Mewing

Mewing is the practice of resting the tongue flat against the roof of the mouth, with the lips closed and the teeth lightly together, named after the orthodontists John and Mike Mew. The claim attached to it online is that sustained tongue posture remodels the adult jaw and lifts the midface. That claim is not supported: adult facial bone does not remodel in response to tongue position, and the orthodontic literature the practice borrows from concerns growing children, where jaw development is genuinely still in progress. What the practice can plausibly affect is muscle tone and habitual posture — how the jaw and neck are carried — and those do change how a jaw reads without changing the gonial angle underneath. Anyone measuring their jaw before and after should expect the number to move with body composition and camera angle first.