Patients who struggle with obesity and have failed in previous attempts to lose weight with non-surgical methods may be eligible for bariatric surgery, a group of procedures that facilitate weight loss. There are different types of bariatric surgery, either based on food volume restriction, which are procedures designed to physically limit the amount of food the stomach can hold, or malabsorption, which are used to shorten or bypass part of the small intestine, reducing the amount of calories and nutrients the body absorbs.

None of the surgeries directly cause weight loss, but they do help patients lose weight as they follow medical recommendations regarding lifestyle alterations, dieting and exercise. The goals are different for each patient and according to the type of surgery itself — all topics that should be discussed between physician and patient and taken into consideration prior to deciding which type of bariatric surgery to choose.

Average Weight Loss After Bariatric Surgery Depends On Type

Bariatric surgery is meant to restrict food intake that in turn leads to accelerated weight loss, and a medical team will discuss with the patient the most appropriate type of surgery. The four types of bariatric surgery — Roux-en-Y gastric bypass, laparoscopic adjustable gastric banding, sleeve gastrectomy and duodenal switch with biliopancreatic diversion — are all uniquely different and will produce different results. The American Society for Metabolic and Bariatric Surgery evaluated the advantages and disadvantages of each type of surgery.

Gastric bypass is the most common type of bariatric surgery and will result in a significant long-term weight loss between 60 and 80% of excess weight loss, with a typical maintenance of about 50% excess weight loss, but it is also a more complex procedure, which can result in longer hospital stays and greater complication rates. On the other hand, adjustable gastric banding induces an average of 40 to 50% percent of excess weight and it is the least invasive and a reversible surgery. However, some patients fail to lose at least 50% of excess body weight — typically due to a lack of patient compliance to the accompanying weight loss program.

Sleeve gastrectomy induces rapid and significant weight loss compared to the gastric bypass, leading to an average weight loss of about 50% of excess weight, but it is a non-reversible procedure with high potential for long-term vitamin deficiencies. Also, while rare, there are potentially fatal post-surgical side effects, such as gut leakage and sepsis — issues that are not present with a gastric band.  In addition, the duodenal switch with biliopancreatic diversion has a greater weight loss, between 60 and 70%, reduces the absorption of fat by 70 percent or more, is the most effective surgery against diabetes, and allows patients to eat meals nearly normal, but it also has higher complication rates and risk for mortality, requires a longer hospital stay, and has a greater potential to cause protein deficiencies and long-term deficiencies.

Factors That Impact Average Weight Loss After Bariatric Surgery

“Average” means that patients can achieve higher or lower percentages of weight loss following a bariatric surgery. While these procedures offer tools to help the body lose weight, patients must commit to a lifetime of healthy eating and regular exercise in order to achieve and maintain their goals. After being submitted to surgery, patients will start on a liquid diet and gradually transition to solid foods. Patients are usually accompanied by a dietitian in their weight loss journey and it is essential to follow a healthy diet and the medical team’s recommendations, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

Exercising may not be easy at first, but patients will have a personalized plan tailored by their physician to their needs and medical situation, while continuing to attend regular medical visits also helps during the process. In addition, the study “Psychological factors and weight loss in bariatric surgery” emphasizes the importance of psychological assessment before bariatric surgery and systematic follow-up to guarantee optimal weight loss and weight loss maintenance, as self-monitoring and cognitive behavioral programs could prevent weight regain.

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