Kybella eliminates fat cells by burning them up, processing the waste, and then flushing out the waste using natural processes. Once the cells have been eliminated, they can’t come back—even if you gain weight. Of course, some fat cells will remain after treatment, and these will expand if you gain significant weight. However, since there are less fat cells in the submental area, the degree of submental fullness will be vastly lesser than before the Kybella treatment.