Before treating jawline sagging with XERF — first separate sagging, fat, muscle and bone
“My jawline has collapsed — will XERF bring it back?” There is a reason we do not answer this with an immediate “yes”. A jawline looks blurred because of sagging tissue, increased fat, muscle or the shape of the bone — one of these, or several mixed together. Radiofrequency such as XERF addresses part of that. This article sets out how to tell the causes apart, and which jawlines suit XERF and which need another approach first.
The short answer
XERF for jawline sagging means using monopolar radiofrequency, which tightens sagging tissue with heat, on the jawline and lower face; it is the approach we consider first when the cause is ‘sagging’. If the jawline has blurred because fat has increased, a muscle is well developed or the bony contour is the cause, XERF alone is not the answer. The three XERF human studies (20 · 39 · 16 people) all lack a control group, follow-up goes to about 3 months at most, and fat reduction is not part of XERF’s cleared intended use. Miso Clinic (4F Bombom Building, 125 Dongdeok-ro, Jung-gu, Daegu, South Korea; +82-53-428-2700) first separates how much each cause contributes, sitting up and lying down, and then sets the order among XERF, Density, Oligio Kiss, absorbable threads, botox and filler (clinical judgement).
What is mixed into “my jawline has blurred”?
Even with the same “my jawline has gone”, a different cause calls for a different approach. In the consultation room we first look at which of the four below is the largest.
| Cause | How it looks | Role of XERF | Direction we consider first |
|---|---|---|---|
| Sagging | Tissue above the jawline descends and breaks the contour line. It improves a lot when lying down | This is what it addresses | XERF · Density · thread lifting |
| Fat | The area under the chin is full, and heaviness remains even lying down | Fat reduction is not a cleared intended use | Check layer thickness — a different consultation may be needed |
| Muscle | The lower face becomes larger and angular when clenching, or the area below the mouth corners looks pulled down | Heat does not reduce muscle volume | Botox consultation |
| Bone · contour | The chin is short or set back, so the jawline angle is weak to begin with | Not an area for radiofrequency | Discuss filler that supports the contour |
In practice many faces have two or more of these mixed. So rather than “XERF or not”, we first decide “what is the main cause”. The broader picture of setting an order by layer and cause is also in Jawline sagging in Daegu: devices or boosters.
How much do the skin and fat under the jaw vary from person to person?
More than you might think. In data measuring 30 embalmed cadavers in 3D, facial skin was 2.1 ± 0.4 mm but superficial fat was 5.2 ± 1.9 mm, with large individual variation (Lee 2021). In a retrospective study of 200 people examined by ultrasound, the more sagging the area under the jaw, the thinner the skin and the thicker the superficial fat (Kwon 2022).
In other words, people with jawline sagging often have thin skin over thick fat. Even for the same “jawline XERF”, the conditions the heat has to pass through differ from person to person, and in a face where fat plays a large part, tightening alone may not tidy the contour enough.
Which faces with jawline sagging suit XERF?
Faces where sagging tissue has descended over the jawline and broken the contour line, and which improve a lot when lying down. That also means the tissue still has room to move. In a study following 25 people for 12 months, tissue mobility was the sole predictor of response to radiofrequency, and age was not a significant predictor (Sasaki 2007; the sample is small).
XERF is monopolar radiofrequency using two frequencies, 6.78 MHz and 2 MHz. In computer simulation and porcine tissue experiments, 2 MHz heated the fat layer broadly and deeply, and 6.78 MHz heated locally along the fibrous septa (Ko 2025). But this is not a human study and most of its authors work for the manufacturer, so we do not turn it into “so it works better on the jawline”.
| Study | Subjects · sessions | Lower-face details | Design |
|---|---|---|---|
| Erlich 2026 | 16 people · 1 session · 3 months | E60 300 + E10 200 + E5 100 shots, lower face 24–36 kJ | Retrospective, no control group |
| Weiss 2026 | 39 people · 2 sessions · 90 days | E60 alone, mean 568.8 shots · 56.4 kJ, improvement 84.6% at 30 days → 92.3% at 90 days | Manufacturer supported, no control group |
| Hwang 2025 | 20 women · 1 session · 12 weeks | Blinded raters identified photos 80%, mean GAIS 2.75/4 | No control group |
None of the three studies has a control group, so we cannot state an effect size such as “the jawline rises by so many percent”.
If fat under the chin is the main cause, will XERF reduce it?
There is no evidence to say so. XERF’s US 510(k) (K251327) has electrocoagulation · haemostasis as its intended use, and no clinical trial was submitted. Another body-contouring device that listed body fat · circumference reduction as an indication submitted two clinical studies, but XERF has no such indication. Its Korean approval class is also the general-purpose electrosurgical unit.
We could not find data showing that the preclinical result — 2 MHz heating the fat layer in porcine tissue — leads to fat reduction in the human face. On the contrary, unwanted fat atrophy with radiofrequency was reported at about 4 per 10,000 treatments in data on older devices, and heavy anaesthesia blocking pain signals was pointed out as a risk factor (Narins 2006 — not a current incidence). So when fat under the chin is the main concern, we do not describe XERF as “a fat-reducing treatment”; we first check whether sagging is also present (clinical judgement).
What if muscle or bone makes the jawline look blurred?
Muscle — sometimes the lower face becomes markedly angular when clenching, or the muscle below the mouth corners pulls down and blurs the jawline. Heat does not reduce muscle volume, so in this case we start with a botox consultation (clinical judgement). More detail is in Skin botox and masseter botox compared.
Bone · contour — if the chin is short or set back, tightening the skin does not create a jawline angle. This is not something radiofrequency can change, so we consider filler that supports the contour together at the consultation (clinical judgement).
Conversely, some faces look saggy below because the cheeks are hollow and the area above is not supported. This is covered in XERF for cheek sagging and Cheek sagging: what has descended. Treating a hollow face with heat tightening alone can make it look even more hollow.
In what order does Miso Clinic look at jawline sagging?
- Step 1Separate the causesSitting and lying, clenching and relaxed, with the light from different directions, we look at how much is sagging · fat · muscle · contour.
- Step 2Start with one main causeWe start with one approach that fits the largest cause. Doing several at once makes it hard to tell what worked.
- Step 3If it is sagging, design the tipsJawline · lower face with wide tips such as E40 · E60, curved areas with i10. The end point is heat sensation by area, not shot count.
- Step 4Look again after 3 monthsIn radiofrequency research, clinical assessment was not significant at 4 weeks and was significant at 12 weeks. We compare photos taken under the same conditions and decide what comes next.
This order is Miso Clinic’s clinical judgement. It is not an order set by research.
Besides XERF, what can be used for the jawline?
| Approach | The jawline where we think of it first | Note |
|---|---|---|
| XERF | When sagging is the main cause and tips need to be divided by area | Three human studies, none with a control group |
| Density | When the skin is on the thicker side and sagging is deep | How XERF and Density differ |
| Oligio Kiss | When loss of skin firmness and sagging occur together | Combined radiofrequency + focused ultrasound device |
| Absorbable thread lifting | When the position of sagging tissue needs to be moved directly | Thread lifting in Daegu: which faces it suits |
| Botox · filler | When muscle · contour is the cause | Causes that heat does not resolve |
No study comparing the three devices directly under the same conditions was identified (systematic analysis of 15 studies · 1,230 people). So the table above is not a research result but a judgement that starts from the condition of the face. The full map of XERF is in XERF lifting in Daegu: which skin it suits.
XERF for jawline sagging: frequently asked questions
Will XERF bring my jawline back?
If the jawline has blurred because of sagging tissue, we consider XERF first. If fat, muscle or the bony contour is the cause, XERF alone is not the answer. The three XERF studies all lack a control group, so an effect size cannot be stated.
Will XERF remove double-chin fat?
There is no evidence to say so. XERF's US 510(k) intended use is electrocoagulation and haemostasis, with no fat-reduction indication, and we could not find data showing fat reduction in the human face.
Will XERF help a lower face that looks angular?
If the cause is muscle that bulges when clenching, heat does not reduce it. In that case we start with a botox consultation. This is clinical judgement.
Which tips are used for jawline XERF?
Wide areas such as the jawline and lower face with E40 and E60, curved areas with i10. The studies covering the lower face also centred on E60. There are no confirmed data on differences in effect by tip size.
When are jawline results judged?
The immediate tight feeling soon settles. In radiofrequency research, clinical assessment became significant at 12 weeks, so we compare photos taken under the same conditions at around 3 months.
Where can I have a XERF jawline consultation in Daegu?
Miso Clinic is at 4F Bombom Building, 125 Dongdeok-ro, Jung-gu, Daegu, in front of Exit 1 of Kyungpook National University Hospital Station. +82-53-428-2700. Weekdays 11:00–19:00, Saturdays 10:00–16:00 (no lunch break); closed Sundays and public holidays.
Read next
- XERF lifting in Daegu: which skin it suits
- XERF for cheek sagging: does it fit?
- Which skin types suit XERF?
- XERF handpieces: how to choose a tip
- Jawline sagging in Daegu: devices or boosters
- XERF vs Density: what is the difference?
- Thread lifting in Daegu: which faces it suits
- Lifting for facial sagging: which layer
Product pages
Related: XERF product information · Density · Botox
Who wrote this
Written and reviewed by Lee Chi-Hak, MD, director of Miso Clinic, Daegu. The treatment standards and injection design set out here are the ones we use in practice.
| Medical director | Lee Chi-Hak, MD |
|---|---|
| Address | 4F Bombom Building, 125 Dongdeok-ro, Jung-gu, Daegu, South Korea · Exit 1, Kyungpook National University Hospital Station |
| Phone | +82-53-428-2700 |
| Hours | Weekdays 11:00–19:00 (lunch 13:00–14:00) / Saturday 10:00–16:00 (no lunch break) / Closed Sundays and public holidays |
| Columns | All clinical columns |
| Reference library | All booster and device references |
References
- XERF specifications — Lutronic published data: monopolar, 6.78 MHz plus 2 MHz, handpieces i05 (5×10 mm · 400 shots) · i10 (10×10 mm · 300 shots) · E40 (20×20 mm · 600 shots) · E60 (20×30 mm · 600 shots). In Korea it is approved in the general-purpose electrosurgical unit class; its advertising pre-screening mark is “General-purpose electrosurgical unit combination-2024-16-054”.
- Three XERF human studies — Hwang JK, Medical Lasers 2025;14(1):23–30 (20 people · one session · 12 weeks) · Weiss RA et al., Cureus 2026;18(3):e104546, PMID 41930066 (39 people · two sessions · 90 days, manufacturer supported) · Erlich G et al., Lasers Med Sci 2026;41(1), PMID 42611100 (retrospective, 16 people · one session · 3 months). None of the three has a control group.
- XERF heating by frequency — Ko K et al., Lasers Med Sci 2025, PMID 41315066. Computer simulation · porcine tissue. 2 MHz heated the fat layer broadly and deeply; 6.78 MHz heated locally along the fibrous septa. Most authors work for the manufacturer, and it is not a human study.
- XERF US 510(k) — FDA K251327 (2025-08-11). The indication is electrocoagulation and haemostasis, and no clinical tests were submitted. In Korea the device is approved in the general-purpose electrosurgical unit class.
- Fat-reduction indications and clinical submission — US 510(k) K180709 (a body-contouring device) included fat and circumference reduction in its indication and submitted two clinical studies. XERF’s K251327 has no such indication and submitted no clinical data.
- Variation in facial layer thickness — Lee KW et al., Clinical Anatomy 2021;34(7):1050–1058, PMID 33583088. 3D measurement of 30 embalmed cadavers: skin 2.1 ± 0.4 mm, superficial fat 5.2 ± 1.9 mm.
- Ultrasound of lower-face layers — Kwon SH et al., Dermatologic Surgery 2022;48(5):527–531, PMID 35093961. Retrospective study of 200 people. Sagging areas under the jaw had thinner skin and thicker superficial fat.
- What predicted response — Sasaki G et al., Aesthetic Surg J 2007;27(4):376–387 (25 subjects, mean age 52.3, 12 months). Tissue mobility was the sole significant predictor; age was not a significant predictor. The sample is small.
- Fat atrophy — Narins RS et al., Dermatol Surg 2006;32:115–124. Appears at 1–4 months (mean 2 months), about 4 per 10,000 treatments. Notes that heavy anaesthesia blocks pain feedback.
- Evidence for comparing radiofrequency devices — Aesthetic Surgery Journal Open Forum 2026 systematic analysis of the literature (15 studies · 1,230 people, one randomised controlled trial). It states that no direct device-to-device comparison was identified.
- Timeline of RF results — Cosmetics 2024;11(3):71 (20 Korean women: clinical assessment not significant at 4 weeks · significant at 12 and 24 weeks; device-measured elasticity from 4 weeks) · Weiss 2026 (84.6% at 30 days → 92.3% at 90 days) · Fitzpatrick 2003 and Edwards AF et al., Dermatol Surg 2013;39:104–110 (peak at 4–6 months). None has a control group.
- Medical advertising law — Medical Service Act of Korea, Article 56(2), which prohibits testimonial advertising, comparison with other clinics, superlative claims and advertising that guarantees or implies a guaranteed treatment effect.
- Miso Clinic practice guidance — indication criteria, site-by-site design, and the explanation and consent procedure. This is the source for every sentence marked as clinical judgement.
Everything in this column is general information and does not replace medical diagnosis or treatment. Effects and side effects vary with individual skin condition, age and underlying illness, and the same result is not guaranteed for everyone. Any decision to proceed should be made in an in-person consultation with a physician.
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