Laparoscopic Gastric Bypass
Gastric Bypass is the most frequently performed bariatric (obesity) procedure worldwide (65% of operations).
The operation is truly a by-pass of the stomach. The stomach is by-passed so that food
eaten goes into a small gastric pouch and then into a loop of small bowel (the jejunum).
How Does it Work?
The gastric bypass assists in weight loss by the following 4 mechanisms:
- Satiety is induced by the small gastric pouch, and through the “switching off’ of the hormones that cause hunger. Most patients go many months before they have any recognisable hunger sensations.
- Over-eating is prevented by the small pouch. Too much food causes discomfort and vomiting. In some patients a ring can be put around the pouch to further prevent overeating (the Banded Bypass).
- The operation causes intolerance to sweets and high density carbohydrates (fatty, oily food) as the rapid presence of sugar or large volumes of carbohydrate in the small bowel leads to unpleasant symptoms called “dumping”.
- There is trivial malabsorption of fat as the food eaten is initially not mixed with bile and pancreatic juice. There is no protein or carbohydrate malabsorption.
- 85-90% of sufferers of type 2 diabetes have their diabetes completely resolved, often before they leave hospital. The mechanism for this is not known but it may be due to bypass of the duodenum and pancreas.
How effective is it?
The operation allows the average patient to lose 60 – 80% of their excess weight in 12-18 months. After this most patients re-gain some weight. This weight gain occurs for a variety of reasons such as poor compliance with diet and exercise and physiological adaptation of the body to the operation. At 5, 10 and 15 years the weight loss stabilises at approximately 50-70% of excess weight. Weight regain may be preventable through dietary compliance.
Approximately 5-15% of patients will not lose adequate weight with the operation (ie >50% excess weight). These patients cannot be reliably identified pre-operation but weight loss failure is very uncommon apart from in the super obese (BMI >50) who may still lose significant weight. More “aggressive” surgery is possible but leads to severe nutritional problems in some patients. Re-operations for “failure” can sometimes be difficult and may have variable success.
For most patients the operation will result in the average patient losing 60-80% of excess weight. This means they will still be a little overweight but will have lost enough weight to reduce their obesity related risk profile to that approximating the normal population.
Why is it popular?
- It produces massive and appropriate weight loss in most patients. Median weight loss at 12 months is 60-70% excess weight, with consequent reduction or complete resolution of complications of obesity such as diabetes, lipid abnormalities, sleep apnoea etc.
- The operation can be done at an acceptable mortality (0.5 – 0.01 %). Morbidity (significant post operative illness) is low and post-operative side effects and nutritional deficiencies are only rarely severe. B-12 and iron deficiencies are a predictable problem as the stomach is by-passed. Calcium supplementation may also be required because of the duodenal bypass and reduced amounts of food eaten post-operatively.
- World wide there is >15 years of experience with the operation with weight loss maintenance of approximately 50% of excess weight. There is little variation in results from hospital to hospital and country to country.
What is Life Like With a Gastric Bypass?
Patients get used to eating three small meals a day, usually 25% of previous serves. When going to a restaurant they can eat an entree sized meal and feel satisfied (while they watch their friends over-eat with an entree, main and dessert).
Sweets and fatty foods are poorly tolerated and best avoided. These foods will cause “dumping” due to the rapid presence of high osmolarity fluid in the small bowel. Symptoms are nausea, dizziness, palpitations, sweating and abdominal discomfort. To avoid dumping, high sugar and fat content foods should be avoided and food should be eaten dry and not mixed with fluids. Otherwise apart from a commitment to “healthy eating” no other foods are specifically banned. Snacking especially on junk foods is to be avoided as it will greatly negate the effects of the surgery.
Multivitamins and B-12 need to be taken by all. Menstruating females need iron supplements, post-menopausal women will need calcium (as well as some premenopausal women and some men). These requirements are life-long.
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