Defining successful results after bariatric surgery


This blog provides free general information for anyone who is seeking to understand more about achieving optimal results after bariatric surgery, not intended as a medical consult. Please seek appropriate medical advice for individual assessment and management.


The crucial points are:

  • Understand what is regarded as the standard definition for successful excess weight loss.
  • Provide a rough guide as to how much weight loss is expected after bariatric surgery and identify some of the predictors of weight loss failures and weight re-gain in the longer term.
  • Most importantly realizing that the success of bariatric surgery can not be defined in terms of absolute weight loss alone, without describing the health improvements associated with weight loss.



The learning objectives are:

Being able to define what is the successful outcome of bariatric surgery in terms of:

  • Kilogram loss or BMI points loss
  • Health improvements (weaning of medications and reductions in complications normally associated with obesity)
  • Reduction in chronic inflammation, metabolic syndrome risk factors and premature cardio-vascular mortality
  • Physical improvements after surgery (better exercise tolerance, less fatigue, snoring and having good quality sleep)


The importance of adequate pre-op assessment and counseling:

  • In order to assess and understand the patient reasons for having weight loss surgery.
  • Explain what are the realistic expectations after bariatric surgery
  • Describe that weight loss results and improvements in body shape vary between individuals.
  • Appreciate that all patients will expect weight regain with time, even after a very successful initial operative outcome.
  • Understand need for a permanent lifestyle change and behavioural modification.
  • Ask for help (dietician, exercise physiologist, social support) when necessary.


List some of the predictors of weight loss:

  • Accept that results will vary widely for individual patient, because of biology, physiology and complex interactions with their physical illness and medication use.
  • Accept that with time weight re-gain is expected and is normal due to many reasons.




Surgeon’s advice to the patients during the pre-operative consultation

The most important starting point is to define the reasons for having bariatric surgery, what are the improvements in health as well as the physical, social and psychological benefits that can be potentially derived from surgery.

To stress the point again, weight loss alone (in terms of kilograms or reduction in body size) is not the most important reason and should not be the sole reason to pursue bariatric surgery. The emphasis should always be on the health benefits of bariatric/metabolic surgery before discussing the expected reduction in body weight.

Secondly the results of bariatric surgery will vary greatly amongst individuals due to many factors, despite having the same surgeon or the identical procedure. This blog will detail some of the predictors of successful weight loss.




Beyond weight loss


It is a major misconception amongst the public (even some doctors) that the only important outcome is total body weight loss (TBWL) or the percentage excess weight loss (% EWL).

Bariatric surgery is now recognized to have multiple additional benefits beyond weight loss that is considered more important:

  • In particular resolution (or stabilization) of medical conditions, especially Type 2 diabetes mellitus, cardiovascular and respiratory disease as well as the reduction in cancer incidence.
  • Weight loss significantly reduces the chronic inflammation and metabolic insults to the body, which helps to reduce the cardio-vascular risk factors and premature mortality.
  • Bariatric surgery results in improved functional status (fitness level, exercise tolerance) and psychological health (self image, confidence).
  • Bariatric surgery can significantly reduce hospitalizations and health-care costs related to treating obesity related co-morbidities.



The low uptake of bariatric surgery

On the other hand, to give the readers a contrasting view (and a wider perspective), there is a low uptake of bariatric surgery in our community.

Despite the ample evidence on the health benefits of surgery on the obese patients with associated medical problems, the penetrance of surgery into clinical practice is still in an infancy stage.

This may be due to various factors such as:

  • Patient lack of knowledge on the benefits of bariatric surgery.
  • Patient does not wish to undergo a major lifestyle change after surgery, such as restriction in food intake, change over to healthy meals and following a regular exercise program.
  • The misconception or fear infused by other members of the community that obesity is a failure of dieting and that surgery (sleeve gastrectomy and gastric bypass) is an irreversible procedure.
  • Lack of funding to have surgery (in Australia the majority of the operations are only done in private hospitals).
  • General practitioners and specialist physicians not referring suitable patients for surgery.



Although the above are all valid reasons for the low uptake of bariatric surgery in our country, my personal feeling for this failure is that too many people (maybe including some doctors) still think of bariatric surgery as a procedure for weight loss and not for improvements in health.

Please refer to the section on “Understanding visceral obesity and metabolic syndrome”.





Excess weight loss and evidence from the surgical literature

The second aspect of this blog concentrates on weight loss, which often is the main topic of discussion that patients would like to talk about. Hence the bulk of this section is dedicated to explaining what are normal expected weight loss and the predictors of successful bariatric surgery outcome.

Industry standard describes bariatric surgery as successful when patients achieved over 50% excess weight loss (EWL) maintained over the long term.

Historical studies report their results in absolute weight loss, although this can’t be applied to all patients, it is still helpful to know what is the range of weight loss that is reasonable or realistic.

  • One big meta-analysis from North America, by Dr. Buchwald, reported mean weight loss result to be between 36.6 to 40.5kg at 2 to 3 years after surgery. This is the collective result of all bariatric procedures (which includes gastric bands, gastroplasty, Roux Y gastric bypass (RYGBP) and bilio-pancreatic diversions/duodenal switch) and some of these procedures are rarely performed in Australia. However if we isolate the RYGBP as gold standard in North America, the expected absolute weight loss is reported to be up to 47kg.


There have been several studies recently comparing laparoscopic sleeve gastrectomy (LSG) with RYGBP. These studies concluded that results are better with the bypass but the differences in weight loss and improvements in medical co-morbidities are not statistically significant between the two operations. Hence given the many advantages of a LSG and the long-term undesirable metabolic complications of RYGBP, many surgeons advocate the LSG to be the primary weight loss procedure.

A recent review from Bariatric Outcomes Longitudinal Database (BOLD) from North America (published in February 2014), reported that the 1year result after LSG and RYGBP is comparable with little differences between the two.

  • For those with starting body weight of 100kg, the LSG group lost 30kg and RYGBP group lost 34kg.
  • For those with starting weight at 150kg, the LSG group lost 46kg and RYGBP group lost 52kg.
  • In contrast the gastric band group performed poorly, with less than half the weight loss achieved from the other two procedures.





Predictors of weight loss

Objectively results can only be gauged in terms of absolute weight loss, BMI loss, resolution or reduction of comorbid conditions associated with morbid obesity.

And despite achieving significant weight loss results and reductions in medical risk factors after bariatric surgery with no complications, there will be some patients who will not be satisfied with the result.

It may be a difficult task to explain to them that further weight loss beyond 1 year will not be possible. Hence the next section will discuss the predictors of successful weight loss and the barriers to exercise.


It is difficult to explain the predictors for successful weight loss or to explain the large variations in total weight loss results after bariatric surgery.

Amongst the predictors of successful weight loss listed in some studies 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 either procedure is significantly better than adjustable gastric band.
  • The compliance and motivation of individual patient is also a significant factor.
  • To a lesser extent increase age, female gender, reduced height, diabetes and certain prescribed medications, cigarette smoking or the unemployed also contribute to inferior results.



Medications that may have weight gain side effects include:

  • Steroids (prednisolone) for asthma or inflammatory disorders
  • Anti-depressants and anti-psychotic medications
  • Medications for diabetes mellitus and hypertension
  • Medications for acid suppression or heartburn
  • Antihistamine medications


Antidepressants are suspected to cause weight gain. Tricyclic antidepressants (amitriptyline), monoamine oxidase inhibitors (phenelzine, tranylcypromine) are more likely than common SSRI anti-depressants (Prozac, Xoloft, Lexapro, Paxil) to have weight gain side effects. Common antipsychotic medications include drugs to treat schizophrenia, bipolar affective disorders, epilepsy and migraine have their therapeutic effects by altering the neurotransmitters in the brain, but in doing so it may also affect hunger and satiety control. Medications such as clozapine, olanzapine and lithium are in this category.

Diabetes medications either tablets (glipizide, sulfonylureas) or insulin has the ability to lower blood sugar and consequently stimulate appetite as well. However metformin is believed to be weight neutral.

Antihypertensives such as calcium antagonist may cause fluid retention and beta blocker may result in fatigue or slower metabolic activity. Steroid use may result in fluid retention and fat deposition in the trunk (neck, waist).



* Never stop or substitute your medications, they are prescribed for a very important reason. Please consult your GP or specialist before altering your medications.






Facts on weight loss surgery

There are two well-known facts in bariatric surgery:

  • Firstly patients who are morbidly obese (BMI>40) require a more aggressive procedure, such as the sleeve gastrectomy or gastric bypass. The heavier the starting body weight or BMI, the more difficult is the task of losing weight (>50% EWL or % BMI loss) and sustaining that loss is also more difficult. This may partially explain why many of the super obese (BMI>50) and above do not achieve a satisfactory percentage excess weight loss even after a gastric bypass.
  • Secondly post-operative weight loss mainly occurs in the first 6-12 months and further excess weight loss is rarely possible after 1-2 years. This is the period of time where weight re-gain begins.


What we know less of is the predictors of successful weight loss or the selection criteria of ideal candidates for bariatric surgery, picking those who will achieve impeccable result. Fortunately some studies have emerged to shed some light into this area recently.

Pre-operative health status is a powerful predictor of continued weight loss. Those without medical co-morbidities (on multiple medications) or physical illness (such as arthritis) have better weight loss results. Good psychological health and happiness, strong personal support and satisfaction in life, good eating habits (no eating disorder) are all significant contributors to a successful maintained weight loss result. Patients with good coping skills, optimistic and expecting major and widespread improvements in their personal lives as a result of the surgery also tend to do better.

This highlights the importance of realizing that surgery is a starting point (initiating step) and not the only reason resulting in long-term weight loss maintenance. A significant lifestyle change and permanent behavioral modification is really the key.

In other words bariatric surgery aside, sustaining long-term weight loss really requires personal motivation, structured plans, both a mental and physical effort (lifelong step).

This is difficult to achieve without the support or assistance of an understanding general practitioner or physician (with special interest in bariatric medicine), dietician, psychologist and an exercise physiologist.



Conversely patients who are less likely to achieve good results despite a perfect operation, include those with a high anxiety and distress levels, low self-esteem, poor eating habits, drug and alcohol dependence, poor coping skills, lacking personal supports and those low level of personal motivation or compliance.

As a general rule bariatric surgery works better for those who eat large portion meals and snacks frequently (hunger control problem), less successful for those with emotional eating behavior (psychological or eating disorder problem).






Weight re-gain after bariatric surgery



It is important that patients understand that with the passage of time, almost everyone will regain some weight, regardless of the procedure, even after a Roux Y gastric bypass (RYGBP). In fact some studies report that over 30% did not achieve over 50% EWL after RYGBP.


The reasons are often multi-factorial, because of genetics, biology, physiology, environment and complex interactions with their physical illness and medication use, as already alluded to above.

There is a reduction lean muscle mass and basal metabolic rate from increasing age as well as hormonal changes (especially approaching menopause), where weight gain is natural. Unfortunately no surgery can revert patients back to their teenage years, with a lower BMI and more youthful body shape or appearance.



Post op lifestyle change: diet and exercise

Post op weight re-gain is attributed to a combination of genetic, biological, environmental, behavioral and psychological influences. We will never be able to account for all these factors, some of them are inherent and beyond the control of us humans.

But it is worth mentioning some the avoidable technical or patient factors in an attempt to encourage patient to change their lifestyle after surgery to prevent weight re-gain.

Needless to say having the surgery performed correctly and without complications is essential. Despite that even the best surgeon or the best centres have a failure rate and revision surgery may be required.

Technical factors with the sleeve gastrectomy:

  • The remnant stomach (especially the fundus and antrum) may dilate with time, resulting in loss of restriction, increased food portion size and partial weight re-gain.
  • Some of the revisional procedures that are available to amend this include a re-sleeve gastrectomy, gastric plication, convert to a gastric bypass (RYGBP or the omega loop minigastric bypass) or convert to a version of the duodenal switch procedure.

Technical factors with the gastric bypass:

  • The residual gastric pouch may stretch or the diameter of the gastrojejunostomy may enlarge, again resulting in loss of restriction.
  • Various revisional procedures have been suggested, including trimming/reconstructing the gastric pouch or gastrojejunal anastomosis or both. Endoscopic suturing (including StomaphyX or Ovesco OTSC clips) to reduce gastric bypass pouch and stoma diameter or placement of adjustable gastric band have been reported but experiences with such endoscopic procedures are limited and the long term durable results are yet to be proven.
  • Traditionally the convention is placement of a silicone band on the proximal gastric pouch or revising the standard Roux Y bypass to a variant of a long limb gastric bypass but this potentially has severe malabsorption side effects and metabolic consequences.



Finally back to the discussion that was raised above, it is important for patients and surgeons to understand and appreciate that bariatric surgery alone is not the answer. But this should be complemented by active patient participation in the weight loss project by adhering to advice regarding post op diet, nutrition and keeping up with a regular physical or fitness training program.

Please refer to the section on “Lifetsyle change – diet” and “Lifestyle change – exercise”.