Predictive value of 6-minute walk test for weight loss after bariatric and metabolic surgery in individuals with class III obesity

BACKGROUND: Class III obesity is associated with wide variability in early weight-loss response after metabolic and bariatric surgery (MBS), creating a need for simple preoperative measures that can help stratify risk for early nonresponse.

OBJECTIVE: To determine whether preoperative physical functional capacity, assessed by the six-minute walk test (6MWT), predicts short-term weight loss outcomes following MBS.

METHODS: In this retrospective study, a total of 164 adults (mean age = 43.1 ± 10.9 years) with class III obesity underwent MBS, predominantly laparoscopic Roux-en-Y gastric bypass or sleeve gastrectomy. Three 6MWT models using (1) absolute distance, (2) percentage of predicted distance, and (3) 6MWT/body mass index (BMI) were evaluated to predict nonresponse, defined as less than 45% excess BMI loss at six months. Patients were split into development and validation cohorts. Predictive performance was assessed with receiver operating characteristic curves, area under the curve (AUC), sensitivity, and specificity.

RESULTS: Patients achieved a total body weight loss of 26.0 ± 6.9% and excess BMI loss of 57.3 ± 18.0% (76.6% follow-up). Model 3 showed the strongest predictive performance (development AUC = 0.74; validation AUC = 0.78). Model 1 demonstrated high sensitivity (0.83) but lower discrimination (validation AUC = 0.67).

CONCLUSIONS: Preoperative 6MWT performance provides promising prognostic information for early nonresponse to weight loss following MBS. The 6MWT/BMI ratio showed the strongest and most consistent predictive performance within our cohort, supporting its potential role as a valuable supplementary risk stratification tool. Absolute 6MWT distance may serve as a high-sensitivity screening tool. When used in conjunction with other clinical assessments, this two-step approach may help identify patients at risk for nonresponse and guide targeted perioperative interventions.