What the research shows
Deoxycholic acid injections (sold as Kybella) dissolve fat cells. In the large North American trials, about two in three treated patients improved by at least one grade, against about one in five given placebo injections, and most improved within two to four sessions spaced a month apart (Jones 2016, Dayan 2018). Among patients who responded, the result held for three years in most, without more injections (Humphrey 2021).
Side effects are common and short-lived. Swelling, pain, numbness and firmness at the injection site usually settle before the next session (Cunha 2021, Inocêncio 2023). Temporary weakness of the lower lip, from irritation of the nerve along the jaw, occurred in about 1 in 25 treated patients and went away on its own (Jones 2016). Rare reports after approval include skin loss needing hospital care in patients with other illnesses (Gibson 2024).
Fat freezing (cryolipolysis) shrinks the fat layer by a few millimeters. In the trial that led to FDA clearance for the chin, most patients were satisfied and no serious problems occurred (Kilmer 2016); pooled studies found a measurable drop in fat thickness and volume with mild, passing side effects (Do 2025).
Liposuction under local anesthesia is quick and safe. In a large series by dermatologic surgeons, temporary lip weakness occurred in a handful of patients and there was no skin loss or scarring (Habbema 2018). It helped older patients who could not have a facelift; a defined pocket of fat in the midline predicted a good result, and thin, crinkled skin predicted failure (Gryskiewicz 2003).
Many full necks are not mainly fat. Loose platysma muscle, fat below the muscle, large salivary glands and loose skin do not improve with fat removal alone, so surgeons examine for each before choosing a treatment (Fattahi 2012, Marten 2018).
Where surgeons disagree
- Injections or liposuction. No trial has compared them directly. At the doses used in the trials, a full injection course cost about $6,400 against about $3,000 for liposuction in a survey of facial plastic surgeons (Patel 2018).
- How safe liposuction is. A large single series reports very few problems (Habbema 2018); a review of published reports counted more, mostly minor: fluid collections, surface irregularities and visible neck cords (Girão 2026).
What is new
- Necks treated with injections, freezing, radiofrequency devices or threads before a neck lift showed scarring and lost fat at surgery, which made the operation longer and the result less smooth (O'Daniel 2026). A patient who may want a neck lift later can weigh this first.
- New injectable fat reducers are in trials, including a deoxycholic acid product in China and a single-session drug that reduced fat on MRI (Ting 2025, Shridharani 2023).
What is still unknown
- How independent the injection evidence is: all of the main trials had industry ties (Inocêncio 2023).
- How freezing and energy devices compare with injections or surgery: the device studies are small and lack control groups (Do 2025).
Key papers
- Gryskiewicz 2003: which patients do well with chin liposuction alone.
- Fattahi 2012: why most full necks need more than liposuction.
- Jones 2016: the pivotal deoxycholic acid trial, with the lip weakness rate.
- Kilmer 2016: the fat freezing trial that led to FDA clearance for the chin.
- Patel 2018: cost of injections against liposuction.
- Marten 2018: how surgeons diagnose the parts of a full neck.
- Humphrey 2021: injection results hold for three years.
- Cunha 2021: pooled trials; the lower dose works as well as the higher one.
- O'Daniel 2026: nonsurgical neck treatments make a later neck lift harder.