R13 Actually pre-bariatric diets aren't all that restrictive. The pre-LapBand program I went through was about a year of all sorts of tests, psych eval, support groups, etc. All designed to be educational, but also to "weed out" the people who weren't prepared to take the surgery, recovery and life post-surgery seriously.
There was no specific diet, but in order to have the surgery candidates were required to have lost 5% of their body weight from the time they started the process. I went to my doctor, Jan 2nd of the year I had my surgery, was "officially" weighed (I had a copy of the documentation), I was serious enough that I finished all "the steps" by August of that year-it took most people about twice that time, and losing the 5% was very do-able.
A Tip: Jan. 2nd is probably the best time to have your first weigh-in, since it's right after the whole Halloween-Thanksgiving-Christmas-New Year's "eating holidays."
The reason for the 5% requirement is because a person losing weight actually has a smaller liver than someone gaining weight. It makes the surgery, especially if it's laparoscopic, safer. I don't know why exactly-but it's what I was told.
The most important thing I can say is this: Don't be ashamed by having to do this. People who are overweight, chubby, fat, even obese, have tons of self-control. They're not, and I wasn't, self-indulgent, lazy or some sort of glutton. People who are naturally thin have no idea how much food we DIDN'T eat in our lifetimes, how much we deprived ourselves, how guilty we felt.
The truth is we are simply the product of evolution. We are here because our ancestors could survive starvations, could store fat efficiently and had lived for generations upon generations-going back millions of years-barely ever having enough to eat and intuitively seeking out more food. We live in a world of fast-food outlets everywhere (99 cent "value meals"), candy bars surrounding every cash register, awash in soda and most importantly of all; a whole industry dedicated to the science of making high calorie, high sugar, high fat food irresistibly addictive, and I do mean addictive.
Almost no one understood why I had Lap-band surgery. "You're not that big," they all said, and in a world where sweatpants and T-shirts come in size XXXL, a culture where diabetes is a rite of passage that comes along with cholesterol, erectile dysfunction and high blood pressure drugs-maybe I wasn't.
But, I didn't want to be part of that world, and with Lap-band I'll never have to be. It was one of the best decisions I ever made. I would never advise anyone to have gastric by-pass, but Lap-band is a miracle.