Meso Fat vs Masseter Botox: How to Slim the Face

How to slim your face: start by finding out why it looks wide

Which injection fits depends on whether the width comes from the jaw muscle, fat, bone or loose skin, because each is treated differently. [2][5]

An enlarged jaw muscle makes the angle of the jaw wider and the face look squarer. [5] Fat that builds up in one spot is another cause, and fat-dissolving injections have been reported for the cheeks, jawline and under the chin. [2]

The jaw bone is also worth having a doctor check. A 2025 review says that when the jaw muscle is enlarged, the bone at the angle of the jaw may change too, for example with a thicker outer layer of bone. [4]

This article shows which problem each option answers, so you can talk to your doctor about the right one. It does not replace an examination.

What can make a face look wide, and how a doctor checks

There are four causes a doctor should tell apart: jaw muscle, fat, bone and loose skin.

Jaw muscle: a 2025 review links an enlarged jaw muscle to teeth clenching, teeth grinding, heavy gum chewing and genetics. [4] Some studies grade it by feeling how much the muscle bulges when the teeth are clenched. [5]

Fat: a locally thick layer of fat under the skin is what fat-dissolving injections aim at. [2]

Bone: the same 2025 review says the bone at the angle of the jaw may change when the jaw muscle is enlarged. [4]

Loose skin: this means skin and tissue that has sagged, not extra muscle or fat. The review warns that when the jaw muscle shrinks quickly, the skin around the jaw may sag in some people, especially older people or those with thin skin. [4]

Meso fat vs masseter botox: how they differ

Meso fat (fat dissolving injections) targets fat, while masseter botox targets the jaw muscle, so they answer different causes. [2][5]

Meso fat. Targets: fat under the skin. [2] Suits: when the main problem is fat that has built up in one spot. [2] Good to know: the US FDA has approved only one fat-dissolving injection, and only for fat under the chin. [1]

Masseter botox. Targets: the jaw muscle, by relaxing it so it shrinks for a while. [4][5] Suits: a wide jaw caused mainly by an enlarged jaw muscle. [5] Good to know: the effect wears off, so the injection has to be repeated, and a 2023 review says no country has officially approved it for this use. [5]

Jaw bone and loose skin. Targets: neither method above. Botox acts on the nerve signals that reach a muscle, [5] and fat-dissolving injections target the fat layer. [2] Suits: when the main problem is bone or loose skin, which needs a different approach chosen by a doctor. Good to know: ask the doctor what that other option is and what risks it carries.

Meso fat on the face: the evidence and the risks

The evidence for fat-dissolving injections on the face is limited, and regulators in both the US and Thailand have warned about the risks. [1][2][3]

The US FDA says the only approved fat-dissolving injection is deoxycholic acid, for fat under the chin in adults, and that it is not approved for any other part of the body. Products sold online, which often contain phosphatidylcholine and sodium deoxycholate, have not been assessed by the FDA for safety or effectiveness. This FDA page was last updated on 20 December 2023. [1]

In Thailand, the Secretary-General of the Thai FDA (อย.) said on 7 June 2018 that the agency had never registered any fat-dissolving injection drug, and that only a doctor may give the injection. [3] That is a 2018 statement, so check the current status with the Thai FDA before you decide.

The evidence is not fully consistent. The Thai FDA said that year that no accepted medical research clearly shows these injections dissolve fat. [3] A retrospective study of 1,269 patients, with no control group, concluded that they reduce fat in the treated spot but are an add-on that cannot replace liposuction. [2]

Several risks are reported. That study found burning, swelling and redness were common, lumps under the skin in more than half of patients, and severe pain in 15 patients who were accidentally injected into muscle. [2] The US FDA lists permanent scarring, severe infection, skin deformities, cysts and deep painful hard lumps. [1] The Thai FDA lists severe allergic reaction, infection if the injection is not sterile, and wavy, uneven skin. [3]

What is masseter botox? Who it suits and its approval status

Masseter botox, also called jaw botox, is an injection of botulinum toxin into the jaw muscle that makes the muscle relax and shrink for a while. [4][5] It suits people whose wide jaw comes mainly from an enlarged jaw muscle, as judged by a doctor. [4][5]

A 2025 review says botulinum toxin type A injection is the standard non-surgical treatment for an enlarged jaw muscle, but experts have not agreed on the amount to use. [4]

The effect of botox wears off gradually, so it has to be repeated to keep the shape. [5]

On approval status: the US label of one cosmetic botulinum toxin type A product (indications revised 10/2024) lists frown lines between the eyebrows, crow’s feet, forehead lines and neck muscle bands. Jaw slimming is not on the list. [6] A 2023 review says no country has officially approved botox for jaw reduction. [5] This does not tell you the status of any product sold in this shop.

The same label lists the contraindications as allergy to the toxin or any of its ingredients, and infection at the injection site. [6]

What are the risks of masseter botox?

Most reported side effects are mild and temporary, but a few are worth knowing before you decide. [5]

The most common are weaker chewing for a while, pain where it was injected, headache and a hollow look in the middle of the cheek. [5]

If the toxin spreads to nearby muscles, it can change your smile or make your expression look unnatural. [4][5]

After the muscle shrinks quickly, the skin and tissue around the jaw may sag. This is uncommon, but more likely in older people or those with thin skin, and some people have reported an abnormal muscle bulge. [4]

The US label also warns of serious adverse reactions from using the toxin outside its approved uses, and of toxin effects that may spread far from the injection site. Get medical help right away if you have trouble swallowing, speaking or breathing. [6]

What to ask your doctor before you decide

First ask what is making your face wide, then ask whether the product and method on offer target that cause.

“Face slimming injection” is a broad name. It does not say which drug is used or which layer it goes into, so ask for the drug name, the area and the depth every time. The Thai FDA has warned that steroids have been used off-label in fat-dissolving injections, which may cause dents in the skin, infection or fluid swelling. [3]

If your jaw is enlarged from clenching or grinding your teeth, the doctor may also consider other approaches, such as a night-time bite splint, physical therapy and changing habits. [4]

The injection must be given by a licensed doctor. Never buy the product and inject it yourself: the US FDA warns of the risks of self-injecting products bought online, [1] and the Thai FDA says only a doctor may give fat-dissolving injections. [3]

• Is my wide face from muscle, fat, bone or loose skin, and how do you tell? [4][5]
• What is the name of the drug you will inject? Can I see the label and the Thai registration documents? [3]
• If we choose masseter botox: what are the risks to my smile, chewing and skin sagging, and is there a plan if they happen? [4][5]
• If we choose meso fat: is this drug registered or approved for this area? [1][3]
• If something feels wrong after the injection, who do I contact and what should I do?