Bariatric surgery

Bariatric surgery, often called metabolic or weight loss surgery, is a group of medical procedures. These surgeries help manage obesity and various related health conditions. They are most often used when diet and physical activity are not enough. For many, these procedures provide the most effective treatment for long-term weight loss. They do more than just change body size. They can also change how the body processes energy and signals hunger.

These surgeries work through several different biological mechanisms. Some procedures are restrictive, meaning they physically reduce the size of the stomach. This limits how much food a person can eat before feeling full. Other procedures are malabsorptive, which means they reduce nutrient absorption. This means the body takes in fewer calories from fats, proteins, and carbohydrates. Many surgeries also alter gut hormones. These hormones are chemical signals that control hunger and satiety, which is the feeling of being full. By changing these signals, the body may reach a new hormonal weight set point.

There are several distinct types of bariatric procedures. One common type is the sleeve gastrectomy, which creates a smaller, sleeve-shaped stomach. Another major type is the Roux-en-Y gastric bypass. This procedure creates a new path for food to travel through the digestive system. There is also the biliopancreatic diversion with a duodenal switch. This method often results in significant weight loss through both restriction and malabsorption. Other options include gastric banding, which is considered the least invasive method. Each type has different levels of efficacy and risk profiles.

Medical guidelines for who should receive surgery have changed over time. In 1991, the NIH Consensus Statement set the threshold at a BMI over 40. BMI, or Body Mass Index, is a measurement used to categorize weight. As research grew, these rules were updated. In October 2022, the ASMBS and IFSO revised the criteria. Now, adults with a BMI over 35 are candidates. Those with a BMI between 30 and 35 may qualify if they have metabolic syndrome. Guidelines also change for different populations. For example, Asians may be considered if their BMI is over 27.5.

Bariatric surgery offers significant health benefits backed by data. A 2021 meta-analysis showed a reduction in all-cause mortality for obese adults. For those with type 2 diabetes, median life expectancy increased by 9.3 years. For those without diabetes, the gain was 5.1 years. The surgery also helps manage chronic diseases. It can reduce the risk of type 2 diabetes by 61% to 77% depending on the condition. In many cases, 85% to 90% of people see their diabetes resolve. Furthermore, the overall cancer risk can decrease by 44%.

While the benefits are large, there are specific risks and contraindications. The risk of death following surgery is very low, at less than 1 in 1,000. However, doctors must check for conditions that make surgery unsafe. These include active cancer, severe heart failure, or pregnancy. People with certain gastrointestinal diseases, like Crohn's disease, may have limited options. Mental health is also a major factor in success. About half of surgery candidates may struggle with depression. Because of this, psychiatric screening is a critical part of the process.

The impact of surgery extends to many different body systems. It can improve cardiovascular health by reducing the risk of stroke and heart attack. For women, it can improve fertility and normalize menstrual cycles. It can even reduce the symptoms of polycystic ovary syndrome. However, it can also lead to new challenges, such as increased risks of preterm birth. For adolescents, research shows that surgery does not negatively impact growth or puberty. Ultimately, bariatric surgery is a complex tool used to reset the body's metabolic health.