Bariatric (weight loss) surgery – FAQ

What is weight loss surgery? 

Bariatric surgery, or weight loss surgery, refers to the operations designed to reduce weight by reducing your appetite or helping restrict the amount you are able to eat in one meal.

The term does not include procedures for surgical removal of body fat such as liposuction or tummy tuck.  

Studies show weight loss surgery can result in significant long-term loss of weight, remission of type 2 diabetes, improvement in heart health, and a reduced risk of cancer and premature death.


What types of weight-loss surgeries are available?

The two most commonly performed types of weight loss surgery are:

  • Gastric bypass – your digestive system is re-routed so that swallowed food exits the oesophagus, bypassing most of the stomach, and directly enters midpoint of the intestine.
  • Sleeve gastrectomy – where about 80% of the stomach is removed and only a thin cylinder of stomach tissue remains.

Both operations result in a feeling of fullness after eating a small amount of food. Up until recently, it was assumed that weight loss surgery worked solely by mechanically restricting the amount of food you can eat. However, it is now known that following bariatric surgery, changes in the balance of our gut hormone make us feel less hungry, reducing our desire to eat.

Both operations are usually performed laparoscopically (keyhole surgery) which will help you get up and about and back to normal as soon as possible after surgery

There are other surgical techniques that may be recommended in certain circumstances.

The type of weight loss surgery you have will depend on your circumstances, including how overweight you are and any other health problems you have.


How do I know if I am eligible for weight loss surgery? 

Weight loss surgery is available to treat people with potentially life-threatening obesity when other treatments haven’t worked.

The most widely used method of seeing if you’re a healthy weight is to calculate your BMI. This is your weight in kilograms divided by your height in metres squared. 

You may qualify for surgery if your: 

  • BMI is 30-35kg/m2 and you have type 2 diabetes mellitus which is not well controlled
  • BMI is 35 -39kg/m2 and you have at least 1 medical condition related to your weight
  • BMI is 40kg/m2 or above 


What are the benefits of weight loss surgery?

Studies on more than 20,000 patients showed that in patients who had lost weight following bariatric surgery:

  • 50- 84% experienced complete remission of their type 2 diabetes
  • 70-90% had an improvement or remission of sleep apnoea
  • 40-68% saw an improvement or remission of high blood pressure
  • 25-40% reduction in the risk of death from obesity-related diseases (particularly heart disease and cancer)
  • There are also improvements in other obesity-related diseases such as fatty liver disease, asthma and polycystic ovary syndrome


What are the risks of weight loss surgery?

Weight loss surgery is a major operation that may lead to short-term and long-term health complications. The risks and complications vary according to the type of surgical procedure you choose to have and often depend on your age, level of excess weight, other existing health conditions and how well you manage your health and your lifestyle.

Before being considered for surgery you should have a comprehensive medical as well as psychological assessment to ensure that surgery is the right choice for you.

Weight loss surgery is carried out under general anaesthetic. Serious complications with general anaesthetics are rare but can be more likely when you are overweight.

The death rate is about 3 /1000 and approximately 2-5% of patients develop a complication within the first month of surgery.


How much weight will I lose? Will the weight loss be quick?

The amount of weight you lose and how long it takes depends on which surgery you have and how strictly you follow the diet recommended by your physician.

Your weight loss will also depend on how much excess weight you carry.

In reality, most patients lose between 40 to 70% of their excess weight but this can vary from person to person. That is 40-70% of the extra weight you are carrying over and above your ideal weight for your height. You may lose weight more rapidly in the first 3-6 months, then it tends to slow down, though the weight loss often continues for up to 18 months.


Do I need to follow a special diet before and after surgery?


It is recommended that patients follow a very low-calorie diet for two weeks before surgery. This diet is low in fat, carbohydrate and sugars. By following the strict diet your body reduces its glycogen stores (glycogen is a form of sugar stored in the liver and muscles) which in turn shrinks the liver. This allows the surgeons to have good access to the stomach that lies behind the liver. It is important to note that the liver can replace its stores very quickly. A single carbohydrate-rich meal shortly before your operation can undo all your good efforts and lead to difficulties during surgery. It is very important to follow this diet because if your liver is not sufficiently reduced, the surgery may be delayed or cancelled.


There is a special diet to follow after your surgery that helps to heal your stomach. You will progress from fluids to solid foods over a period of four weeks. It is very important that you do not overeat following the surgery when the stomach is healing.

Weight loss surgery provides you with an excellent tool for managing your weight but you have to make it work for you. If you are committed to maintaining a high-quality diet and changing your lifestyle for the better you will achieve the desired results as you will be eating less without feeling hungry.


The overall success of the procedure will depend on your choice of foods, how much you eat and how often. Although it will restrict how much you can eat in one sitting, surgery alone will not change your eating habits, neither will it influence the type of foods you ultimately consume.


Why is protein intake important for my body?

Protein is important for wound healing, for preserving your muscle tissue during the weight loss phase and also for hair health. Protein also keeps you feeling fuller for longer and may help fight off food cravings. All your meals should include protein. Your dietician will help you with a daily meal plan so that all your nutritional needs are met. 


Will I have to take vitamins and minerals?

Yes, but the amount and type you need depend on which operation you have had. With a sleeve gastrectomy, we recommend you take a complete multivitamin and mineral daily for life. With the gastric bypass, vitamins and minerals from food, in particular iron,  it’s in B12 and calcium, are not well absorbed so you will need to take extra supplements to correct these specific deficiencies.


Nutritional supplements do not replace the need for a nutritionally balanced diet. They simply help prevent deficiency and restore nutrients you may be lacking as a result of your small dietary intake.


Will I lose my hair?

Unfortunately, hair loss after bariatric surgery is common although this is not permanent and the growth returns back to normal after approximately nine months. There are a number of reasons why you may lose hair but it is generally the result of rapid weight loss or low nutritional status. Hair loss peaks around three to five months after surgery. Good protein intake and vitamin replacement will help reduce hair loss.


Do some people regain weight after surgery?

As many as 30% of people may regain some weight or fail to lose as much as expected. There is no amount of weight loss that is guaranteed. Long-term sustained weight loss and improvement in obesity related health conditions will only occur with healthy eating and regular exercise. Bariatric surgery is only a tool that makes these lifestyle changes sustainable.


Will I have excess skin after I lose weight?

After weight loss surgery, most people who have been overweight for many years are left with some excess skin. This varies from person to person and the main problem areas tend to be the tummy, arms and thighs. How much excess skin you get depends on your age, gender, activity level and how overweight you were to begin with. 


Should I exercise after weight loss surgery?

Regular exercise is extremely important for maintaining your weight loss. You should wait at least six weeks after your surgery before engaging in vigorous activity. When you lose weight you will also lose some muscle. Regular exercise helps preserve muscle and minimise excess skin. Aim for 150 minutes of moderate-intensity exercise a week.


Is the procedure reversible?

A sleeve gastrectomy is irreversible. Gastric bypass surgery is technically reversible, but it is only considered if there is a clear medical reason. Reversal of the procedures carries more risk than the initial procedure and may result in weight regain


The decision to undergo weight loss surgery is usually for life and should be considered very carefully.



It is recommended that you wait at least 12 months after your weight loss surgery before trying to conceive. This is because while you are experiencing rapid weight loss you are at risk of developing nutritional deficiencies. Certain vitamins and minerals are required for a healthy pregnancy and it is important that key nutrients are available from conception and throughout pregnancy

A gastric bypass can reduce the effectiveness of the oral contraceptive pill. As a result, there is a greater chance you may conceive so you should take precautions during the first twelve months following the procedure. Keep in mind that considerable weight loss can improve fertility so even women who have trouble conceiving are advised to take precautions. If you do fall pregnant, it is important to let your doctor know so that you can be monitored closely.



We advise that you stop smoking at least eight weeks prior to surgery to reduce the risk of any complications. Smoking can reduce blood supply to the healing tissue and slow down wound healing. It may also increase the risk of post-operative blood clots, deep vein thrombosis and postoperative chest infections. Finally, smoking can increase the risk of stomach ulcers in the long term after bariatric surgery.


By Dr Mohgah Elshiekh