Obesity is a worldwide pandemic affecting about 1/3 of the adult population. Objectively, it is defined as a body mass index (BMI) equal to or higher than 30 kg/m2. The World Health Organization defines obesity as a condition of excessive fat accumulation in the body to the extent that health and well-being are adversely affected.
It is associated with important comorbidities such as type-2 diabetes mellitus, hypertension and dyslipidemia, and it is related to higher cardiovascular risk, and, consequently, increased morbidity and mortality.
Bariatric Surgery is the most effective treatment for obesity, providing long-lasting weight loss and resolution of comorbidities. The effects of bariatric surgery vary depending on the patient, the chosen procedure, the initial BMI and the initial comorbidity status.
A variety of bariatric procedures are currently performed, which are subdivided depending on the main mechanism of action into restrictive or malabsorptive. Restrictive procedures act mainly by reducing the amount of food intake, without changes in the normal pathway of the gastrointestinal tract. Malabsorptive procedures are characterized by reducing the length of intestine in contact with food. Most malabsorptive procedures have a restrictive component and are truly combined.
The most commonly performed procedures are Sleeve Gastrectomy and Roux-en-Y Gastric Bypass, representing 90% of all the procedures performed.
Reports in literature reveal a percentage of excess body weight loss (EWL%) of near 80% (with some procedures), a long-time remission of type-2 diabetes in 23 to 60% of patients and a remission of hypertension near 50%.
The majority of reports refer to the effects of surgery in weight loss, with definitions of weight loss “success”, weight loss “failure” and weight “regain” being currently and frequently used.
Definitions of Response after Bariatric Surgery
In December 2018, Bonouvrie DS et al published a Systematic Review in Obesity Surgery that highlighted the importance of standard definitions for bariatric surgery results, proposing terms that would be more accurate.
The authors proposed defining the outcomes of bariatric surgery as a response and patients as responders: primary responders (patients who achieved the expected weight loss), primary non-responders (patients who did not achieve the expected weight loss) and secondary non-responders (patients who, at a certain point in follow-up, achieved an adequate loss, but then regained weight).
The authors analysed all articles published between July 1st 2014 and July 1st 2017, regarding adult patients, referring to at least one of the 3 common outcomes described, and all the correspondent definitions of the 3 outcomes proposed. One-hundred and twelve articles were included, containing a total of 191 outcome parameters. Fifty-four percent of the articles gave a definition of the outcome, but about 1/3 of them did not give a definition or a description. A total of 13 definitions for primary responders was encountered, 23 definitions for primary non-responders and 18 definitions for secondary definitions.
This systematic review showed how inconsistent and variable the reports of outcomes in bariatric surgery are and how they are not comparable, since there is no standard definition of outcomes.
This lack of uniformity allows authors to manipulate the results, adjusting definitions towards their goal.
As with many other medical and surgical conditions, an international consensus to define the results of bariatric surgery is required. Not only because obesity is a pandemic disease and a growing number of patients is being submitted to surgery, but because uniformity is paramount to compare and evaluate results. It is mandatory to distinguish between primary and secondary non-responders and to properly understand who will benefit from revisional surgery and who will not achieve the right goals with a new surgery that may expose the patient to higher morbidity.