Over the past 20 years, mechanistic research has established important biological concepts explaining how gastric bypass works. Briefly, the surgery works in two ways as it involves a two-step procedure in which the stomach is stapled to create a very small gastric pouch and the intestines are rerouted to connect with the new smaller pouch. The surgery reduces the size of the stomach and reroutes a substantial part of the intestine. The result is reduced nutrient absorption as the ingested substances skip a large part of the intestine where nutrient absorption mainly occurs. Simplistically, the outcome of this intervention is fewer nutrient requirements because calorie-demanding nutrients do not get absorbed.

More recent research has shown that gastric bypass also induces a dramatic change in hormonal and metabolic function. Hormones are signaling molecules that influence metabolism and appetite. Four months after the surgery, hormonal changes are conserved in weight loss. However, largely calorie-wasting hormones are increasing, rapidly redirecting nutrients to lesser-used fat stores, facilitating energy to be redirected mostly to fuel from stored body fat to substitute for fewer ingested calories. Long after surgery, these hormones are contributing to amplifying increased fat loss and improved weight maintenance. Furthermore, intestinal bacteria and viruses have emerged as an interesting area of research that may explain post-surgical weight changes. Overall, we simultaneously change several biological reactions and effects through the surgery, and these changes are likely to have a great combined effect with only modest effects in each tissue or organ

Benefits of Gastric Bypass Surgery

The major benefit of gastric bypass is significant weight loss. Patients start losing weight soon after the surgery and, with a permanent change in their diet, can achieve and maintain the loss of greater than 50% of their original weight. Additionally, losing weight results in an improvement of almost all obesity comorbidities. Some diseases can resolve almost immediately with surgery before there is a marked decrease in total body weight. Patients who continue to lose weight after the first year continue to shed their medical problems, even if they were not resolved during the immediate postoperative period, as they result largely from carrying around the excess body fat. Also, if a patient does develop an obesity-related problem, being at a lower weight will make its management significantly easier whether the treatment is nonsurgical or surgical. Furthermore, patients experience an improvement in their psychological health and quality of life. They begin to feel better not just emotionally, but also with regard to everyday activities and physical functioning. This improvement in physical functioning is largely secondary to a decrease in body weight. After surgery, many are excited to be able to exercise, ride bicycles, walk, shop, and perform other activities that were once too difficult due to being overweight.

Many people would agree that social and emotional changes are perhaps the most desirable advantages of having the surgery. Many report unexpectedly high levels of satisfaction after the operation. Many people report completely changing the way they see the world and the way the world sees them. Other patients report relief at being more physically active, from eating not because they were hungry but for recreation. Some are the grateful recipients of improvements in health that they thought were lost to them some time ago. The biggest advantage of weight loss surgery is the long-term improvement in your overall quality of life with a sustained weight loss. It is satisfying to watch as you reintegrate back into society and participate in all the activities that require unrestricted mobility. Until that time, you cannot even fathom what a joy it is to live a life unchained by the burden of obesity. But, as stated previously, these rapid advantages do come with the risk of the surgery, and too many different types of operations have developed alternative disadvantages.

Risks and Complications Associated with Gastric Bypass Surgery

Gastric bypass surgery, like any other surgery, carries some inherent risks as complications can arise during surgery and in the postoperative period. While the surgery is minimally invasive and completed with a laparoscope, there is a surgical risk associated with anesthesia, bleeding, and infections, which can occur within the first month following surgery. Long-term complications such as nutritional deficiencies, dumping syndrome, an overwhelming and sometimes life-threatening reaction to sugars and carbohydrates that can cause severe cramps, diarrhea, sweating, headaches, anxiety, and rapid heartbeat, and bowel obstruction due to scar tissue formation can last beyond the first year following the procedure.

Psychologically, major weight-loss surgery is a difficult and unpleasant procedure, and it can result in anxiety, mood swings, and even the need for psychiatric counseling. Risks may be reduced with proper evaluation and patient selection, as well as careful patient and family counseling. The risks should be taken into account while considering the potential benefits. Risks can be minimized by adhering to an appropriate diet and attending follow-up appointments.

Gastric bypass surgery, like any other surgery, carries some inherent risks. Systemic complications like pneumonia, clots in the leg and lung, heart attack, and withdrawal from significant preoperative medications are heightened when surgery is combined with anesthesia. Postoperative bleeding occurs in 1-2% of cases and might necessitate blood transfusions and a second surgery. A significant number of wounds are covered with skin glue that later falls off. About 5% of wounds develop infections as a result. Wounds may tear apart; however, the use of a smaller incision and a longer period of time to remove stitches decreases this possibility. Another significant postoperative risk is a leak at the gastro-jejunal anastomosis, where the roux limb is connected to the stomach. The chance of such a leak happening is less than 1%, and the majority of leaks occur before the patient is discharged from the hospital. Because this is an unusual occurrence, it results in a prolonged postoperative hospital stay, the insertion of a belly tube through the skin to drain the leaked fluid, and sometimes another medical procedure. If a leak is discovered later, symptoms may include fever, increased pain, or drainage, and the patient may have to go to the emergency room for a check-up.

Conclusion and Future Directions

Gastric bypass is one of the most effective treatment options for obesity, capable of inducing weight loss, reducing comorbidities, and improving quality of life. It achieves these effects through positive changes in appetite and weight control, including reduced hunger, greater fullness, and a renewed sensitivity to the rewarding effects of eating smaller meals that ultimately make it easier for people to decrease calorie intake and maintain lower body weight. However, the tremendous benefits of surgery are also attended by significant potential risks, such as surgical complications, the emergence of anxiety, depression, or substance use disorders, and nutritional deficiencies. Many of these negative and even life-threatening consequences are caused by post-surgical nonadherence to dietary guidelines related to the need for smaller meal sizes, reduced calorie intake, and careful supplementation with vitamins and minerals. Surgical procedures target a wide range of homeostatically driven and reward-driven appetite and weight control functions, so the nuances among them will continue to evolve as our understanding of these mechanisms unfolds.

Prompted by the initial success of gastric bypass surgery and improvements in surgical technique and patient care, surgical procedures for the treatment of obesity continue to evolve. The full potential of surgery, in combination with strategies for increasing patient adherence to post-surgical dietary and activity guidelines, remains to be determined. Ongoing research will help to determine which patients are most likely to benefit from which surgical procedures and which kind of pre-surgical evaluation affords the greatest predictive power. The development of noninvasive alternatives to temporary or permanent neuroanatomical or chemosensory rerouting may make accommodations to the unique taste and meal preferences of a patient more effective than any of the surgical options currently available. Patient education and support interventions delivered pre- and post-operatively will ensure that patients are well equipped to relearn healthy eating and exercise habits, distinguish appetitive need from reward craving, and pursue the emotional, psychological, or social rewards they value most in ways other than eating. A better understanding of the individual variability in response to surgery will also help to guide the most appropriate treatment options. It is a testament to the power of neurobiology that these complex behaviors can be similarly engaged to therapeutic effect noninvasively in most cases. As our knowledge of neurobiology widens and deepens, these noninvasive solutions will become increasingly powerful tools in the mitigation of excess weight and its downstream diseases. Ongoing neuroscientific inquiry and technological creativity will continue to provide minimally invasive or non-invasive solutions which, when combined with ongoing improvement in lifestyle and behavior therapies, will continue to erode the need for bariatric surgery in future generations.