Bariatric Weight-Loss Surgery

Risks and Side Effects of Gastric Bypass Surgery You Should Know

Dr. Jason F. Moy
Dr. Brian T. Chin
Daniel Roman
July 27, 2021
Risks and Side Effects of Gastric Bypass Surgery You Should Know

Gastric bypass is one of the most popular weight-loss surgeries available. It’s been performed for over fifty years, with the laparoscopic version being introduced in the 1990s. Like other weight-loss surgeries, gastric bypass greatly reduces the capacity of the stomach. 

During gastric bypass surgery, the stomach is split into two sections. The smaller section, which is about the size of an egg, continues to receive food, just like the stomach did pre-surgery. The larger portion remains within the patient but only serves to produce digestive enzymes following surgery, never receiving food.

A lower section of the small intestine is directly connected to the smaller stomach pouch, bypassing the upper section of the small intestine. This reduces the number of calories and nutrients absorbed in the digestive tract after eating. Combined with the smaller capacity of the stomach, this helps the patient achieve accelerated weight loss. 

Although it’s been performed for over five decades, there are risks and side effects that can impact patients who endure this procedure. 

Dumping Syndrome

Gastric bypass surgery results in a smaller stomach capacity, which can lead to dumping syndrome. With this condition, food enters the small intestine before being adequately digested in the stomach. 

Patients who experience early dumping after eating have different symptoms from those who experience it at least an hour after eating. Early dumping symptoms can include bloating, nausea, dizziness, or fainting. Later dumping can cause fatigue, confusion, and hunger. 

Whether a patient suffers from early or late dumping, these symptoms can be disruptive to everyday life. Working with a nutritionist can help to identify which foods could be causing dumping, so patients can avoid these foods and uncomfortable symptoms. 

Malnutrition & Low Blood Sugar

After gastric bypass surgery, the digestive system works differently. The reduced size of the stomach and reconfiguration of the small intestine limits the type and quantity of foods patients can consume. These limitations can cause low blood sugar and/or malnutrition. 

Low blood sugar, or hypoglycemia, can cause faintness, anxiety, and irritability. Severe hypoglycemia can lead to seizures and loss of consciousness if left untreated. Malnutrition can be caused by insufficient levels of a number of essential vitamins and nutrients. The most common nutrients that cause malnutrition in gastric bypass patients include vitamin B-12, iron, and calcium. Patients should monitor their nutrient intake with the help of a nutritionist. Most patients will need the help of supplements to maintain nutrient levels following gastric bypass surgery. 


Since gastric bypass surgery involves cutting into the stomach, the risk of stomach perforation is significant. When digestive fluids leak from the stomach into the peritoneum, the resulting inflammation is called peritonitis. Symptoms of peritonitis include rapid heartbeat, back pain, pelvic pressure, fever, and more. Left untreated, peritonitis can cause serious complications like sepsis and death. 

For many patients, the benefits far outweigh gastric bypass side effects. The resulting weight loss can help patients regain their mobility and cure or reduce the severity of many chronic illnesses. The specialists at BASS Bariatric Surgery Center have many years of experience perfecting their surgical techniques. To learn more about their patient outcomes following gastric bypass, or to inquire more about the process, contact us today at at 925-281-3711.

About The Author

Daniel Roman, Content Writer

Daniel Roman is a Digital Content Writer at BASS Medical Group. He received his Masters in Journalism from UC Berkeley in 2021. Daniel has published multiple newspaper articles covering public health issues. His latest was a magazine cover story on pandemics and diseases that he co-wrote with Dr. Elena Conis, a historian of medicine, public health, and the environment.

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