Generally insurance companies pay for procedures that give functional improvement. Although there are some functional benefits to tummy tuck and liposuction, they are virtually always considered cosmetic by insurance companies. Neither of those procedures are a treatment for obesity.
Forget about anything considered "Cosmetic" as no insurance will cover this unless there is significant functional reasons like breast asymmetry (such as a congenital condition or after mastectomy for cancer). A tummy tuck will also never be covered by insurance, but occasionally a panniculectomy will. This is a term for removing only the apron of skin at the lower tummy area and only if it is very severe and causes problems like recurrent infection, rashes, etc .This procedure is done for medical indications and not for cosmetic reasons.