Most likely, your health insurance will not cover skin removal expenses after losing weight unless the excess skin poses other and concurrent health concerns. These expenses would typically be considered as cosmetic and thus, not covered by most plans. However, if you choose a covered surgery, such as breast reduction, skin removal would be likely covered.
It depends of the coverage of your particular plan. If you have a good plan, the surgery might be covered; however, most insurance companies regard this as "elective cosmetic surgery", which is typically not a covered item. You should read your policy or call your insurance agent to find out.
Cosmetic procedures are typically not covered under most insurance plan unless it is causing detriment to your health or chronic pain (such as breast reduction for back pain). However, you may be able to save considerably if you donate the skin to one of the burn centers across the nation.