• 23 JUN 14
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    How Gastric Bypass Surgery Changes the Brain’s Response to Food

    It has long been understood that gastric bypass, by altering the functionality of the stomach, is capable of helping patients to achieve weight loss in large quantities. Studies are now showing that there are additional benefits to patients of gastric bypass procedures beyond the obvious changes in digestion and metabolism. For example, according to a research study which was recently published in a journal called Gut, gastric bypass procedures are also capable of drastically changing how the brain responds to eating. What this means is not only does the surgical procedure alter the patients’ hunger by reducing it, but it may also change the patients’ drive to pleasure-eat.

    Gastric Bypass Surgery

    The primary mechanism for gastric bypass surgery is to re-route the digestive system, avoiding most of the stomach. What this means is that most of the patient’s undigested food is going to reach the intestine more quickly. There are other types of bariatric surgery which can cause significant weight loss, but these typically do not involve re-routing the digestive system, and so the same effect is not achieved. Still, weight loss surgery is considered to be the most effective treatment not only for obesity, but all related comorbidities as well. Over a period of 20 years, patients who undergo gastric bypass surgery tend to lose 25 percent of their body weight on average, as compared to 14 percent with gastric banding procedures. In the past researchers have noted that patients undergoing gastric bypass surgery begin to trend away from

    The Study

    The study has involved the use of functional magnetic resonance imaging or fMRI, a scanning technique which allows for the measurement of brain activity by detecting changes in the flow and levels of blood oxygen. Using this technology, scientists took a look at 61 women and men who had experienced weight loss using either gastric banding surgery or gastric bypass over a period of eight to nine months. The technology was also used to scan a control group of patients who had not received either operation. All of the three groups of individuals had similar body weight numbers.

    The study found that there were marked differences in how the brain responded to food in patients who had undergone gastric bypass, as compared to patients who underwent gastric banding surgery or no surgery at all. Patients who had experienced a gastric bypass procedure experienced less activity in the reward regions of their brain when they were shown pictures of food as compared to individuals who had experienced the gastric banding surgery.

    Results of the Study

    As compared to patients who had undergone no surgery, or who had undergone the gastric banding procedure, patients who had undergone the gastric bypass surgery showed the following differences:

    • The reward regions in their brain experienced less activity when they were being shown pictures of different types of food.
    • When they looked high-calorie foods, they rated them as being less appealing.
    • They rated these same high-calorie foods as being less appealing to eat.
    • They had healthier eating habits in general.
    • They tended to consume fewer grams of fat in their normal diet versus the other groups.

    Both groups of patients who underwent bariatric surgery, both the gastric bypass group and the gastric banding group, did experience reduced hunger as compared to the group that did not undergo surgery.

    Conclusive Evidence?

    This evidence shows that there may be a correlation between gastric bypass surgery and a change in how the brain thinks about food, but more research is going to be necessary to determine how much causation applies. Researchers have stated that they did not find specific conclusive evidence of what led to these specific changes, though they did note a number of specific differences in the metabolisms of the groups of patients which can lead to better understanding. For example, there are hormones in the gut known as GLP-1 and PYY, and these were higher in the group that underwent gastric bypass as compared to those who did not. These hormones are responsible for helping us feel full after we eat a meal. The same is true for levels of bile salts, something that we need to help with adequate digestion.

    The individual who led the study, Dr. Tony Goldstone, said that it is well established that patients having undergone gastric bypass surgery will lose more weight than those who undergo gastric banding. He believes that this is because there are different physical changes which are made during the gut during the course of the surgery, and that these changes are playing a role in our natural drive to eat for pleasure. Both of these procedures are capable of reducing a patient’s appetite and offering numerous other health benefits as well. One of the biggest improvements that patients experience is a resolution of diabetes type 2. Gastric bypass surgery, however, appears to be the more effective approach when it comes to weight loss, especially when you consider the profound impact that it appears to be having on how the brain responds to the concept of food.

    Future Implications

    According to Dr. Tony Goldstone, the research findings talked about here are putting emphasis on the fact that the different types of bariatric procedures can work in very different ways in order to influence the eating patterns of patients. This is going to have important implications when it comes to treating patients with obesity, and it may help to develop a much more personalized approach to choosing the right bariatric procedure for each individual patient. It is a known fact that people eat not only for sustenance, but also for rewarding and pleasure feelings that we receive when we consume foods we enjoy. By changing how the body perceives food and focusing purely on the health and sustenance facets of eating, we could potentially change the face of obesity in the future. Understanding how gastric bypass changes the way the brain responds to food will help researchers better understand the benefits of bariatric surgery.

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