Risks of weight loss surgery

The rapid weight loss associated with weight loss surgery can cause a number of side effects and has a number of risks.

These are outlined below.

Complications immediately after surgery

Complications that can occur during or immediately after surgery include:

  • infection this affects around 1 in 20 people
  • blood clots in the legs ( DVT ) or lungs ( pulmonary embolism ) this affects around 1 in 100 people
  • internal bleeding this affects around 1 in 100 people

Excess skin

While weight loss surgery can successfully remove the fat in the body, it can't cause skin to revert to its pre-obesity tightness and firmness.

Therefore, if you were obese, especially for many years, you may be left with excess folds and rolls of skin, particularly around the breasts, tummy, hips and limbs.

These folds and rolls normally become most apparent 12-18 months after surgery. They can look ugly and are difficult to keep clean, so you may be vulnerable to developing rashes and infections.

Cosmetic surgery can be used to remove the excess skin. However, as this treatment is for cosmetic and not clinical reasons, it's not available on the NHS.

The price for a course of skin removal treatment can range from 1,500 to 6,000, depending on the amount of skin that needs to be removed.


Around 1 in 12 people develop gallstones after weight loss surgery, typically 10 months after surgery.

Gallstones are small stones, usually made of cholesterol, that form in the gallbladder.

In most cases, gallstones don't cause any symptoms. However, if they become trapped in a duct (an opening or channel), they can irritate and inflame the gallbladder and cause symptoms, such as:

  • a sudden intense pain in your abdomen (tummy)
  • nausea and vomiting
  • jaundice

Psychosocial effects of surgery

While most people who undergo weight loss surgery report an improvement in their quality of life, several psychosocial effects may be related to rapid weight loss.

Some people have reported relationship problems with their partner as their partner begins to feel nervous, anxious or possibly jealous about their weight loss.

Social occasions that revolve around food, such as family meals, can become awkward, as it's common to feel self-conscious about your reduced capacity to eat.

It's also common for a person to experience a worsening of mood when their weight stabilises, typically two years after surgery. This is often because many people realise that problems that existed before surgery, such as money worries or difficulties at work, are still there.

You may find it useful to discuss these issues with people who have also had weight loss surgery. The British Obesity Surgery Patient Associations website contains a service directory of support groups in the UK.

Stomal stenosis

A common complication in people with a gastric bypass is that the hole (stoma) connecting their stomach pouch to their small intestine becomes narrowed and may getblocked by a piece of food. This is known as stomal stenosis and is thought to occur in one-fifth of people with a gastric bypass.

The most common symptom of stomal stenosis is persistent vomiting.

Stomal stenosis can be treated by directing a small flexible tube, known as an endoscope, to the site of the stoma. A balloon attached to the endoscope is inflated to unblock the stoma.

The best way to prevent stomal stenosis is to always cut food into small chunks, chew the chunks thoroughly and avoid drinking during meals.

Gastric band slippage

Gastric band slippage is a complication affecting around 1 in 50 people with a gastric band.

As the name suggests, the band slips out of position. Thismeans the stomach pouch becomes bigger than it should be. This can cause symptoms such as:

  • heartburn
  • nausea
  • vomiting

Further surgery will be required to repair the band.

Food intolerance

Around 1 in 35 people with a gastric band develop a food intolerance, often many years after their surgery.

A food intolerance is when your body is unable to tolerate certain foods, such as red meat or green salad, resulting in a number of unpleasant symptoms, such as:

  • nausea
  • vomiting
  • gastro-oesophageal reflux disease

The reason why a food intolerance can develop after surgery is unclear.

In most cases, avoiding foods that trigger a reaction should improve symptoms, but if you have persistent symptoms associated with a number of different foods, it may be necessary to remove the band and replace it with a gastric bypass.


No surgery is entirely safe and all surgical procedures carry a risk of death. However, the outlook for weight loss surgery has greatly improvedwith modern techniques.

The risk of death in hospital afterhaving any kind of weight loss surgery is around 1 in 1,000.

Complications of weight loss surgery that could lead to deathinclude:

  • a pulmonary embolism that causes serious breathing difficulties and then death
  • internal bleeding
  • infection
  • heart attack stroke

A number of risk factors have been identified that increase the risk of death during or shortly after weight loss surgery. These are:

  • being over 45 years old
  • high blood pressure
  • having a BMI of 50 or above
  • being male, asobese men tend to weigh more than obese women
  • having a known risk factor for a pulmonary embolism

Known risk factors for a pulmonary embolism include:

  • having a previous history of blood clots
  • pulmonary hypertension when the blood pressure inside your lungs is particularly high
  • obesity hypoventilation syndrome when you have persistent breathing difficulties related to your obesity

The risk factors above can have a significant impact on your individual risk of death. However, untreated obesity, especially morbid obesity, carries a significant risk of premature death itself.

In most cases, the benefits of surgery outweigh the risks in people who meet the National Institute for Health and Care Excellence's criteria for weight loss surgery.


Medically Reviewed by a doctor on 8 May 2015