Gastric Bypass vs Gastric Sleeve

Gastric sleeve and gastric bypass are the two most common weight-loss operations in North America. Both are done through small incisions, both make the stomach smaller, and both change the gut hormones that control hunger and fullness. Most people feel full sooner and less hungry between meals after either one.

The main difference is what happens to the stomach and the intestine.

How a gastric sleeve works

In a sleeve gastrectomy, the surgeon removes about 80% of the stomach and leaves a narrow tube about the shape of a banana. Food still follows its usual path through the stomach and the intestine.

The smaller stomach holds less. The part that is removed makes most of the hunger hormone ghrelin, which is one reason appetite drops.

How a gastric bypass works

In a Roux-⁠en-⁠Y gastric bypass, the surgeon makes a small pouch at the top of the stomach, about the size of an egg, and joins it to a lower part of the small intestine. Food skips most of the stomach and the first part of the intestine. The rest of the stomach stays in place but no longer holds food.

What long-term trials found

Two randomized trials, in Finland and in Switzerland, compared the two operations directly. A large US study followed tens of thousands of people.

• In the Finnish SLEEVEPASS trial, people had lost about 44% of their excess weight 10 years after a sleeve, and about 51% after a bypass (median values).
• In the Swiss SM-BOSS trial, excess BMI loss at five years was about 61% after a sleeve and 68% after a bypass. The difference was not statistically significant.
• In the US study of more than 65,000 people, average total weight loss at five years was about 19% of starting weight after a sleeve and 26% after a bypass.

In both trials, many people had better blood sugar, blood pressure and sleep apnea after either operation. In SLEEVEPASS, high blood pressure went into remission more often after a bypass.

Side effects and risks

Every operation has risks, and your surgeon goes through the ones that apply to you. In general:

• Early complications. In the US study, serious problems in the first 30 days were about half as common after a sleeve (2.6%) as after a bypass (5.0%).
• Reflux. A sleeve can cause new heartburn or make existing reflux worse. In SM-BOSS, reflux got worse in about 32% of people after a sleeve and 6% after a bypass. A bypass is often suggested for people who already have significant reflux.
• Vitamins and minerals. Everyone needs daily vitamins for life after either operation, but low iron, vitamin B12 and calcium are more common after a bypass, because part of the intestine is skipped.
• Dumping syndrome. Feeling sick, sweaty or shaky after sweets is more common after a bypass, although it can happen after a sleeve too.
• Ulcers and blockages. After a bypass, ulcers can form at the new connection, and the rerouted intestine can become blocked. Smoking and anti-inflammatory painkillers raise the risk of ulcers.
• Reversibility. A sleeve cannot be reversed, because part of the stomach is removed. If needed, it can later be converted to another operation.

Which one is right for you?

There is no single best operation for everyone. Canadian guidelines recommend choosing the procedure together with an experienced team, based on your health, your goals and how you feel about the side effects. Things that often shape the choice:

• Reflux: if you already have significant reflux, a sleeve may not be the best fit.
• Type 2 diabetes or a higher BMI: an operation that includes an intestinal bypass may have a stronger effect.
• Vitamins and follow-⁠up: a bypass asks for closer attention to supplements and bloodwork for life.
• Your history, including earlier operations on your belly.

At 360 Sleeve, our surgeons perform the gastric sleeve, the Roux-⁠en-⁠Y gastric bypass and SADI-⁠S, a sleeve combined with a single intestinal bypass, which is often discussed for people with a higher BMI or type 2 diabetes. For people who already had a bypass, we offer TORe and other revision options. In Ontario's publicly funded program, gastric bypass is the operation done most often. About the gastric bypass at 360 Sleeve.