was put down to weight gain.
• With only nine affected patients, conclusions about risk factors such as sex or ethnicity are tentative.
• Height was missing for most affected patients, so body mass index could not be assessed.
• The lead author disclosed a consulting relationship with the device manufacturer, which readers should keep in mind.

Even with these caveats, it is one of the larger real-world reviews of this complication, and its Canadian setting makes it relevant to patients here.

What does it look and feel like?

Unlike ordinary fat that returns with weight gain, this reaction tends to stay confined to the treated area. People may notice a firm, rubbery bulge that feels different from the soft fat around it, sometimes with a squared-off or applicator-shaped outline. It usually is not painful. Because it develops slowly, it can be easy to dismiss as a disappointing result, which is one reason the authors think it may be under-recognized. A physician can usually tell the difference by examining the area, comparing photographs and reviewing weight changes since treatment.

What it means for you

If you are considering fat freezing, this study supports a balanced view. Most people do not develop this reaction, but it is real, it can appear long after treatment, and fixing it usually means surgery. That trade-off is worth weighing, especially for men.

Practical points include:

• Ask what equipment is used and how long the clinic has used it.
• Take dated photographs and keep track of your weight, so changes are easier to judge.
• Attend follow-up visits, since many cases were found that way.
• Report any treated area that grows, becomes firm or takes on a squared-off shape.

Fat freezing is also not a weight-loss treatment, and some people are better served by other approaches or no treatment at all. Our articles on non-surgical fat reduction and stubborn abdominal fat discuss realistic expectations.

Questions to ask at your consultation

• How would you recognize this reaction, and what would happen if I developed it?
• Are there reasons I might be at higher risk?
• What follow-up is planned after treatment, and for how long?
• Are there other options better suited to my goals?

Frequently asked questions

How soon would I notice it?

In this study, diagnosis came on average more than a year after treatment, and as early as about five months. The change is gradual, which is why follow-up visits and photographs help.

Does it go away by itself?

The study did not report cases resolving on their own. Liposuction corrected it in all six patients who chose surgery.

Is fat freezing still considered safe?

Most people tolerate it well, with temporary numbness, redness or tenderness being the usual side effects. This rare reaction is one of the risks that should be explained clearly before you decide.

If you are weighing body contouring options, HealthPark Medical Aesthetics can review your goals, explain the risks in plain terms, and help you decide whether any treatment is a good fit.

Source

Nikolis A, Enright KM. A multicenter evaluation of paradoxical adipose hyperplasia following cryolipolysis for fat reduction and body contouring: a review of 8658 cycles in 2114 patients. Aesthetic Surgery Journal, 2021. Read the study