Bariatric Journal

Gastric Bypass Surgery Side Effects

Discover the Possible Side Effects of Gastric Bypass Surgery, and How to Avoid Side Effects of Gastric Bypass.

Despite the wide acceptance of bariatric surgeries as a panacea to the growing prevalence of obesity, unwanted effects of these surgeries have been the main discouraging factors for many obese people. Gastric bypass side effects occur as consequences of the manipulation of the digestive tract anatomy or weight loss itself.

In gastric bypass surgery, the stomach size is reduced by creating a pouch and bypassing a more significant portion of it. The small intestine is then connected to this small stomach pouch. Also, the intestine is re-aligned in a way that significant length of it is excluded from digestion and absorption. The overall effect of this anatomical alteration is a reduction in food intake as well as absorption of nutrients.

However, the good news is that most of these side effects can be managed appropriately with minimal impact on overall wellbeing. Furthermore, the benefit of losing weight in obese individuals outweighs the side effects of gastric bypass surgery. Thus, gastric bypass side effects should not be a barrier to undergoing gastric bypass surgery when there is an indication of it.

Common side effects are dehydration, dumping syndrome, gallstone, nutritional deficiencies, fecal incontinence, hair loss, etc. These should not be convinced with the complications of the surgery.

With a reduction in the absorptive surface, the amount of water absorbed by the intestine is reduced. This, coupled with inadequate water intake, may lead to dehydration. Adequate water intake (at least 2litres of water per day) is recommended. This should be taken in smaller quantity at a time to prevent distention and permanent enlargement of the stomach pouch.

Obesity is a known risk factor for the formation of gallstone. Many obese patients may, therefore, have a stone(s) in their gallbladder or bile duct before gastric bypass surgery. This has been attributed to high cholesterol level and a malfunctioning gallbladder. Nevertheless, rapid weight loss that accompanies gastric bypass surgery may be a precipitant for stone formation within the gallbladder. Removal of the gallbladder may be required in symptomatic cases.

The malabsorptive component of gastric bypass surgery predisposes to nutritional deficiencies. Nutritional supplements form an essential component of the post-op diet. Hair loss occurs as a result of zinc deficiency but may also be due to rapid weight loss or part of the metabolic body response to surgery. This is however transient.
Dumping syndrome is another side effect of gastric bypass surgery. It is the manifestation of the rapid emptying of the stomach contents into the small intestine coupled with accelerated absorption of glucose into the bloodstream. According to Kanth, up to 50%, 0f patient will develop dumping syndrome after gastric bypass surgery. It occurs due to a reduction in the reservoir capacity of the stomach, disruption of stomach innervation and alteration of the emptying mechanism of the pylorus (Kanth, 2016).

The manifestation of dumping syndrome can be early or late. Early manifestations occur within one hour after a meal, and the symptoms include early satiety, abdominal discomfort, vomiting or diarrhea. These symptoms are the consequences of accelerated emptying of hyperosmolar stomach contents into the intestine which trigger movement of water from the intravascular compartment into the lumen of the small intestine.

Late symptoms come within one to three hours after a meal. The rapid dumping is followed by absorption of glucose into the circulation. This, in turn, triggers insulin release from the pancreas and the glucose is rapidly mopped up. The symptoms are therefore those of hypoglycemia (reduced blood sugar): sweating, headache, palpitation, tremor, blurring of vision, flushing, confusion, etc.

Another side effect that is related to dumping syndrome is fecal incontinence which is seen in those with the underlying weak anal sphincter. Diarrhea in dumping syndrome exposes a pre-operative sphincter weakness.

Difficulty in swallowing may follow gastric bypass surgery due to the small stomach pouch and increase in intragastric pressure. This can be relieved by eating a small meal at a time and also by gradually moving from liquid meal to semisolid and substantial meal.

In conclusion, gastric bypass surgery comes with few side effects which are mostly transient, partly preventable with minimal impact on quality of life. The weight loss and improvement in comorbid conditions are more significant benefits of gastric bypass surgery than any side effect.


Kanth, R. (2016, March 3). Dumping Syndrome: Background, Pathophysiology, Etiology. Retrieved from

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