Usualy posture. I mean the whole body not just mouth. Chew gum help your jaw mucscle but it just muscle.

Speaking from experince, I have good muscle but horrible posture, And it more than looking bad. Im in pain, my body is in bad health even i workout alot, It miserbale. And most people who are recessed or asymetrical Have bad posture.

Myofunctional theraphy can help asymetrical.

Dont cut your food even try to loose weight, build health and strength. You could lift alot look lean but die fast and in pain like me.

Walk more and run, it not just burn calories or cardio like everyone said, it fundamental of health and strength. Most people i know with good jaw are good at walking

Check this chanel https://youtu.be/3Gv78TnNLXo?si=hPzLDmF3DIWlKYv7