How can I reduce face fat and double chin?

Good for the future. Maintaining or achieving a healthy weight is the primary goal. Excess, disproportionate fat of the neck can be removed with liposuction, but the face is another story. The bad news is, facial fat is not usually treated with liposuction, and while cheek fat pads can be removed, the results are not very dramatic. The good news is that we loose facial fat as we age, so you will look younger longer.
If weight loss. Doesn't take care of it, you might consider liposuction for the "double chin" area.
Lose weight. By simply losing 5 to 10 pounds, you will reduce the fat.