Hi, There can be various reasons for undereye dark circles ranging from hereditary to excessive eye strain or sun exposure. Dark circles can be pure pigmentation changes, due to excessive use of kajal and cosmetics or as you have rightly mentioned loss of volume and fat. The best treatment for your problem is under eye fillers which restore the volume there by reducing the dark hollows making you look fresh and youthful. Fillers are injected in the area and last for anywhere between 8 to 10 months. Hope this helps Dr Rashmi Soni Lohiya DDV, DNB. Skinsure clinic.