casagirl,
It depends on who your surgeon is, but some require a pre-op diet of liquid (usually high protein low carb), some require part liquid with one meal a day or some say specific foods prior to surgery. Some require two weeks, some less, some only require liquids for just the night before surgery and some don't have any requirements at all.

Mine has me on liquid protein for 14 days prior to surgery. His reason is that doing so will reduce the fat around the liver making surgery safer and easier. Your liver is in front of your stomach so they will need to move it out of the way to put the band on, if it is fatty, it could get damaged or be in the way of getting the surgery done properly or even having the surgery done at all. I will then be required to do liquids for two weeks after surgery and then graduate to puree then to solids. The reason for liquids/puree after surgery is to allow time for healing.

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MY MILESTONES:
Start 234 lbs.(Size 18 pants, XXL Tops, 42DD bra, 8 shoe, 7 ring)
Banded: 5/30/08
In "Onderland" 8/15/08
1/2 way to goal/50 lbs lost: (185 lbs.) 10/12/08
NORMAL weight BMI (145 lbs.): 3/19/09
Achieved initial goal (137 lbs.)/Set New goal (120 lbs.): 4/28/09
Current weight: 133 lbs. (Size 6 pants, M Tops, 34C bra, 7 shoe, 5 ring)
BMI Countdown: Pre-op: 40.2-Current: 22.8
Total weight lost to date: 101 lbs.-13 pounds to go.