What is Gastric Bypass Surgery?

Also known as the Roux-en-Y, RNY or standard gastric bypass, the procedure is one of the most popular weight loss surgeries performed in the world. Gastric bypass Surgery is designed to help you achieve weight loss and manage obesity related health conditions.

The procedure involves creating a pouch out of your stomach and joining it to your small bowel to circumvent part of the gut, restricting the amount of food you can eat and the number of calories you can absorb. It also alters your gut hormone levels, helping you to feel full earlier.

How does gastric bypass work?

Under general anesthesia, Dr Siva makes 5 small incisions, each measuring 5-12mm. Through one of these incisions, a laparoscope is inserted, complete with a miniature camera and light, providing an amplified view on a monitor. Dr Siva then creates a small pouch by skilfully stapling around the upper section of the stomach. This reduced-size stomach pouch is then directly linked to a segment of the small intestine, forming a bypass.

This rerouting of the digestive tract serves to restrict food intake and calorie absorption, aiding significant weight loss.

About Perth Obesity Solutions

Dr. Siva Sundararajan is a highly qualified Australian bariatric surgeon, leading our team’s expertise in gastric bypass surgery. With a Bachelor of Medicine, Bachelor of Surgery, Fellowship of the Royal Australasian College of Surgeons, and advanced bariatric fellowship training in Australia and Europe, his reputation as a trusted specialist in complex cases underscores his dedication to achieving successful and lasting weight loss outcomes for our patients.

Gastric Bypass Results

Weight-loss Expectations from Gastric Bypass Surgery

Within the first year following surgery, patients can typically anticipate losing between 70 and 80 percent of their excess weight.

Accordingly, someone about 170cm tall, with a BMI of 40 can anticipate losing 30–35 kg in the first year. This weight reduction usually happens swiftly in the first six months post-surgery, and over the following six months, weight loss happens more gradually.

3 months post-surgery

The first three months after gastric bypass surgery are when patients typically experience the most rapid weight loss, due to changes to the digestive system hormones, limiting intake and absorption of calories. On average, patients can expect to lose 10-15kgs, or 25-35% of their excess weight, during this time.


6 months post-surgery

The rate of weight loss may slow down after three months, but patients can still expect to lose up to 1kg per week for the next three months, resulting in a total of 45% of excess weight lost.


12 months post-surgery

By the 12-month mark, some patients may have reached their target weight, with 70-80% of excess weight lost. For those who have not yet reached their goal, it is important to stay focused and continue to work towards it.

Eligibility for Gastric Bypass Surgery

Eligibility requirements for gastric bypass surgery vary, but the surgery is recommended for individuals who have a body mass index (BMI) of 35 or higher, or a BMI of 30 or higher with at least one obesity-related comorbidity such as diabetes, high blood pressure, or sleep apnea.

Additionally, candidates for gastric bypass surgery should have attempted weight loss through diet and exercise and other non-surgical methods without success. They should be committed to making permanent lifestyle changes, including following a healthy diet and regular exercise regimen.

If you would like to find out more information and see whether a gastric bypass procedure is the right option for you, contact us today. Dr Siva can review your personal situation and help you make the best decision for your health journey.

Contact us to arrange your initial consultation.

Calculate Your BMI

Results: BMI =

Frequently Asked Questions

Am I eligible for a gastric bypass?

It’s very important to get medical advice from a specialist bariatric surgeon, however, you may be eligible for a gastric bypass if you meet the following criteria.

  • You have been diagnosed as a diabetic.
  • You’re taking daily medication for heartburn.
  • Your BMI (Body Mass Index) is higher than 35kg/m2.

If you would like to find out more information and see whether a gastric bypass procedure is the right option for you, get in touch with us today. Dr Siva can review your personal situation and help you make the best decision for your health journey.

Contact us to arrange your initial consultation.


Is gastric bypass safe?

Gastric bypass surgery is very safe for the majority of patients. Complications can occur in about 2-3% of procedures. These include leaks, internal hernias, dumping syndrome, ulcers, narrowing of the connections, clots in the legs, bowel blockages from internal scarring and bleeding.

There is a risk of internal hernias of about 2% and although the internal defects are closed, they can re-open after considerable weight loss.

Nutritional deficiencies can occur, multi-vitamin supplementation and follow up for these with blood tests are extremely important.

How much does gastric bypass surgery cost?

A gastric bypass procedure costs between $5,000 to $6,000, however, part of the operation cost is covered by your health fund and Medicare. 

There will be a gap payment that will vary depending on the type of bypass you need and any other procedures that need to be completed during your surgery. 

What should I expect after surgery?
  • Most patients will stay in hospital for 2-3 days
  • Nausea is the most common problem and regular anti-nausea medications are given

Day of surgery

Following surgery, you will wake up in the theatre recovery where the nurses will monitor you and keep you comfortable.
If necessary, a “patient controlled analgesia” pump will be connected to the drip in your arm to manage your pain. Most patient do not require this and it can be cumbersome to move around with the drip stand. This can slow down your recovery. However, it is also very important to get your pain under control so that you can get moving.

You can have sips of water and small tablets. Larger tablets will need to be crushed or broken.

Day 1
On the day after your surgery, you will need to sit out of bed much as possible and undertake deep breathing exercises every hour. An incentive spirometer may be provided. This device helps you exercise your lungs. The aim is to inhale and raise all three balls and hold them up for a second or two before exhaling. This allows the lungs to open up fully, reducing the risk of infection or fluid collecting there.

You should have white coloured stockings called TEDs (Thromboembolism Deterrent Stockings) and a device on your legs that simulates the work you calf muscles. You should be able to walk to the toilet and back without assistance and progress to walking longer distances within the ward.

Beyond Day 1

progress to thin bariatric fluids, walk around the ward. Patients are usually on thin bariatric fluids for 2 weeks, pureed diet for 2 weeks, soft diet for 1 week and solid foods thereafter. Tough meats such as beef or lamb should be avoided in the first 6 -8 weeks.


2 weeks post surgery
3 months post surgery
6 months post surgery (with blood tests)
1 year post surgery (with blood tests)
Yearly thereafter

How long does it take to recover from gastric bypass surgery?

Everyone is different and the amount of time it takes for you to recover from your surgery will depend on your level of health. In most cases, you will need to take about two weeks off before you can return to work. It’s important to follow our advice post-surgery to ensure you experience a smooth recovery.

What diet must be followed after roux en y surgery?

During your initial recovery, you will need to follow a post-surgery diet plan.

You will start with a liquid diet before progressing to pureed and softer foods. In most situations, you will be able to have a normal diet after a couple of months.

Once you have recovered, it’s important to maintain a healthy, balanced diet to get the best results from your procedure.

At Perth Obesity Solutions, we will guide you step by step to help you manage your diet at every stage.

What are the risks immediately following surgery?

Every surgical procedure comes with a certain level of risk. With a gastric bypass, there is arisk that you may experience the following post-surgery:

  • Bleeding or infection– less than 1% chance.
  • Leak from the join or staple lines – 2-4% chance.
  • Strictures or narrowing of the join – 5% chance.

There is also a risk of dumping syndrome. If you consume a large volume of refined carbohydrates or sugar, you may experience abdominal cramps, sweating and dizziness. This usually improves after about 3 months.

What are the long-term risks after having a gastric bypass procedure?

In the longer term, you may experience nutritional deficiencies. It is vital that you take your prescribed supplements to prevent this from occurring.

There is also a risk of weight regain, with 5-10% of patients regaining enough weight after 10 years to consider revision surgery.

Loose skin can form after a gastric bypass procedure. This varies between patients and can be reduced by engaging in exercises to strengthen your core.

In bypass, the stomach acid enters the small bowel directly without first being neutralised by pancreatic juices. This can irritate the small bowel and cause ulcers at the anastomosis. Taking anti-acid medications can minimise this risk.