There are side effects, the list includes:
There are a host of gastric bypass side effects that include vomiting, constipation, hair loss, infection, band migration, port problems, band problems, vitamin deficiencies, ulcers, your staples may pull out, etc...
Almost everyone will encounter gastric bypass side effects, and almost every single person will encounter nausea. The good thing is that it generally doesn't last long, and it is mostly at the very beginning of your adventure. Basically you are going to eat too much, too fast, and you are going to get sick. This happens to everyone at least once. If you are vomiting on a regular basis then this is an early warning sign of something bad. Don't panic, most of the time it is something wrong with your diet, but tell your doctor at once if you are vomiting on a regular basis.
Yet another gastric bypass complication is constipation. This happens to many people at the beginning as well. It happens because you are taking in way fewer calories than your body is used to, and that in turn is creating less waste, and that is making it harder to go to the bathroom. This usually goes away in a few weeks, but if it lasts...go to the doctor at once.
Hair loss is hit and miss with many people. You will be eating less, and with eating less comes a lack in nutrition. With a lack of nutrition you will be susceptible to hair loss. This is almost never permanent, and once your body adjusts to the lack of food you will generally regrow the hair that you lost in the first 6 months.
Infections are far less common, but still happen. Infections are often times caused by not properly cleaning the bandages, or skipping out on the post op medications. Keep your wounds clean and take your meds and you will drastically reduce your chances of getting sick.
The final issue to talk about it port problems, it is not very common but I feel it is worth talking about. There have been two types of problems. The first is a dislocation of the port. It may move around or in extreme cases turn upside down, if this happens it will need to be adjusted. This isn't a hard fix, but it is a pain to go back to the hospital. You will have to be put under anesthetic again, but it doesn't take long. The second problem is perforation of the connecting tube close to the port. This can lead to loss of fluid and widening of the opening...and when this happens you will gain weight. This is also not a huge dilemma, but is also a pain. It can be fixed it one day and patients are generally back up and on their feet in 2 days, some later that night.
In closing, there are many gastric bypass complications, but with a firm grip on what they are, you can avoid many of them.