Laparoscopic Adjustable Gastric Band

In this type of surgery, the surgeon places a ring with an inner inflatable band around the top of your stomach to create a small pouch. This makes you feel full after eating a small amount of food. The band has a circular balloon inside that is filled with salt solution. The surgeon can adjust the size of the opening from the pouch to the rest of your stomach by injecting or removing the solution through a small device called a port placed under your skin.
After surgery, you will need several follow-up visits to adjust the size of the band opening. If the band causes problems or is not helping you lose enough weight, the surgeon may remove it.
The U.S. Food and Drug Administration (FDA) has approved use of the gastric band for people with a BMI of 30 or more who also have at least one health problem linked to obesity, such as heart disease or diabetes.
 
Source  https://www.niddk.nih.gov/health-information/weight-management/bariatric-surgery/types