Standardized inpatient protein-sparing modified fast as a bridge to metabolic/bariatric surgery in high-risk acutely ill adults with severe obesity.

BACKGROUND: Patients with severe obesity and acute medical decompensation face increased perioperative risk including respiratory compromise and thromboembolic events that complicate perioperative management. Data on structured inpatient preoperative dietary interventions in this population are limited. OBJECTIVE: To describe the feasibility and weight outcomes of a standardized inpatient protein-sparing modified fast (PSMF) protocol as a bridge to metabolic/bariatric surgery (MBS) in acutely ill adults with severe obesity. SETTING: University-affiliated academic medical center, United States. METHODS: We conducted a retrospective observational case series at a single urban academic center in Boston, Massachusetts, between July 2024 and May 2025. Weight loss during PSMF, percent total body weight loss (%TBWL), percent excess weight loss (%EWL), surgical outcomes, and short-term follow-up were assessed. RESULTS: Four of 5 patients initiated PSMF during hospitalization for life-threatening complications of severe obesity (baseline body mass index 46-122 kg/m2; weight 176.9-364.2 kg), including respiratory failure and significant cardiometabolic comorbidities. Over a 6-week period, %TBWL ranged from 8.97% to 15.38%, corresponding to %EWL of 13.27% to 23.68%. Three patients subsequently underwent robotic sleeve gastrectomy following PSMF. At 4-12 months follow up, %TBWL from admission ranged from 16.92 to 40.22%. One patient was unable to start PSMF due to avoidant/restrictive food intake disorder (ARFID). CONCLUSIONS: Inpatient PSMF was feasible and produced substantial short-term weight reduction that facilitated MBS in selected acutely ill adults with severe obesity. Careful screening for behavioral contraindications and multidisciplinary inpatient management were essential to success. Larger prospective studies are needed to further evaluate safety, optimal duration, and long-term outcomes.