How to tell if I am 200% overweight?

I am wanting to have Gastric Byp surgery and my insurace told me they would only cover it if I am 200% overweight. Well I'm not sure how to tell if I am or not. If you know how to tell or if you can tell me if I am please let me know my % of overweight. I am 18 years old, 5'9" 375 lbs, BMI is 56.