Agreeing that the issue you are noticing is a result of congenital buccal fat, there are several things I would point out and have you consider. First, you are young so it’s good that you are wanting to address this before it changes the integrity of the skin that is starting to displace from the heaviness. You have a nice slender chin shape so I would not get crazy with filling too much in the area of the prejowl sulcus and marionette area though as you get older you like most will need. I wouldn’t advise for the excision surgery either if you can avoid. I personally would try Evoke which is a new non-invasive RF device with a cheek/jawline applicator. With correct settings, treatment time, and number of treatments I believe you could get the reduction in fat tissue and tightening of the skin and underlying tissues to give you that slenderize lower cheek and definition along the jawline that you desire. Hope this is helpful:)
