Poster Presentation Australian and New Zealand Obesity Society Annual Scientific Conference 2026

Impact of pre-operative psychiatric comorbidity on weight loss outcomes after bariatric surgery at a single tertiary centre  (#119)

Rosie Charge 1 , Elisia Manson 2 , Jessica Swinbourne 2 , Hannah Nelthorpe 2 , Samantha Hocking 1 2 3 , Janet Franklin 1 2 4
  1. Faculty of Medicine and Health, University of Sydney , Sydney, NSW, Australia
  2. Metabolism & Obesity Services , RPAH SLHD, Sydney, NSW, Australia
  3. Charles Perkins Centre, University of Sydney , Sydney, NSW, Australia
  4. Eating Disorders and Nutrition Research Group, Translational Health Research Institute, Western Sydney University, Sydney, NSW, Australia

Background: Psychiatric comorbidity is common amongst bariatric surgery candidates and may influence postoperative weight loss outcomes. However, evidence remains inconsistent. Clarifying its impact on percentage total weight loss (%TWL) after bariatric surgery may improve perioperative risk stratification and support.

Aim: To determine whether pre-operative psychiatric comorbidity and/or baseline PROMIS-29 symptom severity are associated with %TWL up to three years following primary bariatric surgery.

Methods: This retrospective cohort study included patients undergoing primary bariatric surgery between January 2020 and May 2026 with annual weight data available for up to three years (n=93). Patients were classified as having psychiatric comorbidity (documented psychiatric diagnosis and/or psychotropic medication use, n=48) or no psychiatric comorbidity (n=45). Baseline PROMIS-29 data were available for a subset (n=28). %TWL was assessed at approximately12, 24 and 36 months. Linear mixed-effects models (LMM) with random intercepts and slopes evaluated associations between psychiatric comorbidity and longitudinal %TWL, adjusting for age, sex, baseline BMI and procedure-type.

Results: Psychiatric comorbidity was not associated with %TWL (β=1.99%; SE 2.74; p=0.469) and there was no psychiatric comorbidity × time interaction (β=0.07; p=0.968). Considerable inter-individual variability in weight-loss trajectories was observed (time-slope variance 25.81, SD 5.08). A moderate negative correlation between intercept and slope (r=-0.56) suggested greater initial weight loss was associated with subsequent plateauing. Single anastomosis gastric bypass was independently associated with greater %TWL than sleeve gastrectomy (β=5.77%; p<0 .005). PROMIS-29 analyses identified higher pain severity in patients with psychiatric comorbidity (87.5% higher mean severity; p<0.05), with no differences in other domains.

Conclusions: Pre-operative psychiatric comorbidity was not associated with postoperative %TWL. Higher pain severity despite similar weight loss outcomes suggests symptom burden and diagnosis capture distinct aspects of patient experience. Diagnosis-based classifications alone may not reflect clinically relevant heterogeneity and should not restrict access to bariatric surgery.