Common side effects include nutritional deficiencies, nausea, and acid reflux. Some long-term side effects or potential complications depend on the type of obesity surgery.

Obesity surgery, often referred to as bariatric surgery, is an effective method for significant weight loss and managing obesity-related health conditions.

But, like any surgical procedure, side effects and risks are possible. It’s important to know about all possible outcomes before undergoing surgery.

People undergoing bariatric surgery usually report symptoms such as:

  • nausea
  • vomiting
  • constipation
  • diarrhea
  • nutritional deficiencies
  • hypoglycemia (low blood sugar)
  • acid reflux
  • gallstones
  • sagging or loose skin

Though uncommon, surgical complications include:

  • reactions to anesthesia
  • heavy bleeding
  • infection
  • blood clots

The exact side effects and risks depend on the type of bariatric surgery.

Gastric sleeve, also known as vertical sleeve gastrectomy, involves the removal of a significant portion of the stomach. This leaves a narrow sleeve-like structure that limits food intake.

Common side effects include:

In rare cases, gastric sleeve surgery can cause:

Also known as Roux-en-Y gastric bypass, this procedure involves creating a small stomach pouch and connecting it directly to the small intestine, bypassing a significant portion of the stomach and digestive tract.

Dumping syndrome is more commonTrusted Source after gastric bypass than other types of bariatric surgery. It occurs when food moves too quickly from your stomach to your small intestine.

Early dumping syndrome, which occurs within 30 minutes of eating, can cause:

  • bloating
  • cramps
  • nausea
  • vomiting
  • diarrhea
  • flushing
  • dizziness
  • palpitations (rapid heartbeat)
  • fainting

Late dumping syndrome occurs 1 to 3 hours after eating, can cause:

  • sweating
  • flushing
  • dizziness
  • weakness
  • fatigue
  • tremors (shaking)
  • palpitations
  • fainting

If left untreated, dumping syndrome may lead to malnutrition.

Other commonTrusted Source complications include:

  • stenosis can cause dysphagia (difficulty swallowing) and solid food intolerance
  • marginal ulcers, which can cause upper abdominal pain
  • cholelithiasis (gallstones), which are often asymptomatic
  • small bowel obstruction (SBO), which can cause abdominal cramping and vomiting

Research suggestsTrusted Source that people who have undergone gastric bypass are at increased risk of developing alcohol use disorder when compared with other types of bariatric surgery.

In rare cases, gastric bypass surgery can cause:

This procedure involves placing an adjustable band around the upper portion of the stomach, creating a smaller pouch that limits food intake.

For many people, this results inTrusted Source food intolerance. Symptoms may develop if you swallow food that is too large to pass through the newly narrowed opening to the bottom of the stomach or if the band is too tight.

Food intolerance can cause:

  • dysphagia
  • nausea
  • vomiting
  • heartburn
  • bloating
  • abdominal pain
  • GERD

If left untreated, ongoing food intolerance may lead to malnutrition.

Other common complications include:

  • band slippage, which occurs when the band moves from its original location, often resulting in reflux
  • outlet obstruction, which occurs when food is stuck between your pouch and lower stomach, preventing you from eating
  • esophageal or pouch dilation, which can result from an obstruction, causing nausea, reflux, and vomiting

In rare cases, adjustable gastric band surgery can cause:

Also known as “mixed surgery,” BPD-DS involves removing a large portion of the stomach and rerouting the intestines to significantly reduce nutrient absorption.

Common side effects include:

  • diarrhea
  • reflux
  • bloating
  • increased flatulence

BPD-DS is often associatedTrusted Source with deficiencies in:

If left untreated, ongoing deficiencies may lead to malnutrition.

Other common complications include:

In rare cases, BPD-DS can cause:

  • bowel obstruction
  • hernia
  • anastomotic leak

A 2017 study analyzed data on 1,709 people who received bariatric surgery at Obesity Center Amsterdam between November 2007 and February 2015. Approximately 20% of people developed a short- or long-term complication.

Although some side effects improve or resolve in the weeks following surgery, some complications may persist for months or years. In some cases, complications may not become apparent until several years later.

A healthcare professional can discuss your options for bariatric surgery and recommend the safest procedure for your situation. Our FindCare tool can help you find a specialist near you if you don’t already have a bariatric doctor.