Cryotherapy and fat freezing are not two versions of the same idea. The word "cryo" does a lot of work in making them look alike. Whole-body cryotherapy puts you in a chamber or booth of very cold air or nitrogen vapour. It lasts two to three minutes. Localised cryotherapy points cold air at one area for a few minutes. CoolSculpting is different. It places a cooled cup on a single bulge, draws the tissue into it, and holds it at a set temperature for 35 to 60 minutes.
On whole-body cryotherapy the FDA has said something unusually plain, and it is worth quoting properly. The agency published a Consumer Update on 5 July 2016. It was titled "Whole Body Cryotherapy (WBC): A 'Cool' Trend that Lacks Evidence, Poses Risks". In it the agency stated that "not a single WBC device has been cleared or approved by the agency in support of these claims". An FDA medical officer was asked whether the agency had found whole-body cryotherapy safe and effective. The answer was: "That is not the case." The same update said FDA "found very little evidence about its safety or effectiveness in treating the conditions for which it is being promoted". Weight loss was one of the claims the agency named as promoted and unsupported.
The physics of the comparison is not subtle. Cryolipolysis is a dose. It is a set temperature held for a set time, with the skin in contact with a cooled applicator. The founding animal work used 10 minutes at between minus 1 and minus 7 degrees Celsius. That was enough to inflame the fat lobules. The cleared human settings are minus 10 degrees for 60 minutes under the chin, and minus 11 degrees for 35 minutes on the upper arm. Two to three minutes of cold air over the whole body does not deliver that mix of temperature and time to the fat under the skin. That reasoning follows from the published settings. No study has tested it head to head, because nobody has proposed the chamber as a fat treatment in the literature.
CoolSculpting's claim, by contrast, is narrow, named and cleared. Its device category was created by a De Novo authorisation, DEN090002, decided 24 August 2010. Each body area since has been added by a separate 510(k). A 510(k) is a finding that a device is much the same as one already on sale. It is not a finding that the device works.
It is sold for recovery, soreness, inflammation and general wellness. In many places it is also sold for slimming.
One area, one bulge, one timed cycle.
It sets off a whole-body response. Blood vessels narrow, then widen, and markers in the blood shift. It is not built to bring the fat under the skin down to a temperature that kills fat cells. No measurement showing that it does has been published.
Fat crystallises and inflames at temperatures the nearby skin, nerve and muscle can take. The cells die over days. The body clears them over months.
That is the agency's own wording about whole-body cryotherapy devices. It is a statement about clearance. It is not a finding that the chambers are useless for everything they are used for.
Under the chin and under the jawline are cleared separately, up to a body mass index of 46.2. CoolSculpting Elite is K212707, cleared 5 November 2021.
The cycle stops on its own if the surface temperature runs more than 1 degree past the target.
The published whole-body cryotherapy work sits in sports recovery, joint disease and inflammation. Work on obesity has measured whole-body and metabolic markers. It has not measured the thickness of a fat layer. None of it is evidence of fat reduction.
FDA pooled 4,792 cryolipolysis treatments. The mean fat-layer drop on ultrasound was 20.6%, or 3.9 mm, with study means from 10.3% to 25.5%. An independent randomised split-body trial measured about 14% at 12 weeks.
Whatever that is worth, it is not a contouring treatment. It has no cleared medical claim.
Not loose skin, not cellulite, not overall size.
FDA lists asphyxiation, above all where liquid nitrogen is used for cooling. It also lists low blood oxygen, loss of consciousness, frostbite, burns and eye injury. One teenager has been reported with reversible cerebral vasoconstriction syndrome, a spasm of the brain's arteries, set off by whole-body cryotherapy.
A review of 554 procedures called delayed pain starting a few days later not uncommon. It lasted 3 to 11 days. In one FDA-reviewed arm study, 4 of 30 patients still had numbness past 12 weeks.
One multi-site practice reviewed 18,203 cycles. The median was 4 cycles and 1 session per patient. The mean was 5.6 cycles.
The 2016 Consumer Update is worth reading closely rather than in summary. FDA said no whole-body cryotherapy device had been cleared or approved in support of the claims made for these chambers. It also said it found very little evidence about safety or effectiveness for the conditions they are promoted for. The promoted claims it named were weight loss, asthma, Alzheimer's disease, anxiety, chronic pain, depression and fibromyalgia. The list went on: insomnia, migraine, multiple sclerosis, osteoarthritis, rheumatoid arthritis, better circulation, metabolism and workout recovery.
What that statement is not is a ruling that cold does nothing: It is about the legal status of the devices, and about how thin the evidence is for the medical claims made for them. People who use cryotherapy for how it makes them feel after training are not making a medical claim. Nothing FDA said contradicts them.
What it is fatal to is the slimming claim: Weight loss was named outright as promoted and unsupported.
Damage aimed at fat depends on temperature and time together. Fat cells hold more lipid than the tissue around them. That makes them easier to injure with cold at temperatures skin and nerve can take. This is why the method is called selective cryolysis. The window is narrow at both ends. Too little cold and nothing happens to the fat. Too much and you injure the skin.
Every dataset in cryolipolysis comes from inside that window. Ten minutes at minus 1 to minus 7 degrees in the founding animal study. Sixty minutes at minus 10 degrees in the pivotal under-chin trial. Thirty-five minutes at minus 11 degrees for the upper arm. The applicator stays in contact with the skin over the target the whole time. The tissue is drawn into the cup, which cuts the blood flow that carries heat back in. The temperature is held to within half a degree.
A cryotherapy chamber does the opposite of all of that. The exposure is brief. It is to air, not to a cooled contact surface. It is spread across the whole body rather than aimed at one bulge. And it ends before deep tissue has changed temperature much. That is reasoning from the published settings, not the result of a head-to-head study, and it should be read that way. But no study has ever reported a thinner fat layer after whole-body cryotherapy, and that is the more important fact.
Sports recovery, muscle soreness, inflammation and joint disease. Most of that work uses the name whole-body cryostimulation. There is a real body of it, of mixed quality. Safety group reviews and a published list of reasons not to use it both exist.
Work touching obesity has looked at whole-body and metabolic effects. That means markers in the blood, and signalling molecules from fat tissue. It has not looked at the thickness of a fat layer at a treated site. Those studies are sometimes cited as if they showed fat reduction. They do not measure it.
For cryotherapy, FDA named weight loss as an unsupported promoted claim in 2016. It has not cleared any of the devices for medical treatment since.
For CoolSculpting, the same conclusion arrives from another direction. FDA's page for patients on non-invasive body contouring was last updated 15 October 2025. It states that these treatments "will not result in weight loss or contribute to the health benefits associated with weight loss". The maker's own safety information says the procedure is not a treatment for weight loss. A 2025 meta-analysis of cryolipolysis studies found no real change in weight. The figure was about 1.81 kg, with a confidence interval crossing zero and p = 0.09. The same dataset did report a change in body mass index.
The body mass index limit of 30 in the CoolSculpting indication is a ceiling on who can be treated. It is not a target the treatment aims at.
This risk belongs to cryolipolysis, not to the chamber. It is the main reason to treat an applicator session as a medical procedure rather than a spa appointment.
Paradoxical adipose hyperplasia is a firm, clearly edged, usually painless swelling of a treated area. The fat ends up bigger than it started. It usually shows up two to six months after treatment. It does not clear up on its own. Repeat cryolipolysis on the same area has been reported to make it grow further.
The published incidence estimates differ by about a hundredfold, largely because they count different things: The 2014 report that first described it gave 0.0051%, about 1 in 20,000 cycles. The maker's current safety information gives 0.01% to 0.1%. Eight Canadian centres reviewed 8,658 cycles and found 0.05% to 0.39% per cycle. A 2025 meta-analysis of 28 studies and 13,078 patients pooled it at 0.22%, roughly 1 in 455 patients, with a confidence interval of 0.10% to 0.47%. Its authors concluded the incidence "appears to be higher than manufacturer reports". They also noted that only 4 of the 28 studies followed patients out to 16 weeks or more. A 2025 review of 18,203 cycles at a single practice found 0.018% to 0.048% per cycle. StatPearls reports around 0.91%, about 1 in 110 treatments, and mentions recent estimates of up to 2%. Some of those figures are per cycle and some per patient.
Putting it right means an operation: In an 11-case series, 7 of the patients had surgery. Six had liposuction alone and 1 had liposuction with a tummy tuck. Three of those 7 needed a second procedure. Surgery is usually put off until the area softens, generally 6 to 9 months after the original treatment.
For a cryotherapy chamber, ask what is used for cooling and whether you are ever alone in the room: FDA's named hazards for whole-body cryotherapy start with asphyxiation, above all where liquid nitrogen is the coolant. They include low blood oxygen and loss of consciousness. Supervision and airflow are the things that matter.
For CoolSculpting, disclose cryoglobulinaemia, cold agglutinin disease or paroxysmal cold haemoglobinuria: These three rule the treatment out completely in the maker's safety information. In all three, cold destroys red blood cells.
Tell them in advance about a list of other things: Cold urticaria, Raynaud's disease, pernio or chilblains. Poor circulation or reduced feeling in the area. Nerve pain conditions, bleeding disorders or blood thinners. Recent surgery or scarring in the area. An implanted pacemaker or defibrillator. And any hernia in or next to the treatment site. Hernia in particular appears in FDA's class-level risk list, in the device's own precautions, and in the reported adverse events for this class.
Breathlessness, chest tightness, confusion or fainting during or right after a cryotherapy session, above all in a nitrogen-cooled chamber
Fever or chills after a treatment
Redness spreading outward from a treated area, visibly worse hour by hour
Pus or discharge from treated skin
White, waxy or hard skin that stays numb after rewarming, which can be frostbite
The first may be an asphyxiation or low-oxygen event. It needs emergency services. The rest need urgent care the same day.
A firm, well-defined lump appears in a CoolSculpting-treated area two to six months later, above all if it matches the shape of the applicator
Numbness in a treated area is still there beyond about three months
Pain is rising after the first few days rather than settling
Blistering, crusting or an open patch appears on treated skin
The skin over a treated area darkens a lot in the following weeks
An area starts to look dented or hollow next to the untreated side