Not uncommon to have some hollowing in this area with weight loss. A good option is to put some HA filler into the lower lid to provide some volume. The best ones to use are Restylane and Belotero. Stay away from Juvederm here as it can result in unwanted edema. The filler should last at least a year. And if you don't like it for some reason it can be easily removed.
There are various options for filling the hollow area under eyes including filler injection, fat injection, and tear trough implant. Lower blepharoplasty may be another option. See an oculoplastic specialist for evaluation.