Doctor Q

This has not been well studied. One study from Scandinavia showed no difference in weight loss when people drank during meals. Many of my successful gastric bypass patients, as well as sleeve and band patients, do drink small amounts during meals. The key is not to drink liquids with the sole purpose of forcing in more food. Remember, speed-eating champions (with normal stomachs) will sip Water while they pound down their hotdogs. Mimicking the eating patterns of the world's speed-eating champions is probably not a great way to eat on a regular basis.

I advise my patients to drink a glass of water (or some calorie-free beverage) about 15 minutes before they have a regular meal. This prevents them from being thirsty when they start a meal. It also helps to "flush through" thick saliva that may cause food to get stuck inappropriately. If the "pipes are clear" every time they eat (band, bypass, sleeve, whatever..) their eating experience will be more consistent.

It's interesting to hear the "reasons" given. As a surgeon on the editorial board for the Journal Obesity Surgery, I can assure you that I have not seen good studies indicating that people should not drink during a meal.
It does seem intuitive to think it matters, but as I stated, it really only matters if someone is trying to "cheat" their surgery, and anyone that does that is destined for failure anyway.