In this section we refer to the Roux-en-Y gastric bypass (RNY) which is by far the most common of the many variations of gastric bypass operation that is performed in the world today.
- A small stomach pouch is created which reduces the amount of food you can eat (restriction).
- Food leaves the new stomach pouch through a new opening and bypasses the rest of the stomach and much of your small intestine. This means that less calories are absorbed as the food passes through your body (malabsorption).
- If you eat a large quantity of sugar, the body responds by overproducing insulin which makes you feel light–headed and queasy. This acts as a deterrent from over–eating the wrong types of food (commondly referred to as dumping syndrome).
Because the weight loss following a gastric bypass is generally greater than that achieved with a gastric band, your surgeon may recommend this option to patients with a BMI greater than 50 kg/m², although this is not automatically the case as matching the surgery to the individual patient is most important.
There are a number of variations of gastric bypass operation but the most popular one conducted in the UK is called a Roux–en–Y gastric bypass (RNY), after the French surgeon who developed the technique. At surgery, the top section of the stomach is divided off by a line of staples, creating a small 'pouch' stomach. A new exit from this pouch is made into a 'Y' loop from the small intestine so that food bypasses your old stomach and part (about 100-150cm) of the small intestine. The size of stomach pouch and the length of small intestine that is bypassed are carefully calculated to ensure that you will be able to eat enough for your body's needs at normal weight. Your weight will fall till it gets near this point, and then stabilise.
How much weight will you lose after a gastric bypass?
Studies show that on average, people lose between 66–75% of their excess weight in the two years after gastric bypass surgery. The really good news is that long before you reach that goal, you will start to feel the benefits, especially if you also have any of the obesity–related diseases such as diabetes, heart disease or high blood pressure. You will also have a much greater capacity for physical activity and more self–confidence.
If you are motivated to follow the eating plan, increase your exercise, keep follow up appointments with the healthcare team and keep in touch with a patient support group, you are more likely to achieve a greater weight loss.
The gastric bypass operation
Most surgeons do this operation by laparoscopic (keyhole) surgery in the UK. You will be admitted to hospital either the night before, or the morning of your surgery and the usual length of hospital stay is 2-5 nights afterwards. Through a series of small incisions across your upper abdomen he/she will use laparoscopic instruments and be guided by a special telescope with a camera. The surgery takes between 1-3 hours usually. Some people who are very obese, or who have had previous abdominal surgery may not be able to have this operation done laparoscopically and it will be done via a normal 'open' incision in these circumstances. If this happens, you will take a little longer to recover from the bigger incision, but it should not adversely affect your subsequent weight loss progress.
People who lose weight rapidly are more prone to developing gallstones, and to save the potential need for further surgery, some surgeons will propose that they remove your gallbladder at the same time.
The operation will cause you some pain and discomfort, and this will be managed with pain relief medication. Initially you will have an intravenous drip but you will be able to start drinking sips of water quite soon after the operation. You will also be encouraged to get up out of bed the same day as your operation.
Some surgeons perform a special X–ray 2–4 days after the operation to check that the stitches and staples joining the pouch and intestine are healing well and there are no leaks. Following this, you are generally allowed to start drinking freely.
4–6 weeks after the laparoscopic bypass operation you will be back to normal activities, already seeing some weight loss. You will progress from your pureed diet to solid food step by step, with careful supervision from the surgeon and dietitian.
Risks and Side Effects
Fortunately, complications are rare but it is important you learn about the potential problems before you decide to proceed with the surgery.
Firstly, being obese makes any surgery more risky. Anaesthetics are more difficult, and obesity related diseases that you may have can add further complications. Statistics show the death rate associated with gastric bypass surgery to be about 1 in 200 operations. The most common cause of death is a blood clot in the lung (pulmonary embolism) or problems arising from a leak in one of the joins made during the surgery. This may sound quite high and you need to weigh up for yourself the risk of dying during surgery against the risk of dying from your obesity or the effects of it on your health.
The greatest hazard after gastric bypass surgery is developing a leak from the join between the stomach and the small intestine. If it were to occur, a second operation would be required immediately. Occasionally you may develop other complications at the time of operation such as an infection in your lungs, in the stomach or in one of your wounds, which may delay your recovery.
Doing the surgery laparoscopically helps to reduce the risk of complications, and the team who manage your surgery and anaesthetic are specially trained in the treatment of obese patients. They will monitor you closely in the period immediately following your surgery, and take a range of measures to prevent complications from arising, including giving you medication to prevent vomiting or developing a blood clot and getting you up and about soon after the operation.
Other long term risks include dilation of the pouch or the development of a hernia and these can be repaired surgically. Because of the malabsorption component of this surgery, you may not absorb sufficient minerals and nutrients from your food for your body's needs. Deficiencies can generally be prevented by taking a daily multivitamin supplement and regular monitoring.
Despite the best care and attention, a small proportion of patients will fail to lose more than 25% of their excess weight with a gastric bypass operation and further revisions to it may be necessary.
Medical Follow Up
A multidisciplinary healthcare team, headed by your surgeon and comprising a mix of professionals such as other physicians, dietitians, nurses, exercise specialists and a psychologist, will work together to help you get the best results from your gastric bypass surgery. This means resolution or improvement in obesity–related diseases as well as weight loss.
You will be required to take vitamin and mineral supplements for the rest of your life and your blood will be tested every 6 months or so to ensure you are not developing any deficiencies in these.
Even when you have reached your weight loss goal, the healthcare team will want you to attend annual appointments so that they can check that your bypass is functioning as it should.