There are five main weight loss surgeries performed today, though two of them, sleeve gastrectomy and gastric bypass, account for roughly 90% of all procedures worldwide. The others include the duodenal switch, single-anastomosis duodenal switch, and adjustable gastric band. A newer non-surgical option called endoscopic sleeve gastroplasty also fills a gap for people who don’t qualify for or want traditional surgery.
Sleeve Gastrectomy
Sleeve gastrectomy is the most commonly performed weight loss surgery in the world. A surgeon removes about 80% of the stomach, leaving a narrow tube roughly the size and shape of a banana. The smaller stomach holds far less food, but the real power of this procedure lies in what happens hormonally. Removing the larger portion of the stomach dramatically lowers levels of ghrelin, the hormone that drives hunger. Patients who’ve had a sleeve report feeling less hungry and more satisfied after meals than both non-obese people and people with obesity who haven’t had surgery.
Beyond appetite suppression, the sleeve speeds up how quickly food leaves the stomach and boosts the release of gut hormones that improve blood sugar control. These overlapping changes help explain why the sleeve works for weight loss and also improves conditions like type 2 diabetes. The procedure is permanent and not reversible.
Roux-en-Y Gastric Bypass
Gastric bypass, formally called Roux-en-Y gastric bypass (RYGB), is the second most common procedure and has decades of outcome data behind it. The surgeon creates a small pouch from the top of the stomach and connects it directly to the middle section of the small intestine, bypassing most of the stomach and the upper intestine entirely. This means food skips a significant stretch of the digestive tract, which reduces both how much you eat and how many calories your body absorbs.
The metabolic effects are substantial. Within months of surgery, patients typically see significant drops in fasting blood sugar, LDL cholesterol, triglycerides, and markers of body-wide inflammation. Insulin resistance improves sharply. In studies of patients with type 2 diabetes before surgery, the condition resolved entirely in some cases. Patients generally lose between 33% and 55% of their excess weight, though individual results range widely. The trade-off is that bypass is a more complex operation than the sleeve, with a small risk of leaks at the surgical connections (about 0.9% in primary surgeries) and bowel obstruction (about 0.7%).
Duodenal Switch
The biliopancreatic diversion with duodenal switch (BPD-DS) is the most aggressive weight loss surgery available. It combines a sleeve gastrectomy with an extensive intestinal bypass, rerouting food so that digestive enzymes only mix with it in the final stretch of the small intestine. This produces the greatest average weight loss and the highest rates of long-term diabetes remission of any bariatric procedure.
That effectiveness comes with a cost. The duodenal switch carries the highest risk of nutritional complications among all bariatric surgeries. About 75% of patients in one referral study needed treatment for malnutrition. Common deficiencies include iron, calcium, protein, B vitamins, and fat-soluble vitamins like A, D, E, and K. Every patient needs lifelong vitamin supplementation and regular blood work to catch deficiencies before they cause serious problems. Because of these demands, this surgery is typically reserved for people with the highest BMIs or those who haven’t lost enough weight with other procedures.
Single-Anastomosis Duodenal Switch (SADI-S)
The SADI-S is a simplified version of the traditional duodenal switch. Instead of two intestinal connections, the surgeon makes only one, which shortens the operation and may reduce certain surgical risks. It pairs a sleeve gastrectomy with a single loop of rerouted intestine.
Long-term results look similar to the traditional duodenal switch. After five or more years, 91% of SADI-S patients maintained at least 20% total body weight loss, compared to 96% of traditional duodenal switch patients, a difference that wasn’t statistically significant. Nutritional deficiencies remain common: about 64% of SADI-S patients experienced vitamin or micronutrient deficiencies during follow-up, 48% developed iron deficiency, and 42% developed anemia. Acid reflux affected about 35% of patients over the long term. Like the traditional duodenal switch, SADI-S requires committed follow-up and lifelong supplementation.
Adjustable Gastric Band
The adjustable gastric band (often known by the brand name Lap-Band) was once one of the most popular weight loss procedures. A silicone band is placed around the upper portion of the stomach, creating a small pouch that limits how much food you can eat at once. The band can be tightened or loosened through a port under the skin, and the procedure is fully reversible.
In practice, the band has fallen sharply out of favor. Long-term studies show complication rates approaching 47%, with major complications in nearly 38% of patients. The most frequent problems include the band slipping out of position (about 11%), eroding into the stomach wall (about 8%), and band intolerance, where patients simply cannot tolerate the device (about 13%). In one long-term study, over 35% of patients eventually had their bands removed. Many centers across Europe and North America have largely stopped offering the procedure, shifting to sleeve gastrectomy and gastric bypass as primary options.
Endoscopic Sleeve Gastroplasty
Endoscopic sleeve gastroplasty (ESG) isn’t surgery in the traditional sense. A doctor passes a suturing device down your throat and stitches the stomach from the inside, reducing it to a smaller tube shape without any incisions or organ removal. There’s no cutting, no rerouting of the intestines, and the hospital stay is typically shorter.
The weight loss is meaningful but more modest than surgical options. At 12 months, patients lose about 16% to 17% of their total body weight, which translates to roughly 60% of excess weight. For comparison, laparoscopic sleeve gastrectomy produces about 24% total body weight loss at six months and 28% at two years. ESG still outperforms intensive diet and lifestyle programs: one matched study found 20.6% total weight loss with ESG versus 14.3% with high-intensity diet and behavioral therapy at one year.
ESG tends to be considered for people with a BMI between 30 and 40 who may not qualify for or want traditional bariatric surgery. For BMIs above 40, the evidence more strongly supports surgical options.
Who Qualifies for Weight Loss Surgery
Eligibility guidelines were updated in 2022 by the two largest professional societies in the field, ASMBS and IFSO. The traditional threshold was a BMI of 40 or higher, or a BMI of 35 with obesity-related health conditions like diabetes, sleep apnea, or high blood pressure. The updated guidelines lowered that threshold, recommending surgery be considered for people with a BMI of 35 or above regardless of other conditions, and for people with a BMI of 30 to 35 who have metabolic disease that hasn’t responded to other treatments. For Asian populations, thresholds are lower still because metabolic complications tend to develop at lower BMIs.
What Recovery Looks Like
Recovery after bariatric surgery follows a structured eating progression that takes about two months. For the first day or so, you’ll only have clear liquids. After about a week, you move to strained, blended, or mashed foods. A few weeks later, soft foods are introduced. Around eight weeks after surgery, most people can gradually return to regular solid foods, though portion sizes will be permanently smaller.
The dietary progression is similar across most procedures, though the nutritional monitoring that follows varies by operation. Sleeve gastrectomy and gastric bypass patients need ongoing vitamin supplementation, but the demands are manageable for most people. Duodenal switch and SADI-S patients face a much more intensive supplement and monitoring schedule that continues for life. Skipping follow-up labs or supplements after these more complex procedures can lead to serious deficiencies in protein, iron, calcium, and essential vitamins.