Gastric Bypass

It was originally thought that the gastric bypass procedure produced weight loss mainly through malabsorption – i.e. calories from food and drink could not be absorbed across the bypassed section of small bowel.  This is not the case.

The gastric bypass does not result in significant calorie malabsorption but works by three other mechanisms.

First the very small pouch restricts the amount of food that can be eaten at any one time, which means fewer calories consumed.

Secondly – and most importantly – re-routing of the food stream and bypassing a segment of small bowel, results in major changes in a variety of appetite hormones, including ghrelin.  The net effect of these changes is a dramatic suppression of appetite.

Finally, patients undergoing gastric bypass report significant changes in food preferences, with a reduced interest in sweets, high fat foods and alcoholic drinks.

The average excess weight loss after a gastric bypass is around 70%.  In other words, if you were 100lbs overweight before surgery you can expect to lose around 70lbs.  As with the sleeve gastrectomy there is a tendency towards weight re-gain over time, but even at 10-years most patients will keep at least 50% of their excess weight off.  Furthermore, weight loss with the gastric bypass seems to be greater and more durable than with either the gastric band or the sleeve gastrectomy.

Gastric bypass has the strongest effect on high blood pressure, high cholesterol levels and other obesity-associated health problems.

It’s especially important to note the impact of the gastric bypass on Type 2 diabetes.  A recent study of 20,000 patients showed that showed that 84% of patients experienced complete reversal of their diabetes. Rapid improvement in blood sugar levels and reduction or elimination of diabetes medication is often seen in the immediate post-operative period – well before any significant weight loss has occurred.  This is due to the profound effects the bypass has on gut hormones, especially those involved in blood sugar regulation.  In fact, in those undergoing bypass, the need for diabetes medication declines to about 8% over time.  And – assuming weight loss in maintained – these benefits persist for life.

Although a gastric bypass is an invasive operation requiring quite significant changes to the anatomy of the bowel and stomach, in experienced hands it is a remarkably safe procedure; studies shows that 99.8% of patients survive the procedure.  In fact the risk of a gastric bypass (0.2%) is about the same as having your gallbladder removed (0.15%) and safer than a hip-replacement (0.29%) or a C-Section (0.4%).

The general risks of gastric bypass are the same as those with any major surgical procedure and include

• Excessive bleeding
• Infection

• Adverse reactions to anesthesia
• Blood clots
• Lung or breathing problems
• Leaks in your bowel/stomach
• Death (rare)

Longer term risks and complications of bypass surgery include:

• Dumping syndrome, causing diarrhea, nausea or vomiting
• Gallstones
• Hernias
• Low blood sugar (hypoglycemia)
• Vitamin and mineral deficiencies
• Bowel obstruction

Dumping syndrome is a condition that can develop after gastric bypass and also after sleeve gastrectomy.  It occurs when sugars move from the stomach into the bowel too quickly.

Most people with dumping syndrome develop signs and symptoms, such as abdominal cramps and diarrhea, 10 to 30 minutes after eating. Other people have symptoms one to three hours after eating, and still others have both early and late symptoms.  These include:

• Nausea
• Vomiting
• Abdominal cramps
• Diarrhea
• Flushing
• Dizziness, lightheadedness
• Rapid heart rate

Generally, you can help prevent dumping syndrome by changing your diet after surgery. Changes might include eating smaller meals and limiting high-sugar foods.

Although around 60-70% of gastric bypass patients develop some degree of dumping, in only around 5% does to become chronic and require specific treatment in the form of medication or (rarely) surgery.

Some patients even claim to like dumping because they regard it as a form of aversion therapy – to stay away from sweet things!

Although calories are generally absorbed as normal after a gastric bypass, vitamins and minerals are most certainly not.   So, it is absolutely essential for you to take regular (daily) vitamins and minerals after bypass surgery.  If you fail to do this, you are almost certain to run into serious health problems, such as anaemia, nerve damage and bone disease.

Key micronutrients include Vitamin B12, B1 (thiamine) and D, calcium, iron and zinc.

You will be given detailed information regarding vitamin and mineral supplements after surgery.