How to get rid deep tear trough and sunken eyes?

not necessarily. Often times, volume loss in the under eye region with deep tear troughs may be genetic and/or age-related. Non-invasive treatments include soft tissue fillers (see link below). Surgical treatments include volume-enhancing implants or lower eyelid surgery with fat repositioning. The latter procedure is best if you have lower eyelid bags in addition to the deep tear troughs and essentially moves the fat from the bag into the tear trough.

If you are underweight by 20 kgs and you notice a tear trough deformity, go ahead and gain the 20 kgs that will bring your weight back upto normal, then you can evaluate your facial volume to see if your concerns still  exist.