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6 Side Effects of Weight Loss Surgery

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More and more people are opting to undergo weight loss surgery in an attempt to reduce their weight and improve their body composition.

But with invasive surgery comes obvious risks. And even if the operation itself goes well there are a number of complications and side effects that may occur afterwards.

In this article we’ll give you the lowdown on why gastric bypass might not be the best way to achieve your goals.

What is Weight Loss Surgery?

There is an extremely strong link between being overweight and an increased risk of life-threatening disease. At present, these diseases account for around 2.5 million deaths per year worldwide [1].

In order to combat this, the National Institute of Health (NIH) released guidelines for surgical weight loss surgery in the early 1990s. Weight loss surgery was coined as a blanket term for a group of invasive procedures aimed at reducing obesity rates.

Otherwise referred to as bariatric surgery, weight loss surgery is performed on people who wish to lose weight. It is usually intended for those who fall into the obese category and achieve a body mass index (BMI) of at least 40 [2].

Weight loss procedures can be split into either restrictive or malabsorption surgeries

Gastric banding is a restrictive procedure that involves making incisions in your abdomen and placing a band around the top of your stomach. By doing this your stomach is divided into two, with the smaller pouch at the top being unable to take food on. This essentially reduces the volume of the stomach itself and the amount of food you can eat before you feel full.

Sleeve gastrectomy is another restrictive procedure that involves removing part of the stomach as opposed to banding it. Again this reduces the volume of the stomach and reduces the amount you eat.

Malabsorption surgery takes place in the form of gastric bypass. This procedure involves using specialized staples to form a small pouch. The stomach is then connected to your small intestine. By creating this link you are essentially bypassing the remaining part of the stomach, which again decreases the amount you eat.

There are a number of other types of bariatric surgery such as intra-gastric balloon and bilo-pancreatic diversion but as you can see, they are all invasive and all involve surgical intervention.

What Are The Side Effects of Weight Loss Surgery?

Although it is recommended that you aim to lose weight naturally through diet and exercise, many people still choose to undertake weight loss surgery. But as you can imagine, these procedures don’t come without risk.

While weight loss surgery can greatly improve your weight loss success, the side effects can be serious. As such it is important to weigh up the long-term health benefits against the potential side effects before undergoing this procedure.

The list of side effects to bariatric surgery is long and complex, and many are still being discovered. However, here are the ones you need to know about the most.

#1. Dumping Syndrome

According to scientific review, dumping syndrome is a common complication of weight loss surgery [3].

When the stomach is reduced in size you also reduce its functional capacity. This means that you get excess amounts of undigested food entering the next part of the digestive tract – the small intestine. It does this because the stomach very rapidly dumps food without enough time to properly digest it.

Although the science behind it is complex, the small intestine expands too quickly, and the resulting change in pressure forces undigested food into it. This can occur within as little as 15 minutes after eating [4].

If dumping occurs you’ll feel nauseous, dizzy and weak. Swelling of the small intestine and bowels can also lead to abdominal pain and decreased blood volume. You may also suffer from symptoms of osmotic diarrhea – a form of severe diarrhea caused by water retention within the bowels.

#2. Hypoglycemia

One common side effect of dumping syndrome is alimentary hypoglycemia or low blood sugar. Because food is dumped out of the stomach so quickly, the pancreas in turn releases a huge amount of insulin into the bloodstream. Too much in comparison to what i actually needed.

This serious side effect of weight loss surgery is difficult to fix. To maintain a steady blood sugar level you’d need to eat complex, fibrous carbohydrates and plenty of protein – the problem is though that these foods can trigger discomfort and can only be eaten in small amounts due to their volume.

Hypoglycemia can cause sweating, confusion, dizziness and impaired judgment. More severe cases can cause seizures, loss of consciousness and even death. 

#3. Excess Skin

Rapid weight loss will never be without its side effects. When you lose weight through diet, exercise and nutrient-based fat burners you allow a more gradual weight loss which lets the body adapt.

However, with drastic weight loss from bariatric surgery, you don’t allow enough time for your body to adapt. Whilst the surgery itself leads to you losing fat, it cannot help your skin to tighten up. This can lead to excessively loose skin folds particularly around the stomach, chest, hips and limbs. 

A common issue with weight loss surgery is the need for additional cosmetic surgeries afterwards to correct loose skin. This can sometimes be as many as 5 surgeries to fully correct the issue.

#4. Gallstones

One of the more painful side effects of weight loss surgery is the development of gallstones. These are lumps or stones that develop in either the gallbladder or bile ducts. It occurs frequently in obese people and may be linked to high levels of cholesterol in the blood.

Rapid weight loss puts you at a higher risk of gallstones, and around a third of all bariatric surgery patients will experience it [5]. Whilst in most cases this illness will fix itself over time, in some cases you may need a cholecystectomy to remove your gallbladder.

Symptoms include upper abdomen pain and right shoulder pain. Additionally, you may suffer from indigestion, nausea, diarrhea, fever and chills.

#5. Nutrient Deficiency

Malabsorption procedures such as gastric bypass can lead to nutrient deficiency. Because the amount of food and calories that the body can absorb is limited, malnutrition can occur in a number of patients.

There is much more pressure on a weight loss surgery patient to try and get as many nutrient-rich foods into their diet as possible. This means restricting cheat foods to a minimum in favor of fruits and vegetables. A multivitamin is also often needed too.

Food intolerance also occurs in a relatively low percentage of those who’ve had weight loss surgery. Symptoms of intolerance may occur years after the procedure itself and include bloating, abdominal discomfort, migraines and a general feeling of tiredness.

#6. Post-Operative Failure

Such invasive procedures as bariatric surgery are in themselves risky. Although the rate of death within 1-year post-operation is only 1% and 6% at 5 years, things can still go wrong.

Lap band slippage effects around 1 in every 50 people and occurs when adjustable gastric bands slips from its existing position and consequently makes the stomach pouch bigger than it should be. In this case, you’ll likely suffer from reflux and vomiting and further surgery will be needed to rectify it.

Staple failure and disruption is a frequent complication associated with weight loss surgery. More likely to occur with vertical pouches, disrupted staples can lead to weight regain as well as marginal ulceration [6].


Weight loss surgery is not without its complications. There are a number of common side effects that may occur, either cosmetically or directly relating your health. It is important if you are considering bariatric surgery that you weight these up against the potential benefits.

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  1. World Health Organization. World Health Report 2002. Available at:
  2. Buchwald, H et al. Bariatric surgery: a systematic review and meta-analysis. JAMA. 2004; 292(14): 1724-1737
  3. Tack, J et al. Pathophysiology, diagnosis and management of postoperative dumping syndrome. Nature Reviews Gastroenterology and Hepatology. 2009; 6: 583-590
  4. Del Valle, J. Peptic ulcers and related disorders. In Harrison’s Principles of Internal Medicine. 18th ed.
  5. Abell, TL et al. Gastrointestinal Complications of Bariatric Surgery: Diagnosis and Therapy. Am J Med Sci. 2006; 331(4): 214-218
  6. Capella, JF et al. Staple Disruption and Marginal Ulceration in Gastric Bypass Procedures for Weight Reduction. Obes Surg. 1996; 6(1):44-49