An Omega-loop gastric bypass (also known as a mini-bypass) is a procedure where the stomach is divided into two sections, creating a smaller stomach pouch, then the first part of the small intestine is bypassed, reducing the amount that can be absorbed.
Essentially, the operation aims to reduce the amount of food you can eat due to the smaller stomach pouch, as well as reducing the number of calories that are absorbed from the food you eat, as the food bypasses the first part of the small intestine.