Do insurance compies approve you first then you do the pre-op liquid diet?

I am curious, because if you lose enough weight during the pre-op liquid diet and it places you under 40 BMI will the insurance still pay for the surgery????

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11/11/08 Surgery with a 10cc band
Weight 214, was 254 pre-op
First fill:11/11/08 3cc (lost .5cc from surgery fill)
Second fill: 12/10/08 1.5cc
Third fill: 1/14/09 1cc
Fourth fill: 1/28/09 1.5cc (lost 1cc from 1/14/09)
Fifth fill: 3/17/09 1cc
Total 6.cc