The recent IFSO consensus provided standard terminology and definitions for bariatric and metabolic surgery across the world to be used for the future

Obesity is now regarded as a chronic, relapsing, multifactorial, multi stage, neuro behavioural disease

Hence multiple treatments or interventions may be needed in the long term including re-operations for suboptimal treatment response, recurrent weight gain or to treat procedure related complications

Revisional or conversion bariatric surgery is complex and technically challenging and the patient’s response is difficult to predict

The role of the dietitian and psychologist as well as managing patient expectations have become more important

• The emphasis is on lifestyle change rather than focusing solely on the amount or percentage of body weight loss is important
• There is a qualitative as well as quantitative measure for a successful outcome after bariatric and metabolic surgery

New definitions   % Total weight loss (% TWL) This is the percentage of total weight loss compared to the pre-operative weight *TWL is least affected by the baseline weight and remains relatively constant for a given procedure across different classes of obesity   Revisional procedure Revision or modification for a procedure that does not encompass a new procedure with a new mechanism of action or reversal of the surgical anatomy *This procedure is correction or enhancement of the same procedure, such as revision of the gastric pouch or distalization of the gastric bypass   Conversion procedure This is changing from one procedure to another with a different mechanism of action   Reversal procedure This is reversing a procedure back to the normal anatomy   Adequate weight loss Is more than 20% TWL and/or improvement of obesity related complications This term has replaced “success”   Suboptimal clinical response (SoCR) Is less than 20% TWL or no improvement or worsening of any obesity related complications that were part of the indication for surgery The prevalence of SoCR is about 3 to 16% This term replaced “insufficient weight loss” or “weight loss failure”   Recurrent weight gain (RWG) Is late weight regain after optimal clinical response initially *RWG occurs and is normal after all bariatric operations *The prevalence of RWG ranges from 43.6 to 86.5% 5 years after nadir   Late clinical deterioration Is a secondary deterioration after an initial period of optimal clinical response Is RWG >30% of the initial TWL or recurrence/worsening of obesity related complications that were significant before surgery

Changing trends   The National Institute of Health (NIH) 1991 criteria or guidelines for bariatric for the last 30 years had changed   In 2022 IFSO and ASMBS have jointly produced updated guidelines for metabolic and bariatric surgery   In 1994 laparoscopic RYGBP was first performed in the USA Laparoscopic surgery allowed earlier discharge from hospital, low (<5%) 30 day re-admission rate, low (3.2%) complication rate within the first 30 days   Nowadays in 2025 laparoscopic and robotic gastric bypass procedures have low complication rates, surgical site infection, pulmonary complications and mortality with significant advantages over the open surgery   Between 2006 to 2012 the English reported inpatient mortality rate was <0.15% for all procedure types Between 2007 to 2012 the French reported 0.12% 90 day mortality rate Between 2008 to 2017, the Scandinavian reported 0.06% 30 day mortality rate and 0.19% 1 year mortality rate Between 1990 to 2003 the Buchwald (USA) meta analysis reported 0.1 to 1.1% 30 day mortality rate

Unchanging trends   Although the indications for surgery have changed and there are improved safety records, the long term weight loss result are not always maintained, with the risk for suboptimal weight loss or weight regain with time after any types of bariatric procedures   Successful weight loss after surgery is defined by the amount and durability of weight loss and control of obesity related complications   Maximum weight loss is usually reported at 1 to 2 years, the nadir   Weight regain potentially occurs with all types of bariatric procedures Weight often stabilise after 8 to 10 years *Lifestyle interventions has not been shown to reduce recurrent weight gain *Weight regain is often multi factorial, which include poor dietary adherence (high carbohydrate and alcohol intake), behavioural, psychological (binge eating or grazing), lack of support and physical inactivity *Other factors include central nervous system signalling, hormonal and genetic factors   Recurrent weight gain may include *Regain >10kg *Regain >5 BMI points *Regain >10% of pre surgery weight *Regain of >10-15% of nadir weight *Regain of >10-25% of maximum TWL at nadir   All 5 measures above are associated with the progression of diabetes, hypertension, decline in physical health related quality of life and decline in satisfaction with surgery   Clinical deterioration is defined as RWL >30% of maximum TWL or worsening of obesity related complication that was a significant indication for surgery

For the dietitian   Maladaptive eating behaviour include grazing on soft foods and sweets *Restrictive procedures such as the gastric band or sleeve may trigger food intolerances and maladaptive eating behaviour *Excess alcohol use is a common cause for weight regain   After metabolic and bariatric there is increased alcohol absorption and higher blood alcohol level as well as the potential for alcohol abuse after surgery

For the psychologist   Depression is common before the first index operation The depression symptoms may improve in the first 1 to 3 years after bariatric surgery But depression is often a recurrent condition, can recur in the long term and negatively impact weight outcomes   Anxiety and depression are common amongst patients needing revision bariatric surgery Psychological disorders are common, can be chronic, recurrent or under treated and include assessment for suicide risk   Opioid consumption may increase after bariatric surgery as well Patients need to be assessed for chronic pain and pain management strategies Patients need to be assessed for substance abuse     Metabolic and bariatric surgery with significant long term weight loss result may lead to psychological, interpersonal, body image, lifestyle and relationship changes that require adjustment and the patient responses to these changes are diverse   These lifestyle changes may be stressful and lead to maladaptive coping response or eating behaviour Eating disorders may recur after successful weight loss or occur de novo

Addressing patients’ expectations   Unrealistic weight loss expectations are common and may be more so in revision bariatric surgery *Improvement in physical health and resolution of obesity related medical co-morbidities are more important to health care professionals *Self esteem are more important to the patients   The amount of weight loss required to improve co-morbidities may be less than the amount of weight the patients wish to lose to improve their mental well being