Changes

CoolSculpting uses an FDA approved device to chill the skin for up to an hour<ref name="Avram-2009"/>, with a session lasting one to three hours<ref name="CSFaq"/>, producing a reduction in the fat thickness in the treated area. Animal and human studies have shown a reduction in fat thickness between 20% and 80% over 3 months following treatment<ref name="ClNelson"/>. The device sucks the skin and underlying fat into a cup<ref name="Coleman-2009"/>. More than one treatment can be used, but the results of the second treatment are not as dramatic as the first<ref name="Shek-2012"/>. CoolSculpting is considered an alternative to liposuction<ref name="StevensPietrzak2013"/>, which is the one of the most common types of plastic surgery<ref name="PlasticSurgry2013"/>. There are some initial indications that CoolSculpting may improve skin texture and laxity, with a tightening of the lose skin<ref name="CarruthersStevens2014"/>. While promising, more studies on skin laxity are needed.

=How does Does CoolSculpting workWork?=

CoolSculpting uses an approach of removing heat from the body at a constant rate, something they call Cooling Intensity Factor (CIF) <ref name="Bernstein2016"/><ref name="Zelickson-2009"/>. This makes it tricky to understand the actual temperatures involved, though studies often quote figures of around -5c to -10c for the temperature of the paddles that are in contact with the patient's skin. * A study looked at the temperature of the skin surface and the fat at a point 1.5cm below the surface during a 60 -minute CoolSculpting application set to -7c/19f<ref name="Sasaki-2014"/>. The skin surface dropped in temperature steadily during the 60 minutes until it was at an average of 12.3c/54f (+/-2.6c). The underlying fat temperature dropped for the first 30 minutes to around 13c/55f then cooled more slowly for the final 30 minutes to around 10c/50f. It's interesting to note that the skin temperature was warmer than the underlying fat, and that even though the CoolSculpting device was set to well below freezing point, the skin never got close to that cold. The CoolSculpting setting was a "Cooling Intensity Factor" of 42, and it's unclear to me how that relates to the actual temperaturewhich has units of mW/cm². * An animal study of two different machines that cooled showed a final skin temperature of 8.6c/47f and 5.8c/42f<ref name="JeongKwon2017"/>, which is similar to the human study. * Another study in 2017 evaluated two newer versions of the CoolSculpting device designed to go colder for a shorter period showed skin temperatures of -1.6c/29f and -7.1c/19f<ref name="Kilmer2017"/>. * Further research by ZELTIQ looked at how isolated pig fat cells responded to chilling for an hour and then rewarming<ref name="PreciadoAllison2008"/>. They found that chilling the fat cells to -2c, 0c or 2c caused the cells to die off (necrosis), while chilling them to 7f7c/45f caused some necrosis and some apoptosis (programmed cell death). Chilling the cells to 14c/57f, 21c/70f, or 28c/82f resulted in no necrotic injury and approximately the same apoptosis. Mouse * An early use of CoolSculpting used CIF of 42 mW/cm² and produced -10c, or CIF of 34 mW/cm² and produced -5c (both after 60 minutes.)<ref name="Bernstein2016"/>. * Isolated mouse fat cells exposed to 8c/46f for 10 minutes showed some crystallization, with more crystallization seen after 25 minutes<ref name="Pinto-"/>. The crystal structures were still visible after 2 hours at 22c/72f. * Colder temperatures have been investigated. Most studies compare to the standard CoolSculpting as -10c/14f for an hour. One small study of 15 subjects used -12c for 45 minutes and -15c for 30 minutes, deployed under the chin area<ref name="Leal SilvaCarmona Hernandez2017"/> (the fat reduction was less than 2mm). There's an abstract of a test using of 45 subjects using CIF of 50 mW/cm² (-15c/5f) for 45 minutes on the flanks, resulting in 4.2mm (+/-2.6mm, range 10.7mm to 0mm) <ref name="Kilmer-2015"/>.* According to the FDA fillings, a version of CoolSculpting branded as "CoolAdvanatage" uses -11c/12f for 45 or 35 minutes<ref name="FDA-CoolAdvantage-2017"/>.* Most images of patients after CoolSculpting show the fat has become semi-solid, which is sometimes referred to as the "butter stick". (Google for "CoolSculpting butter stick" for examples.) Some research from 1946 found that fat from 15 cadavers melted at various temperatures<ref name="Schmidt-Nielsen1946"/>. There was variation between individuals and between locations in the body. Subcutaneous abdominal fat melted around 31c-35c//88f-95f. * As another reference point, the most common fats in adipose (body fat) <ref name="Kunešová-2012"/> are Oleic acid (~45%) with a melting point of 13-14c/55-57f, Palmitic acid (~22%) with a melting point of 63c/145f, and Linoleic acid (~12%) with a melting point claimed to be from -16c/12f to -5c/23f (sources differ.) This means that Palmitic acid is always going to be solid and Linoleic acid is always going to be liquid, so the "butter stick" effect seems to come from Oleic acid. Any solidification would suggest the fat has been chilled below 13-14c/55-57f.All this research suggests that while relatively modest temperatures can result in the loss of fat cells, with CoolSculpting may use lower temperatures having and may have more impact.

A 2014 study showed an average of 7mm reduction in fat thickness two months after a single treatment (about 1.4oz/40g)<ref name="GaribyanSipprell2014"/>. A 2012 study of CoolSculpting showed an average reduction of about 4mm after two months<ref name="Shek-2012"/>. A second treatment had a lower reduction of an additional 1-2mm. Another study conducted between 2009 and 2012 of 518 patients showed an average of 23% reduction in fat thickness measured by calipers<ref name="DierickxMazer2013"/>. One patient showed a localized reduction of 2.2cm (nearly 1 inch) in fat thickness in spite of an increase of 0.1 Kg in overall weight. Note that the FDA clearance for CoolScuplting specifies a BMI of <=30 kg/m²<ref name="FDA-CoolSculpting-2017"/>.

A common concern is frostbite, or other damage to the skin. This should not be a problem if correctly performed, as you need far colder temperatures (-10c/14f) to cause that type of damage<ref name="Gage-1982"/><ref name="Gage-1979"/>. A study of mice showed the minimum time and temperature for cell damage is -4c/25f for 3 min<ref name="BournePiepkorn1986"/>, but this is actual cell temperature, not exposure to that temperature. CoolSculpting uses temperatures that do not immediately kill off the fat cells, but rather trigger the natural process of cell death ([http://en.wikipedia.org/wiki/Apoptosis apoptosis]). That's why CoolSculpting takes weeks or months for the full effect to be seen. (* There is one case report of frostbite from commercial Cryolipolysis received at a beauty salon<ref name="ChoongWohlgemut2017"/>, but it's not clear if this was an official ZELTIQ CoolSculpting treatment or not.* There are reports of occasional frostbite in patients using a machine to pump ice/water to improve post-operative recovery<ref name="McGuireHendricks2006"/>. These incidents are rare, with only 4 patients out of thousands having an issue, and the site of the frostbite is over the patella (kneecap)where blood supply may be a little more limited. * While there are reports of frostbite from gel packs<ref name="RivlinKing2014"/>, this appears to be surprisingly rare given the sales of gel packs. * A comparison of ice and gel packs showed that after 20 minutes ice reduced skin temperature to 10c/50f and gel packs to 13.6c/56f<ref name="Kanlayanaphotporn-2005"/>. Another study using different amounts of ice showed that larger quantities of ice produced colder skin temperatures, with 0.6Kg/1lb producing an average of 6c/43f and a minimum of 4.4c/40f<ref name="Janwantanakul2009"/>.

* A common side effect is that the skin being treated goes red, with some bruising and numbness<ref name="ClNelson"/>. I suspect that the bruising may be because the CoolSculpting device sucksthe fat against the cooling device<ref name="Coleman-2009"/> the fat against the cooling device. These problems normally resolve within a week. The numbness is not associated with nerve damage<ref name="Coleman-2009"/>.* While most patients find CoolSculpting uncomfortable, some suffer from "delayed onset pain." A study of 125 patients who underwent 554 treatments found 19 (15%) suffered from this problem<ref name="KeaneyGudas2015"/>. The criteria for defining delayed onset pain was two of stabbing/shooting/burning pain, pain that disrupted sleep, or pain unresponsive to pain medication. The pain lasts 3-11 days, with no permanent symptoms.

=How long does it take Long Does It Take to workWork?=

CoolSculpting is quite different to Cryosurgery, which uses cold to kill off tissue, such as tumors. Typically , cryosurgery uses far lower temperatures (-20c/-4f to -40c/-40f) and immediately kills off the living cells ([http://en.wikipedia.org/wiki/Necrosis necrosis]) <ref name="CryosurgeryTemp"/>. Cell damage is caused by temperatures below -10c/14f<ref name="Gage-1982"/><ref name="Gage-1979"/> and CoolSculpting does not go that cold.

* Never use any type of gel pack. These start too cold and can easily cause frostbite<ref name="Stevens-1978"/>, and they warm up too quickly<ref name="ChestertonFoster2002"/><ref name="Kanlayanaphotporn-2005"/>.

I've made a number of tests, monitoring my skin temperature for up to three hours. The graph below shows three tests where I took temperature readings every 15 minutes, and it's fairly typical of what I see. The skin temperature initially drops fairly quickly, dropping to around 5-15c/40-60f within five minutes, and stabilizing around 5-10c/40-50f within 15-20 minutes. After that, the temperature tends to be reasonably stable, and most of the variation is down to how much the ice water is moved. If the bag of ice water is kept very still, the skin temperature will rise somewhat, but if it's actively agitated, then the skin temperature can drop. It takes some effort for me to get the skin temperature below 2c/36f, and obviously, the skin temperature never drops below freezing, as the ice water isn't that cold. This is broadly similar to research studies<ref name="Kanlayanaphotporn-2005"/><ref name="BelitskyOdam1987"/><ref name="Janwantanakul2009"/>.