Any form of surgery regardless of what it affects or is being conducted upon is an extremely traumatic experience for the body and therefore it falls upon the doctor to ensure that the potential benefits of the surgery actually outweigh the potential risks involved.
However, you as the patient should also ensure that you are intimately aware of the potential benefits and risks of the surgery as well as the expected recovery time. You may find that you have to take time off work in order to fully recuperate and so you may need to make alternative arrangements in order to support yourself financially.
Weight loss surgery is primarily carried out whenever a person has excess levels of fat in their body and whilst it is primarily carried out on the basis of medical necessity this particular type of surgery is also conducted for cosmetic purposes as well.
This particular type of surgery (the medical term being bariatric surgery) is used to tackle the root cause of weight gain, by suppressing the natural appetite urges of the person who undergoes the surgery. This surgery (for those who may have reservations about it) will not impact the actual absorption of food and so the digestion process is left untouched.
It is simply imperative that if you do undergo this type of surgery that you duly comply with any and all instructions that your surgeon will provide you to the absolute letter with as little deviation as possible.