1. because you were also on weight loss
diet, it is possible that due to restricted food items in your menu you might have been deprived of essential minerals, vitamins and nutrients which might have led to formation of dark circles
which also occur due to lack of sleep or unusual mental stress
2. dark circles means oxidised hemoglobin:so it is possible that you may have iron deficiency anemia
, please check with your attending Physician regarding the same.