How Does the Gastric Sleeve Work to Help People Lose Weight?

Understanding how weight-loss surgery works

Woman smiling after recovering from gastric sleeve procedure.

Understanding how weight-loss surgery works

Imagine feeling full after a meal without eating nearly as much as you did before — and losing a lot of weight in the process. That is the goal of gastric sleeve, one of the leading types of bariatric or weight-loss surgeries today.


“Gastric sleeve is a minimally invasive procedure that restricts the volume of food one can eat and decreases appetite,” says Mark Takata, MD, a bariatric surgeon at Scripps Clinic. “It is a very powerful weight-loss tool.”


Gastric sleeve is not for everybody who is overweight, but if you’re severely obese with another medical condition that could be improved if you lost the excess weight, you may be a candidate for this life-altering procedure. You’ll need to learn the risks and benefits before proceeding. If you’re eligible, there are many health benefits to consider that could outweigh any of the potential side effects.

What is gastric sleeve?

Gastric sleeve — also known as laparoscopic sleeve gastrectomy — helps patients lose weight by removing approximately 80 percent of their stomach using minimally invasive surgical techniques.


In gastric sleeve, a bariatric surgeon makes several incisions in the abdomen and inserts a laparoscope — an instrument with a tiny camera that sends pictures to a monitor — and other medical instruments needed to perform the surgery. The surgeon removes a large portion of the stomach and creates a new one with the remaining portion — which is formed into a sleeve-shaped tube. The resulting smaller stomach can hold only two ounces of food at any given time, compared to the average stomach, which can hold up to two quarts.

How does gastric sleeve work?

With gastric sleeve, there are two things at work. The first is oral restriction. With a much smaller stomach, there is much less room to receive food. As a result, patients are not able to eat as much food as they did before.


The second is a physiologically diminished appetite. Removing most of the stomach produces chemical changes in the body that decrease appetite. Specific hormones, such a ghrelin and leptin, control appetite and energy balance and have a profound link to obesity. “By removing the portion of the stomach that produces these hormones, gastric sleeve alters the hormonal balance and dramatically diminishes appetite,” Dr. Takata explains.

Who is candidate for bariatric surgery?

To be a good candidate for bariatric surgery, you must:


  • Have a body mass index (BMI) of 40 or more (100 pounds over your recommended weight)
  • Have a BMI between 35 and 39.9 and a serious obesity-related health problem, such as Type 2 diabetes, coronary heart disease or severe sleep apnea


“These are generally patients who’ve been unable to bring down their weight by other means,” Dr. Takata says.

How much weight will I lose?

Generally, in the first six months to one year after surgery, about two-thirds of all the excess weight will be lost, if patients follow these guidelines:


  • Exercise at least one hour, four days a week
  • Limit snacking to two to three times per day most days of the week
  • Maintain adequate protein intake 
  • Avoid high-calorie, high-sugar drinks


As with any surgery, there are potential risks involved, such as infection, which is why it’s crucial that you stay informed before and after the procedure.


“Gastric sleeve surgery requires a commitment to living a healthier lifestyle,” Dr. Takata says.


“After surgery, the patient must follow a strict diet that enables the body to recover and get used to a smaller stomach. Thereafter, the patient must transition into a lifetime of healthy eating.”