Hi there, no the diet plan is completely different. They actually get to eat more and sooner than banded patients. I am assuming that their new digestive system plays a role in the faster weight loss.
My friend has the duodenal switch surgery (similar to gastric bypass) performed one week before my surgery and to-date she has lost 100 lbs. However, she was also hospitalized for 6 weeks due a stomach infection as a result of this surgery.
I researched both and here in Ontario, Canada, we have provincial coverage for Gastic Bypass, I opted for the band and paid for it myself (15K). I absolutely refused to have such an evasive procedure, only to have it fail years down the road.
The difference being, that once you've had the Gastic bypass and your stomach pouch is smaller, you will lose weight, but gradually over time, if you overeat and stretch it, there is no means to reduce it again. With the band, we have fills to tighten things up when the band gets lose due to weight loss or a slight stretch.
I hope this helps answer your question.