Mewing megathread — science, technique, results

Mewing has become one of the most discussed topics in this community and also one of the most misunderstood. Let me lay out what the science actually says, what the technique is, and what realistic results look like.

Mewing is a term coined from the work of Dr John Mew and his son Dr Mike Mew, British orthodontists who have been advocating for orthotropics — the idea that craniofacial development is heavily influenced by oral posture and function. The core claim is that resting your tongue on the roof of your mouth (the palate) rather than letting it rest on the floor of the mouth or behind the teeth influences jaw and facial development over time.

The science: craniofacial bones, like all bones, are subject to Wolff's Law — they remodel in response to the mechanical forces applied to them. The evidence that oral posture affects facial development in children and adolescents is solid. Growing skulls respond to functional forces. The question for adults is whether adult craniofacial bones can still remodel to any meaningful degree under these forces. The honest answer is that the peer-reviewed evidence for adult results is weak. There are case reports and before/afters but no good RCTs.

However — and this is important — there are documented adjacent benefits: improved airway, reduced mouth breathing, better posture of the neck and cervical spine, reduced TMJ issues in some people. These benefits are real regardless of whether the jaw widens.

The technique: full tongue suction hold on the palate. Not just the tip of the tongue — the whole tongue surface should press up against the palate. Lips lightly sealed. Teeth slightly touching or lightly together. This is how your tongue should rest all the time — not just when you're consciously doing it. Nasal breathing is the prerequisite; you can't mew properly if you're a chronic mouth breather.

If you're a minor, the evidence for meaningful structural change is much stronger. If you're over 25, don't quit your job to mew — but doing it correctly costs nothing and the posture/airway benefits are worth it.

This is the framing I try to give people when they ask about mewing. The orthotropics argument makes sense within the framework of Wolff's Law and functional forces on bone — the problem is the adult evidence is mostly anecdotal. That said, the posture correction component alone is worth the practice. A lot of people in this community have forward head posture from years of screens which pulls the mandible down and back. Correcting that changes your face substantially without any bone remodelling.

Do you think the chewing component (mastic gum, Falim gum) has better evidence than resting tongue posture for jaw development in adults? I've seen claims that masseter hypertrophy from chewing gives a better jawline but I'm not sure how much it actually matters vs reducing body fat.

Masseter hypertrophy from consistent hard chewing is well-documented and observable — you can see the muscle develop similarly to any other skeletal muscle. Whether that improves your jawline aesthetically depends on your existing jaw shape. For some people wider masseters create a squarer jaw that reads as more attractive. For others it creates a boxy look that detracts from mid-face harmony. It's not universally positive. Getting to a lower body fat percentage will almost always do more for jaw definition than masseter development.

How long before you start noticing the tongue posture becoming natural and not requiring conscious effort? I keep forgetting and then realising my tongue is just resting at the bottom of my mouth.

For most people it takes 3-6 months of consistent practice to start defaulting to correct posture. The difficulty is that you can't practise while sleeping, and many mouth breathers do most of their airway dysfunction at night. If you suspect you're a habitual mouth breather — especially at night — it's worth looking into nasal breathing exercises and potentially seeing an ENT if there's structural obstruction (deviated septum, hypertrophic turbinates) preventing comfortable nasal breathing.