Hair loss is a big problem for some gastric bypass patients. I'm not sure exactly why they get it, but they do. My friend had that problem. It finally did go away, but it took a while.
There are other weight-loss surgery methods that are becoming more popular and don't have as many complications as gastric bypass can have.
My friend was drinking half a gallon of water a day and still got dehydrated. She had to go to the ER three times in six weeks for fluids. She's better now, but it's something she has to watch all the time.