I am curious about the effects and side effects of filler treatment for sunken cheeks.

My cheeks look sunken as I lose weight in my face. I heard that filler treatments are fast and effective for filling in the lost volume.
I am worried that fillers might look a bit artificial, so I would appreciate recommendations for a procedure that can add volume naturally.
It seems like the effect of fillers wears off over time, so I am also curious how long they usually last after just one injection.