According to several national and international guidelines, the management of weight excess requires a multidisciplinary approach (medical doctor, dietitian, nurse, psychologist, surgeon, anaesthetist, and pharmacist) with different levels of intensity based on patient’s characteristics and different clinical situation[20–24]. A first level of intervention involves a nutritional counselling approach and an increase in physical activity. A second level provide a Hospital Diagnostic and Treatment Protocol involving a multidisciplinary team with experience in the field of obesity treatment. Third level of intervention should include patients eligible for BS[23].
BS is known to be most effective in weight reduction in patients with severe obesity compared to other medical treatment[9, 25–27] and in the improvement of comorbidities related to obesity, such as type 2 diabetes[25, 28–30], hypertension[31] and dyslipidaemia[9, 32]. It also improve mortality [33, 34] and QoL. Despite these advantages, this procedure may present some critical issues, such as complications (perioperative, surgical, gastrointestinal, nutritional and psychological)[35] and partial weight regain [36].
Our Bariatric Surgery Protocol provides a first assessment by Bariatric Team to evaluate patient’s eligibility to BS and to define the most appropriate technique of surgery (VBG, GB or LSG). This protocol provides two years of follow-up after BS, as recommended by guidelines[20, 37]. After first two years post-BS timing of nutritional follow-up is individualized, with many patients who are not followed-up in the medium- and long-term.
Our retrospective cohort study investigated, from different complementary point of view, in a large sample of patients and over a medium-term follow-up time, weight loss and excess weight loss average trend after BS, median time to reach clinical goal and median time of clinical goal maintaining, by different bariatric surgical techniques (VBG, GB and LSG).
The size of the samples of patients and visits collected over a quite long period represents a major advantage of our work and had allowed the use of advanced statistical methods.
In agreement with current knowledge, our data highlight a common trend of average trajectories of %TWL and %EWL in the three cohort of patients, consisting in a rapid increase of TWL and EWL in first two years after surgery, followed by a slight but constant decrease which starts at about two years after surgery[10, 18, 38, 39]. Our estimates of yearly average total weight regain ranged from 1.0% for GB to 2.9% for VBG and were comparable to those reported in literature[36].
Estimated share of patients that reach clinical goal quickly rises in the first two years after all types of bariatric surgery, whereas after this time only a few patients reach clinical goal. This trend is common in each cohort of patients.
At 2 years after BS cumulative incidence of clinical goal reached was very high in the three cohorts (70.7% in VBG, 86.4% in GB and 83.4% in LSG). Only for GB there is an additional 3% of patients who reach the clinical goal from 2 to 4 years.
Median time-to goal was 13.2 months in VBG cohort, 9.6 months in GB cohort and 10.2 months in LSG cohort. Median time of clinical goal maintaining was 4.8 years for VBG, 6.6 years for GB and 5.3 years for LSG.
These data suggest that patients who do not reach the clinical goal within two years, hardly will reach it later. Moreover, after two years from reaching clinical goal, share of patients unable to maintain it progressively increases, regardless of type of surgical treatment employed.
Changes in body weight that we observed may depend on several reasons.
Firstly, the structure of our protocol provides only two years of systematic follow-up after BS. It is well known that patients undergoing regular evaluations by a Nutritional Team, with or without bariatric surgery, can maintain clinical goal longer[40, 41]. Without a systematic long-term follow-up programme, patients can lose compliance to nutritional indications as well as to daily physical activity easier then patients regularly followed by Nutritional Team[38, 40, 42–44].
Changes in hormonal and metabolic mechanisms after BS, matched to psychological factors, can also lead to an increased food intake, causing weight regain after an initial weight loss[36, 45, 46]. Weight loss after BS are due to anatomical exclusion of gut and/or the restriction of volume capacity of stomach[47–51]. With time, the initial alteration of hormonal level decrease and increased levels of ghrelin, decreased YY peptide and GLP-1 levels, episodes of hypoglycaemia after bariatric surgery are reported in literature[52–56]. Moreover the appearance of anatomic surgical failure, including gastric sac enlargement and gastric fistulas could be responsible of weight regain; this complications are associated with reduced satiety and increased food intake[36, 51].
These data confirm the effectiveness of BS in patients with obesity but highlight the need for a systematic medium- and long-term follow up, to prevent weight regain.
Results of this study may be useful to both clinicians and patients, as they provide easily readable information about the most relevant clinical aims that are pursued in patients with obesity undergoing BS. For example, our data can be used to provide informed counselling about expected long-term weight changes for patients scheduled for BS. A longer follow-up period after BS could lead to change in the structure of BS protocols. A higher follow-up rate by Nutritional Team should be planned to motivate patients to a strict compliance to both dietary recommendations and physical activity.
Our study also has several limitations. Firstly, the retrospective design did not allow the collection of systematic medium- and long-term follow-up data. Secondly, the three cohorts of patient VBG, GB and LSG are not comparable as they present different clinical characteristics which reflects the different surgical approaches. For this reason, the three average trajectories of %TWL and %EWL could not be compared between interventions. Thirdly, no information is available about co-morbidities before BS and their progression after BS.