I have pictures of myself as a teenager (I'm 58 now) and I had a saggy chin even then. I have asked all sorts of people -- exercise gurus and trained massage therapists, who presumably have studied human musculature, what one can do to get rid of the skin hanging down below my chin. All of them say that nothing short of surgery (hopefully a little gentler than a meat cleaver
) will do the job. The reason is that there really aren't any muscles there that can be tightened up -- yeah, I've seen ads for those chin exercise products as well, and the exercise people I've talked with say they don't work.
The fat that makes up a double chin will go away (or at least lessen) when you lose weight, but unfortunately only your own genetics will direct where you lose the fat. The loose skin is also genetically determined. I'm pleased that some of you are able to get back your flat chin when you lose weight, but that's your fortunate genetics at work. Some of us aren't so fortunate. We just smile at the world and give them something else to look at.
Please keep in mind that the discussion above has touched on skin, muscle and fat. All three are different things, and all three require different responses by the person wishing to make a change. In this case, losing fat via dieting might help if you're lucky, toning muscles won't help because that isn't what's sagging, and saggy skin requires a little help from the outside via a (very teensy doctor-manipulated) meat cleaver.