GIP and GLP-1 agonists help to control your blood sugar, but people taking them also tend to lose weight. GLP-1, the key hormone involved, slows down how fast your stomach empties food (called gastric emptying). And in addition to causing your pancreas to release insulin, they also block a hormone that causes your liver to release sugar (glucagon). Together, these functions can help you feel less hungry, causing you to eat less food and lose more weight.