Bariatric surgery is basically operation carreid out to make changes in your digestive system to help you lose weight. This is usually done to people who aren't able to lose weight even after following strict diets and exercise. Obesity also causes major problems like excessive weight on the knees and walking issues. In such cases, this surgery is performed.
It is quite safe when performed using advanced technologies, but it does have some  long term side effects like low blood pressure, malnutrition, etc.