Lifestyle change – diet


A new diet plan and developing good eating habits

This blog provides free general information for anyone who is seeking to understand more about diet and eating habits before and after bariatric surgery, not intended as a medical consult. Please seek appropriate medical and allied health advice for individual assessment and management.


The crucial learning points are:

  • Recognizing that bariatric surgery alone is not enough, this needs to be accompanied by a permamnet lifestyle change and behaviour modification.
  • Be aware of the differences between good eating habits versus an eating disorder or maladapative eating behaviour.
  • Understand that poor eating habits whether it is psychological or physiological, are often related to inferior weight loss results, nutritional deficiencies and psychological distress.
  • Seek help from a dietician and a psychologist when underlying behavioural issues are unearthed will be beneficial after bariatric surgery.




Pre operative diet change

Ideally the diet change would have been commenced in the pre-operative period. In the 2 weeks leading up to surgery, patients are advised to be on a very low calorie diet (VLCD), consisting of 800 calories a day and various commercial preparations are available for this purpose. The common ones are Optifast, Optislim, Tony Ferguson or Terry White, to provide the recommended daily intake of protein, vitamins and minerals.

The most important aim of the VLCD is to decrease the size of the fatty liver (by reducing caloric intake and hence the stores of glycogen and lipid) as well as the visceral adipose tissue depots, enabling better visualization and laparoscopic access to the upper stomach. This will lessen the technical difficulties, reduce the operating time, helps facilitate a better outcome (by producing the optimal size and well shape gastric sleeve) and reduce intra-operative complications.

Some studies have also shown that the amount of pre-operative weight loss is significantly correlated with the post-operative weight loss outcomes, perhaps an indirect reflection on patient compliance and motivation. Furthermore the 2 weeks of VLCD helps patient to mentally and physically prepare for what to expect in the post op period, especially in the first 2 weeks where only oral fluids is allowed. Without any solid meals, the VLCD will provide the essential protein, nutrients and vitamins.

On average a pre-operative weight loss of 5% body weight is recommended and is realistically achievable. On the day of surgery patients often reported feeling better already in both the physical sense and personal confidence level, excited to proceed with the surgery and their next phase of weight loss.

However the patients are less enthusiastic about the taste or enjoyment of the VLCD.




Post operative eating habits

Please refer to the section on “Diet and exercise after surgery ” about food portions and food choices. This section focuses on good eating habits.


It is important to be aware of the wrong eating habits after surgery in order to prevent stretching of the remnant stomach leading to loss of restriction, satiety and early weight regain.

  • Binge eating is defined as eating a large amount of food within a 2-hour period.
  • Grazing is defined as eating smaller amounts of food over a long period of time (throughout the day).
  • Uncontrolled eating has been found to be associated with minimal weight loss result and psychological distress following bariatric surgery. This group is particularly hard to identify and may require the help of an expertly trained psychologist or counselor to deal with their cognitive or behavior issues.


Successful weight loss after bariatric surgery is often defined as greater than 50% excess weight loss (EWL). Many studies in the literature found that in the long term, more than 30% of patients fail to achieve this goal. Unsuccessful weight loss is also associated with a lack of resolution of comorbidities and reduced quality of life.


As with all my patients, I stressed that weight loss alone (in terms of kilograms) is not the only important outcome. The health benefits derived from successful weight loss should be the priority. Please refer to the section on “Defining successful weight loss”.

However for the purpose of discussing about weight loss, the next section will focus only on effective weight loss result and developing good eating habits.





Weight loss outcome


Needless to say weight loss result will vary widely amongst individuals. Many (genetic, environmental and individual) factors comes into play in order to achieve the desired successful weight loss and sometimes it is difficult to predict how successful or how much body weight a specific individual will lose.


As a rough guide, some of the known predictors of successful weight loss include:

  • Patients with a lower baseline (starting) body weight or BMI are more likely to achieve >50% EWL in the long term.
  • Those with more baseline lean muscle mass and less central/visceral fat lose more weight.
  • Gastric bypass patients lose more weight than those who had a sleeve gastrectomy (although the differences between the two is small) but certainly both procedures do significantly better than the adjustable gastric band.
  • The compliance and motivation of the individual patient is a significant factor.
  • To a lesser extent increase age, female gender, reduced height, diabetes and certain prescribed medications, cigarette smoking and the unemployed have inferior weight loss results.

Other factors may also predict a lesser weight loss result although they may be more difficult to prove. These include anxiety, depression and lack of social or family support.

It is important to stress the point that bariatric surgery will not achieve the optimal result unless this is accompanied by a permanent lifestyle and behavioural change, in terms of good eating habits and maintaining adequate physical activity after surgery. Please also refer to the section on “Lifestyle change – exercise”.




Eating disorder, nutritional deficiencies, psychological wellbeing and bariatric surgery


We need to deviate from our discussion on the usual post-operative lifestyle change to briefly mention the more serious problems of eating disorders and complications after bariatric surgery. We will highlight the differences between eating disorder (psychological problem) and maladaptive eating behavior (physiological problem). It is also difficult to distinguish eating disorders from the side effects of prescription medications.

The detection and early intervention for post-surgical disordered eating is important role to achieve optimal surgical outcomes. The role of the dietician is clearly indicated for this group of people. Although they charge a fee, such information may be invaluable in the long run.

Please refer to the section on “The cost for a dietician” or make an appointment to see a local accredited practicing dietician (specializing in weight loss and peri-operative bariatric surgery management).


It is worth spending time in this segment to identify some potential harmful or undesirable diet and eating habits. Patients and their general practitioners may not be aware that such problems already existed, which then resurface after bariatric surgery.

Individuals with pre-operative eating disorder are more likely to retain the same eating behaviour after surgery. Post-surgical eating disorder (binge eating and uncontrolled eating) is consistently related to poor outcomes such as poorer weight loss, more physical complications (nausea, vomiting, dumping) and gastric pouch dilatation resulting in early weight regain and greater psychological distress.

Those with a psychological condition, drug and alcohol dependence may struggle with compliance to proper eating behaviour after bariatric surgery.


Two types of binge eating behaviours have been identified:

  • Objective binge eating post-bariatric surgery is consumption of a large amount of food associated with a sense of lack of control.
  • Subjective binge episodes is a sense of lack of control regardless of amount of food consumed.

Some studies have reported that loss of control over eating (not the size or frequency of binges) is more predictive of the level of impairment and psychological distress in the post-operative period.

Post-surgical maladaptive eating is the result of poor behavioural adjustment to the altered gastrointestinal system, such as failing to adhere to recommendations of reduced portion sizes, chewing food thoroughly, eating slowly and limiting foods with high fat or sugar content.

  • The physical presentations of maladaptive eating may include reflux, food regurgitation, vomiting, diarrhoea, abdominal pain and feeling faint or nauseous (dumping syndrome).

It might be difficult to differentiate maladaptive eating from disordered eating. Maladaptive eating behaviour is restricting food choices to avoid vomiting (ie. obstruction/dysphagia from a very tight gastric band, gastric sleeve stricture or gastric bypass anastomotic stricture) or diarrhoea (ie. dumping syndrome). Patients may engage in bad compensatory behaviours to alleviate these physical symptoms, such as avoiding good quality solid meals and protein diet, replacing it with high calorie semisolid puree or liquids instead, consequently leading to weight regain and the return of adverse health problems.

In the maladaptive eating group food choices are often restricted or suffer from vomiting and diarrhea. They tend to graze throughout the day, chew and spit out food that is difficult to swallow in order to avoid or relieve the physiological symptoms of maladaptation.

  • An experienced bariatric surgeon is needed to investigate and to correct these anatomical rather than ignore the symptoms, labeling it as eating disorder or inappropriately referring the patient onto a psychologist. The classic example is patients with gastric band intolerance and maladaptive eating behavior, who is not properly counseled about the harmful side effects of malnutrition, reflux or aspiration complications and the need to have the band removed.

In the eating disorder group there may be hidden stress and psychological trauma from the past, which is difficult to detect.

  • The patients will need expert psychology help and counseling. A referral may be initiated by the surgeon, general practitioner or recommended by a dietician or even a family member.




Nutrition problems after a sleeve gastrectomy or Roux Y gastric bypass


Roux-en-Y gastric bypass (RYGBP) is one of the most effective bariatric procedurebut it may have nutritional deficiencies and long term metabolic consequences. Monitoring of vitamin and trace minerals with periodic blood tests is essential and supplementation may be needed long term.

The laparoscopic sleeve gastrectomy (LSG) has more commonly performed in Australia compare to the RYGBP because of its many advantages. The main one is that it causes less vitamin or mineral deficiencies and nutritional consequences (including dumping).

Nutrient deficiencies after a LSG may be due to decrease food intake (either in quantity or quality), lack of gastric acid secretion and/or accelerated gastric emptying or perhaps the neuro-hormonal alterations after surgery. LSG may decrease the production of intrinsic factor and hydrochloric acid (made worse by the prescription of proton pump inhibitors), which in turn may adversely affect vitamin B12 and iron absorption.

There have been several studies on the micronutrient effects after LSG but the results have been inconclusive at this point.Some report no deficiencieswhereas others report deficiencies in iron, vitamins D, B12, and B9.

Bear in mind these deficiencies may already have existed before surgery. However the important point here is to ensure patient have good quality meals after bariatric surgery and periodic blood test (especially for iron, folate, calcium, vitamin B12 and D) is recommended. These deficiencies are more common after RYGBP than LSG. With profuse vomiting it is important that the patients be given intravenous fluid hydration and vitamin B1 (thiamine) replacement as well. With severe malaborption, protein deficiency and vitamin deficiencies (A, D, E, K) needs to be screened and replaced.

In the long term patients who had LSG may not need as much supplements as those who had an omega loop minigastric or RYGBP. Hence it is easy to understand why some surgeons and patients prefer the LSG despite the bypass having a slightly superior percentage excess weight loss results and better reduction in the total and LDL cholesterol.


Pre-operative vitamin deficiencies

It is important to re-iterate again that obese patients are at risk of vitamin and nutrient deficiencies even before the surgery. These patients need to be tested and treated before surgery. Fortunately these blood tests are easy to perform by the general practitioners and are part of a standard health assessment when patients present to their local health facilities. For example even healthy young female patients have their blood tested to check for serum iron, folate, vitamin B12, thyroid function test, random blood sugar and cholesterol/triglyceride levels when they are pregnant.



Bariatric surgery especially LSG and gastric bypass are regarded as irreversible but it is also the optimal weight loss solution for patients with morbid obesity (BMI>40) or obesity (BMI>35) with associated medical problems for our Caucasian population.

However surgery alone is inadequate, to get the optimal results it needs to be accompanied by a permanent lifestyle change or behavior modification.

This section highlights the importance of a proper diet and nutrition after bariatric surgery to maintain weight loss, optimize physical health and quality of life.

  • Food portion control
  • Good food choices
  • Good eating habits

Patients, general practitioners and surgeons should educated and be aware of the common diet and nutrition problems associated with obesity and bariatric surgery and be able to recommend extra help when necessary.