Fat-Dissolving Injections (Mesofat): What They Are and Where

A fat-dissolving injection, or mesofat, is the injection of a substance into a specific subcutaneous fat layer so that the active ingredient breaks down the walls of the fat cells in that area until they dissolve, after which the body gradually clears them away. The aim is to address localized fat pockets, such as under the chin, a double chin, or the cheeks. It is not a method for whole-body weight loss. Results vary by individual.

What Is a Fat-Dissolving Injection (Mesofat)?

Mesofat is a general term for injecting a fat-dissolving substance into the subcutaneous fat layer at a specific spot. The substance in this group with the most supporting research is deoxycholic acid (DCA), a bile acid that occurs naturally in the body and helps digest and absorb dietary fat. When synthesized and injected into a specific fat layer, it acts to break down the walls of the fat cells in the injected area.

Abroad, deoxycholic acid under the trade name Kybella (ATX-101) was approved by the U.S. Food and Drug Administration (FDA) in 2015 to reduce moderate to severe submental fat (fat under the chin) in adults. It is considered the first injectable approved for this purpose.

A key point to understand is that fat-dissolving injections address fat “locally” in pockets that resist exercise or dieting. They are not a tool for whole-body weight loss. People who want to lose overall weight still need to rely on diet control and exercise as the foundation. This method is therefore most appropriate for people whose weight is already fairly stable but who still have localized fat deposits they want to reshape, and it should always follow an assessment by an experienced doctor.

How Does a Fat-Dissolving Injection Work?

The working principle of a fat-dissolving injection with deoxycholic acid is that, once injected into the subcutaneous fat layer, the substance disrupts and breaks down the fat-cell membrane (adipocyte membrane), causing the fat cells to rupture and die. The body then gradually clears the destroyed cells through its natural inflammatory and cleanup processes, which is the reason for the swelling in the early period after the injection.

Because the active ingredient is relatively specific to fat cells, the injection must be placed in the correct layer and position by a doctor, since injecting into the wrong layer or near important structures such as nerves may increase the risk of side effects. Study data indicate that the dose used in the under-chin area is about 2 milligrams per square centimeter, injected as individual points spaced about 1 centimeter apart, with each session spaced roughly 28 days apart.

The effect of this process therefore appears gradually and does not change immediately after the injection, because the body needs time to clear away the destroyed fat cells. It also usually requires several repeat sessions to see a clearer change. Results differ from person to person depending on the amount of fat, the location, and the body’s response.

Where Can Fat-Dissolving Injections Be Used?

The areas commonly chosen for fat-dissolving injections tend to be spots with pockets of fat that resist reduction by usual methods. The location with clear supporting data is under the chin or the double chin. Other areas, such as the cheeks, upper arms, or abdomen, are off-label uses (outside the main indication) offered by some clinics, so you should consult a doctor about suitability on a case-by-case basis.

What you should understand is that fat-dissolving injections work well for fat that forms clear pockets and is not too large in amount. If there is a large amount of accumulated fat or accompanying skin laxity, the doctor may recommend another method or a more suitable combined approach.

How Many Sessions Before You See Results?

In general, a fat-dissolving injection is not a single treatment that produces full results at once. Most cases require a course of several sessions, spaced about 4 weeks apart, to give the body time to clear the destroyed fat cells from each round. In studies of deoxycholic acid for the under-chin area, participants received up to 6 sessions, spaced no less than 1 month apart.

In terms of results, a 12-week double-blind, placebo-controlled study found that about 70% of those who received the active drug had at least a 1-grade improvement in their submental fat score, and about 13.4% improved by 2 grades, while the placebo group showed no change. These figures come from a study specific to the under-chin area, and results in each individual will naturally differ.

The appropriate number of sessions should therefore be assessed by an experienced doctor based on the area treated, the amount of fat, and the response after each injection, rather than being fixed identically for everyone. Results vary by individual.

How Long Do Fat-Dissolving Injections Last? Can the Fat Come Back?

Once the fat cells in the injected area are destroyed and cleared by the body, those fat cells are not regenerated in the same spot, so it can be said that the cells that were lost do not return. However, an important point to understand honestly is that the fat cells that remain in that area and throughout the body can still enlarge if your body weight increases.

So, even though the original cells do not return, if weight and lifestyle are not well managed, the fat in that area may appear to increase again as the remaining cells enlarge. Keeping the results lasting therefore depends on ongoing weight control, diet, and exercise. It is not something done once and then never maintained. Results vary by individual.

Side Effects of Fat-Dissolving Injections: How Many Days of Swelling?

The side effects most commonly seen after fat-dissolving injections are usually localized symptoms at the injection site, and most are temporary and mild to moderate. They include:

• Swelling, which is a common side effect, usually most noticeable in the first few days and possibly lasting about 1-2 weeks
• Tenderness or pain at the injection site
• Bruising, redness, or a feeling of warmth in the area
• A firm lump under the skin (induration) that may be temporarily palpable
• Numbness at the injection site, which usually improves gradually

In some people, swelling or firmness may last longer than a month. There are also less common but noteworthy side effects: in the under-chin area, the marginal mandibular nerve may sustain temporary injury, which studies found at about 2.1%, causing temporary asymmetry of the corner of the mouth or an uneven smile, as well as a small chance of a wound or tissue damage at the injection site in rare cases. If you have increasing pain, redness and warmth, fever, or other unusual symptoms, you should return to see the doctor promptly.

Who Should Not Have Fat-Dissolving Injections?

Fat-dissolving injections are not suitable for everyone. Groups who should avoid them or consult a doctor in detail beforehand include:

• People who are pregnant or breastfeeding, since there is not enough safety data to support it
• People with an infection in the area to be injected
• People who have had surgery under the chin or at the front of the neck, who have facial nerve problems, or who have difficulty swallowing, especially when injecting in the under-chin area
• People who expect to use it as a whole-body weight-loss method, which is not the purpose of the treatment
• People with underlying conditions or who are taking certain medications should inform the doctor for an assessment of suitability

A pre-treatment assessment by an experienced doctor is therefore very important, to consider whether the area you want to treat is suitable for this method and to reduce the risk of side effects.

Safety and Authenticity

The safety of fat-dissolving injections depends on several factors together: the product itself, the suitability of the person receiving the treatment, and the doctor’s technique. Data from clinical studies in large numbers of patients found that the side effects of deoxycholic acid are mostly localized and not severe, while serious complications are uncommon, though there is still a risk that must be managed appropriately.

For safety, you should choose a properly licensed medical facility, use a product that is registered and authorized by the Food and Drug Administration (Thai FDA), and have it done by an experienced doctor. You can ask the clinic for the product name, its origin, and to open the product in front of you. Choosing a clinic that provides transparent information and has a doctor overseeing the entire process is an approach that helps you feel more confident.

If you would like to care for your facial shape with another method as well, you can see the details of our fat-dissolving injection service.

References

• FDA approval label — Deoxycholic Acid (Kybella/ATX-101)
• Efficacy, safety, and potential industry bias in using deoxycholic acid for submental fat reduction — systematic review and meta-analysis (PMC)
• Uncommon Adverse Effects of Deoxycholic Acid Injection for Submental Fullness (PubMed)
• The Role of Fat Reducing Agents on Adipocyte Death and Adipose Tissue Inflammation (PMC)
• Deoxycholic acid (subcutaneous route) — Mayo Clinic
• Food and Drug Administration, Thailand (Thai FDA)

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This content is provided for general information only and is not a diagnosis or individual medical advice. Results vary by individual. Please consult a doctor for an assessment suited to you.