context: Existing surgeries help with weight loss in different ways. Restrictive surgeries work by shrinking the size of the stomach and slowing down digestion. A normal stomach can hold about 3 pints of food. After surgery, the stomach may at first hold as little as an ounce, although later that could stretch to 2 or 3 ounces. The smaller the stomach, the less you can eat. The less you eat, the more weight you lose. Malabsorptive/restrictive surgeries change how you take in food. They give you a smaller stomach and also remove or bypass part of your digestive tract, which makes it harder for your body to absorb calories. Doctors rarely do purely malabsorptive surgeries -- also called intestinal bypasses -- anymore because of the side effects. Implanting an electrical device, the newest of the three techniques, prompts weight loss by interrupting nerve signals between the stomach and the brain. What it is: Gastric banding is a type of restrictive weight loss surgery. How it works: The surgeon uses an inflatable band to squeeze the stomach into two sections: a smaller upper pouch and a larger lower section. The two sections are still connected by a very small channel, which slows down the emptying of the upper pouch. Most people can only eat a 1/2 to 1 cup of food before feeling too full or sick. The food also needs to be soft or well-chewed. Pros: This operation is simpler to do and safer than gastric bypass and other operations. You get a smaller scar, recovery is usually faster, and you can have surgery to remove the band. You can also get the band adjusted in a doctor's office. To tighten the band and further restrict your stomach size, the doctor injects more saline solution into the band. To loosen it, the doctor uses a needle to remove liquid from the band. Cons: People who get gastric banding often have less dramatic weight loss than those who get other surgeries. They may also be more likely to regain some of the weight over the years. Risks: One of the most common side effects of gastric banding is vomiting after eating too much too quickly. Complications with the band can happen. It might slip out of place, become too loose, or leak. Some people need more surgeries. As with any operation, infection is a risk. Although unlikely, some complications can be life-threatening. What it is: This is another form of restrictive weight loss surgery. In the operation, the surgeon removes about 75% of the stomach. What remains of the stomach is a narrow tube or sleeve, which connects to the intestines. Sometimes, a sleeve gastrectomy is a first step in a series of weight loss surgeries. For some people, it's the only surgery they need. Pros: For people who are very obese or sick, other weight loss surgeries may be too risky. A sleeve gastrectomy is a simpler operation that gives them a lower-risk way to lose weight. If needed, once they've lost weight and their health has improved -- usually after 12 to 18 months -- they can have a second surgery, such as gastric bypass. Because the intestines aren't affected, a sleeve gastrectomy doesn't affect how your body absorbs food, so you're not as likely to fall short on nutrients. Cons: Unlike gastric banding, a sleeve gastrectomy is irreversible. Since it's relatively new, the long-term benefits and risks are still being evaluated. Risks: Typical risks include infection, leaking of the sleeve, and blood clots. What it is: Gastric bypass combines both restrictive and malabsorptive approaches. In the operation, the surgeon divides the stomach into two parts, sealing off the upper section from the lower. The surgeon then connects the upper stomach directly to the lower section of the small intestine. Essentially, the surgeon is creating a shortcut for the food, bypassing part of the stomach and the small intestine. Skipping these parts of the digestive tract means that the body absorbs fewer calories. Pros: Weight loss tends to be swift and dramatic. About 50% of it happens in the first 6 months. It may continue for up to 2 years after the operation. Because of the rapid weight loss, conditions affected by obesity -- such as diabetes, high blood pressure, high cholesterol, arthritis, sleep apnea, and heartburn -- often get better quickly. Gastric bypass also has good long-term results. Studies have found that many people keep most of the weight off for 10 years or longer. Cons: You won't absorb food the way you used to, and that puts you at risk for not getting enough nutrients. The loss of calcium and iron could lead to osteoporosis and anemia. You'll have to be very careful with your diet, and take supplements, for the rest of your life. Another risk of gastric bypass is dumping syndrome, in which food dumps from the stomach into the intestines too quickly, before it's been properly digested. About 85% of people who get a gastric bypass have some dumping. Symptoms include nausea, bloating, pain, sweating, weakness, and diarrhea. Dumping is often triggered by eating sugary or high-carbohydrate foods, and adjusting your diet can often help. Unlike adjustable gastric banding, gastric bypass is generally considered irreversible. It has been reversed in rare cases. Risks: Because gastric bypass is more complicated, it's riskier. Infection and blood clots are risks, as they are with most surgeries. Gastric bypass also makes hernias more likely, which may need further surgery to fix. Also, you may get gallstones because of the rapid weight loss. What it is: An implanted pacemaker-like device sends regular electrical impulses to the vagus nerve, which signals the brain that the stomach is full. The vagus nerve extends from the brain to the stomach. The blockade device is placed under the rib cage and is operated by remote control that can be adjusted outside the body. Pros: Implanting this device is the least invasive of the weight loss surgeries. The outpatient procedure may take up to an hour and a half while the patient is under general anesthesia. Cons: If the battery completely drains, a doctor has to reprogram it. Side effects can include nausea, vomiting, heartburn, problems swallowing, belching, mild nausea, and chest pain. Risks: Infection, pain at the implantation site, or other surgical complications. The procedure has a low rate of serious complications. What it is: This is a more drastic version of a gastric bypass. The surgeon removes as much as 70% of your stomach and bypasses even more of the small intestine. A somewhat less extreme version is biliopancreatic diversion with a duodenal switch, or âthe duodenal switch.â It's still more involved than a gastric bypass, but this procedure removes less of the stomach and bypasses less of the small intestinethan biliopancreatic diversion without the switch. It also makes dumping syndrome, malnutrition, and ulcers less common than with a standard biliopancreatic diversion. Pros: Biliopancreatic diversion can result in even greater and faster weight loss than a gastric bypass. Although much of the stomach is removed, what's left is still larger than the pouches formed during gastric bypass or banding procedures. So you may be able to eat larger meals with this surgery than with others. Cons: Biliopancreatic diversion is less common than gastric bypass. One of the reasons is that the risk of not getting enough nutrients is much more serious. It also poses many of the same risks as gastric bypass, including dumping syndrome. But the duodenal switch may lower some of these risks. Risks: This is one of the most complicated and riskiest weight loss surgeries. As with gastric bypass, this surgery poses a fairly high risk of hernias, which will need more surgery to correct. But this risk is lower when the doctor uses minimally invasive procedures (called laparoscopy). What it is: An intragastric balloon is a type of restrictive weight loss surgery in which a deflated balloon is placed in the stomach (through the mouth). Once in place, it is filled with saline solution that provides a sense of fullness, thereby curbing hunger. The intragastric balloon is not meant for people who've had weight loss surgery or who have bowel disease or liver failure. Pros: There's no surgery involved and no hospital stay required. The balloon is temporary; it stays in place for six months. A person can lose about 10 percent of his excess body weight during that time. Cons: Possible stomachache, nausea and vomiting a few days after placement of the balloon. Risks: The FDA in 2017 reported five deaths that may have been caused by the intragastric balloons (e.g., perforation of the stomach or esophagus, or intestinal obstruction). The agency also received multiple reports of spontaneous balloon overinflation, either with air or fluid, and acute pancreatitis caused by the balloon pressing on surrounding organs. What it is: Aspire Assist is a device that takes a malabsorptive/restrictive approach to weight loss. A tube is placed through an abdominal incision that has a disk-shaped port that sits flush against the abdomen outside. About 20-30 minutes after a meal, the patient attaches the tube to an external draining device that removes food matter into the toilet. The device, approved for weight loss in 2016 by the FDA, removes about 30 percent of calories consumed. Pros: In a control study, patients fitted with Aspire Assist lost an average of 12 percent of their total body weight compared to 3.6 percent in patients who combined diet and exercise to lose weight. Another study found that patients lost half their excess weight in the year after placement of the device. The placement of the tube can be done quickly, under light anesthesia. Cons: As patients lose weight, their tube and disk that provides access to the port need to be adjusted so that the disk remains flush against the skin. Frequent trips to the doctor are also necessary to monitor the device and provide counseling. Patients need to get a replacement drain tube after a certain number of uses. Side effects include indigestion, nausea, vomiting, constipation, and diarrhea, according to the FDA. Risks: The surgical placement of the tube can cause sore throat, bloating, bleeding, infection, nausea, pneumonia, and could puncture the stomach or intestine. Patients can feel discomfort, pain, irritation, hardening or inflammation of the skin around the site where the tube is placed. If the tube is removed, it could leave a fistula, an abnormal passageway between the stomach and the abdominal wall. The ideal weight loss surgery depends on your health and body type. For instance, if you are very obese, or if you have had abdominal surgery before, simpler surgeries might not be possible. Talk with your doctor about the pros and cons of each procedure. If possible, go to a medical center that specializes in weight loss surgery. Studies show that complications are less likely when weight loss surgery is done by experts. No matter where you are, always make sure that your surgeon has had plenty of experience doing the procedure you need.