A peer-reviewed, evidence-based journal that promotes clinical development and metabolic insights in total bariatric patient care for the healthcare professional
18
Review
GASTRIC BANDING and the Fine Art of Eating
by PAUL O'BRIEN, MD 2011;8(9):18–21 ABSTRACT
The author reviews the physiology of eating and what the adjustable gastric band does to the function of the distal esophagus and upper stomach of the patient. The author also provides the "Eight Golden Rules" on proper eating habits for patients of laparoscopic adjustable gastric banding, including what, when, and how they should eat, in order to achieve optimal weight loss results.
KEY WORDS Laparoscopic adjustable gastric band, LAGB, gastric banding, eating and gastric band
Continued from page 1 and/or vomiting after LAGB.7–15
In
Burton's series of articles, he concluded that in LAGB, it is not the band that fails, but rather the patients who receive the band and, more importantly, the doctors who care for them.
Many years ago at the Centre for Obesity Research and Education (CORE), my colleagues and I developed the Green Zone chart, a conceptual way of identifying the optimal level of band restriction (Figure 1). When a patient is in the yellow zone, it is an indication that the band is too loose. When in the yellow zone, a patient may be eating too easily, feeling hungry, and not losing weight. When a patient is in the green zone, he or she does not feel hungry, is satisfied with small amounts of food, and is achieving weight loss or maintaining a satisfactory level of reduced weight. When a patient is in the the red zone, it is an indication that the band is too tight. The patient experiences reflux, heartburn, and vomiting. The range of food the patient in the red zone can eat after undergoing LAGB is limited and he or she may start to eat abnormally (so- called maladaptive eating), favoring softer, smoother foods like ice cream and chocolate. While in the red zone, patients will not lose weight as effectively and they may even gain weight.
Burton measured the pressure within the upper stomach beneath the band in numerous patients when they were in the green zone. He found the optimal pressure was typically 25 to 30mmHg. The art of adjustment is to find the level of fluid in the band that achieves that pressure range. That level of pressure generates a background sense of satiety that
persists throughout the day. The patient, when correctly adjusted, normally will not feel hungry upon waking in the morning, and throughout the day should feel much less hungry than he or she did before band placement. In my experience, it is common for LAGB patients to have no feeling of hunger in the morning. Then, during the day, a modest level of hunger will develop, which a small meal should satisfy.
One of the key lessons learned
from Burton's studies was that each bite of food should pass across the band completely before another bite is swallowed. There is no pouch or small stomach above the band and there should never be food sitting there waiting.
The esophagus is a powerful muscular organ that typically generates pressures of 100 to 150mmHg, but it is capable of generating pressures above 200mmHg. Esophageal peristalsis squeezes the bite of food down toward the band and then progressively squeezes that bite across the band. Each bite must be squeezed across the band before the next bite starts to arrive. Figure 2 shows a bite in transit across the band.
A single bite of food, chewed well until it is mush, will move down the esophagus by peristalsis. At the level of the band, the esophageal peristalsis will squeeze that bolus of food across the band. It takes multiple squeezes (usually 2–6 squeezes or peristaltic waves) to get that bite of food across in a patient with a well-adjusted band (Figure 2). Those squeezes generate a feeling of not being hungry and stimulate a message that passes to the hypothalamus to indicate that no more food is needed. If a single bite of food is able to generate between two and six waves of signal, a meal of 20 bites
may generate 100 or more signals. This is enough to satisfy a person and is enough to signal him or her to stop eating. We recognize two terms for appetite control, satiety and satiation. Satiety refers to the background control of hunger that is present throughout the day regardless of eating. In the LAGB patient, satiety is generated by the band exerting a constant compression on the cardia. Satiation is the early control of hunger that comes with eating. In the LAGB patient, satiation is generated by the squeezing of the bolus of food across the band during a meal. Each squeeze adds to the satiation signal. There are sensors in the cardia of the stomach that detect this squeezing. The exact nature of these sensors is still to be confirmed but they must be either hormonal or neural. We know that satiety and satiation are not mediated by one of the hormones currently known to arise from the upper stomach.16 Ghrelin is a hormone that stimulates appetite. A number of hormones that can be derived from the cardia of the stomach are known to reduce appetite. None of these hormones are found to be raised in the basal state after gastric banding and none can be shown to rise significantly after each meal.16 Vagal afferents are plentiful in the cardia, and one group of afferents has a particular structure that lends itself to recognizing the compression of the gastric wall associated with squeezing of the bite of food across the band. In
my opinion, the intraganglionic laminar endings, better known as IGLEs, are the most likely candidate as mediator of the background of satiety throughout the day and the early satiation after a meal. The IGLEs lie attached to the sheath of the myenteric ganglia and are known to detect tension within the wall of the stomach. They are low-threshold and slowly adapting sensors and therefore are optimal for detecting continued compression of cardia of the stomach over a 24-hour period. The several squeezes that go with the transit of each bite stimulate the IGLEs further. The signal passes to the arcuate nucleus of the hypothalamus and the drive to eat is reduced. The lower esophageal contractile segment. Burton developed the concept of the lower esophageal contractile segment (LECS). It is made up of four parts: the esophagus, the lower esophageal sphincter, the proximal stomach (including the 1cm or so above the band and the 2cm of stomach behind the band), and the band itself (Figure 3).
As the esophagus squeezes the bolus of food down toward the band, the lower esophageal sphincter relaxes as this peristaltic wave approaches. It then generates an after- contraction, which can maintain some of the pressure of the peristaltic wave as a part of the food bolus is squeezed into that small segment of upper stomach. The upper stomach, including the area under the band, is sensitive to these pressures. It
Bariatric Times • September 2011
FIGURE 1. The Green Zone chart. Copyright © CORE
Bariatric T
imes.