Gastric Bypass Surgery - Macquarie Weight Loss and Surgical Services

Gastric Bypass Surgery

  • Home
  • Gastric Bypass Surgery

What is Gastric Bypass Surgery?

The gastric bypass operation is a highly effective procedure. It helps overweight patients to achieve a substantial weight loss. To help you understand your operation, it may be useful to have some knowledge of the digestive system.

Understanding Digestion

Food is taken in through the mouth and passes through the food pipe (oesophagus) into the stomach, where it is broken down into a semi-solid form. After several hours food continues into the small bowel, which is a long, coiled tube-like organ where further digestion and absorption of nutrients takes place. What remains then continues into the large bowel and eventually will be passed from the body as faeces

Is a gastric bypass for me?

The gastric bypass works best for people where large portion sizes and snacking
are contributing to their weight.

How does a laparoscopic gastric bypass operation work?

The word ‘laparoscopic’ means that the procedure is done through 5-6 very small cuts instead of one large cut on your abdomen. It is referred to as keyhole surgery. Sometimes, the operation cannot be done via keyhole, and a larger incision has to be made. If this happens, you may have more discomfort after the operation. You will need to stay in hospital longer and it may be longer before you can return to normal activities.

This procedure works by:

  • Making the stomach smaller, by placing staples across the upper stomach to form a small pouch, this is approximately the size of an egg cup.
  • A loop of bowel is also brought up to the new pouch to make a new stomach exit. This means that the amount of food that you will be able to eat, will be much smaller and you will feel full more quickly. Also, the length of small bowel that the food is passing through is greatly reduced, so fewer calories are absorbed. This is therefore a restrictive and a malabsorptive procedure. These changes may also cause something known as ‘dumping’, which is a result of eating sweet food such as chocolate, jam and fruit juice. This may cause a feeling of dizziness and nausea and sometimes diarrhoea. It will therefore help you to stop eating foods with high sugar content. You may also experience intolerance to fat which may cause diarrhoea. There is no point considering this procedure unless you are fully committed to following the dietary and lifestyle advice provided.

What diet will I have to follow once I have had the operation?

Remember that portions will be much smaller and food will have to be liquid consistency for the first 2 to 3 weeks and then pureed in the early stages after your operation. Initially, portion sizes will be two to three tablespoons of smooth pureed food per meal. Eating more than this, may make you vomit. You will not be able to take food and fluid together as this will overfill your new stomach and make you sick. You will need to wait 30 minutes before or after a meal to drink fluids. From about four to five months after your operation, you should be able to manage up to a tea-plate sized portion of normal textured food for each meal. In addition to the smaller portion sizes, it is likely that there will be some foods that you will be unable to manage in the long term.

These include:

  • white bread
  • pizza
  • boiled rice
  • pasta
  • meat
  • steak
  • nuts
  • fibrous fruits and vegetables such as oranges and pineapple, green beans and mushrooms

You may vomit if:

  • you eat too much
  • choose the incorrect texture of food
  • take food and fluid together or
  • eat too quickly.

The diet may appear to be limited to begin with, however patients who have had the operation have reported that they become more confident in trying different foods after the first 3-9 months following the operation.

What are the benefits of having a gastric bypass?

This operation will help you to achieve effective, long term weight loss.

Reduces health related problems:

  • Type 2 Diabetes
  • Osteoarthritis
  • Hypertension (high blood pressure)
  • Coronary heart disease
  • High cholesterol level

Have more questions about Gastric Bypass Surgery?

We have answered a lot of questions that our patients have - click to read more
Click Here

What are the risks, consequences and alternatives associated with having a gastric bypass?

Most people get through their operation with few problems, however in some cases there may be difficulties. As with any operation, there is a risk of serious complications such as heart attack or blood clot. Extremely rarely, there is a risk of not surviving due to problems related to the operation.

Specific risks associated with the gastric bypass operation include:

  • A breakdown in the joins between your new stomach and bowel.
  • A blockage or a narrowing in the joins between your stomach and bowel.
  • A hernia, which occurs when your bowel pushes through a weakness in the abdominal wall.
  • Wound site infection.
  • Nutritional deficiencies such as Vitamin B12, iron and calcium.


These risks are small but it is important that you are aware of them and that you have all the information you need before agreeing to have the operation. The gastric bypass is both a restrictive and malabsorptive procedure. There are other types of operations available, which work in a slightly different way, also detailed in this booklet. There is always the option of not receiving any treatment at all. The consequences of not receiving any treatment are:

  • Further weight gain
  • Shortened life span
  • Increase in obesity related diseases (as listed in the benefits above)
  • Low self esteem/depression.

Roux-en-Y Gastric Bypass

RYGB restricts food intake. RYGB also decreases how food is absorbed. Food intake is limited by a small pouch that is similar in size to the pouch created with AGB. Also, sending food directly from the pouch into the small intestine affects how the digestive tract absorbs food. The food is absorbed differently because the stomach, duodenum, and upper intestine no longer have contact with food.

One Anastomoses gastric bypass (Omega loop)

The One Anastomoses Gastric Bypass (OAGB) or mini-gastric bypass is quicker, technically easier and carries a lower complication rate (3%) compared to traditional gastric bypass surgery.

The mini-gastric bypass procedure is restrictive and malabsorptive. This means that the procedure reduces the size of your stomach, restricting the amount you can eat. The procedure also reduces absorption of food by bypassing up to 6 feet of intestines.


The stomach is divided with a laparoscopic stapler. Most of the stomach is no longer attached to the oesophagus. Your new stomach is much smaller and shaped like a small tube.

Between 2 to 7 feet of intestines are bypassed. The surgeon will attach the remainder of the intestines to the new stomach. Food now flows into your small tube-like stomach and then bypasses between 2 to 7 feet of intestines where it resumes the normal digestive process .

Recent studies show that it does reduce operating time (by 50 minutes), may lead to similar weight loss (some studies show that mini-gastric bypass may actually produce more weight loss), and reduce overall complication rates compared to gastric bypass surgery.