You are going to have to contact Kaiser and ask them. Certain procedures are covered by insurance companies but you may not have that coverage in your particular plan, so you never know unless you ask first.
Depending on your obesity condition, Kaiser will more than likley find ways to deny your potential claim. Consider your level of obesity and plan to save for at least half of the cost of the procedure. Unless your have morbid obesity, do not expect Kaiser to pay for any portion of the surgery, which could be considered elective.
They probably will, however you will have to go through a lot of tests before they will. The process takes about six months before they will approve you for surgery.