— Why Do Double Chins Occur: 3 Anatomical Causes - Fat, Skin Laxity, and Muscle
A double chin doesn't arise from a single cause. Even double chins that appear similar externally can be broadly categorized into three main causes: adipose type, skin laxity type, and digastric muscle hypertrophy type. These three involve different anatomical layers, and their treatment approaches vary significantly. Choosing a procedure without accurately classifying the cause makes it difficult to achieve the desired results.
Understanding the anatomical structure of the lower jaw is the starting point for treatment. The layers beneath the chin are composed, in order, of the epidermis, dermis, subcutaneous fat layer, SMAS (Superficial Musculoaponeurotic System), digastric muscle and mylohyoid muscle, and the deep fat layer. If excessive subcutaneous fat accumulation is the cause, a fat reduction approach is effective. If decreased elasticity of the skin and SMAS layer is the cause, a lifting approach is effective. If muscle hypertrophy is the cause, a Botox approach is effective.
1. Fat-Type Double Chin — Characteristics of Submental Fat and the Scientific Mechanism of Lipolytic Injections
Fat-type double chin is a condition where the subcutaneous fat layer (submental fat) under the chin is excessively developed. It can occur genetically, regardless of body type, even in younger individuals. The fat cells in this area have a characteristic of not easily reducing even with weight loss, making it often difficult to resolve through diet and exercise.
▶ Mechanism of Action of Lipolytic Injections
Lipolytic injections are agents that selectively dissolve fat cell membranes, with deoxycholic acid (DCA) as the main component. In 2015, the US FDA first approved a deoxycholic acid formulation (Kybella) for reducing submental fat, and since then, various equivalent formulations have been used worldwide. Deoxycholic acid, a component of bile acids, directly destroys the phospholipid bilayer of fat cell membranes, selectively causing cell death. The dead fat cells are phagocytosed and eliminated by macrophages. This process also stimulates collagen in the surrounding connective tissues.
▶ Clinical Characteristics
Inflammation and fat decomposition occur over 2-4 weeks post-procedure, with results becoming clearly visible after 6-8 weeks. A significant reduction in fat volume can be achieved with just one treatment, and repeat treatments can be performed every 2-4 weeks as needed. Fat cells destroyed by deoxycholic acid do not regenerate permanently, allowing for long-term maintenance of results. Common side effects may include swelling, bruising, and numbness for several days after the procedure, which are expected treatment responses and resolve naturally.
2. Skin Laxity-Type Double Chin — A Strategy to Rebuild the SMAS Layer with HIFU and Radiofrequency Lifting
With aging, dermal collagen decreases, the SMAS (Superficial Musculoaponeurotic System) loosens, and supporting ligaments weaken. This causes the skin under the chin to sag downwards, forming a double chin. In such cases, lifting treatments that restore elasticity to the skin and deep tissues are key, rather than fat reduction approaches.
▶ Ultraformer III (HIFU): Lifting Through Deep Tissue Coagulation
High-Intensity Focused Ultrasound (HIFU) passes ultrasound energy through the skin surface and concentrates it on target tissues at specific depths. Ultraformer III uses cartridges at 4.5mm (SMAS layer), 3.0mm (deep dermis), and 1.5mm (dermis) to induce selective thermal coagulation zones (TCZ) layer by layer. In the TCZ, heat of approximately 65-70°C is generated instantaneously, causing collagen denaturation. Subsequently, new collagen synthesis is promoted during the wound repair process. Concentrating HIFU energy on the submental area leads to immediate contraction of the SMAS layer and long-term collagen regeneration, improving skin sagging.
▶ Innoface Lifting (RF): Selective Radiofrequency Heating within the Dermis
Innoface utilizes bipolar radiofrequency (RF) to target dermal collagen. RF energy is absorbed intensively by the water-rich dermal layer according to skin impedance, generating thermal energy. This heat induces immediate collagen contraction and sustained new collagen formation, improving skin elasticity and lifting the sagging skin under the chin.
▶ HIFU vs. RF: Selection Criteria for Skin Laxity-Type Double Chin
- Depth of Sagging: For cases where SMAS laxity is primary, HIFU (4.5mm cartridge) is advantageous. For cases where reduced dermal elasticity is primary, RF is effective.
- Skin Thickness: HIFU's deep penetration is advantageous for thicker skin, while RF's surface energy may be more suitable for thinner skin.
- Combination Therapy: Combining both methods can be expected to yield synergistic effects across different layers.
3. Digastric Muscle Hypertrophy-Type Double Chin — The Role of Submental Muscles and Botox Treatment
Although a relatively less common cause, in some individuals, hypertrophy of the anterior belly of the digastric muscle can create an appearance resembling a double chin. The digastric muscle is a muscle connecting the mandible (jawbone) to the hyoid bone, functioning when opening the mouth or chewing. If this muscle is enlarged, it can create volume under the chin, making it look like a double chin even without excess fat. Diagnosis can be made by observing muscle contraction when the mouth is open or through palpation.
In such cases, treatment involves injecting a small amount of botulinum toxin into the anterior belly of the digastric muscle to reduce muscle volume. However, this procedure requires advanced anatomical knowledge, and precise control of the injection site and dosage is essential to avoid affecting adjacent muscles involved in swallowing and speech.
4. Integrated Treatment Strategy for Combined-Type Double Chin — Layered Approach Based on Cause
In clinical practice, double chins are most commonly a combination of fat and skin laxity rather than a single cause. This is particularly true for individuals over 30-40 years old, where fat reduction alone may not yield satisfactory results. In such cases, a layered approach as follows is recommended:
Step 1 — Fat Reduction (Lipolytic Injections): First, reduce submental fat volume to refine the overall contour. It is important to anticipate that skin laxity may become more apparent after fat reduction and plan the treatment accordingly.
Step 2 — Lifting (Ultraformer III or Innoface Lifting): After fat reduction, lift the sagging skin to create a clean jawline. It is generally recommended to perform lifting procedures after a minimum recovery period of 4-8 weeks following fat reduction treatments.
Step 3 — Maintenance: Repeat lifting procedures every 6-12 months to maintain results. If fat re-accumulation occurs due to weight gain, additional lipolytic injections may be administered.
5. Double Chin Procedures: Which Treatment is Right for Me? — Diagnostic Checklist
The checklist below can help you gauge your double chin type.
- Feels soft and fatty when touched → Fat type / Lipolytic injection is the primary choice.
- Chin fat doesn't easily reduce even with weight loss → Genetic fat over-accumulation / Suitable for lipolytic injections.
- Didn't have it when young, but it appeared with age, and the skin feels loose → Skin laxity type / Ultraformer III or Innoface lifting is suitable.
- The area under the chin becomes more prominent when opening the mouth → Digastric muscle type / Consider Botox approach.
- Both fat and sagging skin are present (combined type) → Requires a phased, combined treatment plan.
Of course, an accurate diagnosis must be made through a direct consultation, and the above criteria are for reference only. Because treatment directions can vary significantly even for seemingly identical double chins, the diagnostic process of clearly identifying the structural cause before the procedure is most crucial.
6. BA Clinic's Approach to Double Chin Treatment
At BA Clinic, we prioritize classifying the anatomical cause before treating a double chin. We comprehensively evaluate the thickness and distribution of the fat layer, the state of skin elasticity, and the muscle structure, then design the most suitable method or combination of lipolytic injections, Ultraformer III, and Innoface lifting. We aim not just to recommend a single procedure but to achieve a natural and balanced jawline through accurate treatment for each cause.
If you have any questions about double chin improvement, please feel free to request a consultation at BA Clinic.
