Very low energy diets for obese patients before non-bariatric surgery

PReoperative Very Low Energy Diets for Obese PAtients Undergoing Non-bariatric Surgery: A Randomized Evaluation (PREPARE Pilot)

Not applicable Interventional McMaster University · NCT05918471

This study is testing whether a very low energy diet can help obese patients lose weight before non-bariatric surgery to reduce risks during the operation.

Quick facts

PhaseNot applicable
Study typeInterventional
Enrollment88 (estimated)
Ages18 Years and up
SexAll
SponsorMcMaster University Academic / other
Locations4 sites (Hamilton, Ontario and 3 other locations)
Trial IDNCT05918471 on ClinicalTrials.gov

What this trial studies

This pilot randomized controlled trial aims to evaluate the feasibility of using preoperative very low energy diets (VLEDs) compared to standard care for obese patients undergoing elective non-bariatric surgery. Participants with a BMI over 30 kg/m2 will be randomly assigned to either a 3-week VLED regimen with weight loss counseling or counseling alone. The study focuses on assessing recruitment, compliance, and follow-up to determine the viability of a larger trial that would measure differences in postoperative outcomes. The goal is to mitigate the risks associated with obesity during surgical procedures.

Who should consider this trial

Good fit: Ideal candidates are adults over 18 years old with a BMI greater than 30 kg/m2 who are scheduled for major elective non-bariatric surgery.

Not a fit: Patients undergoing bariatric surgery, urgent surgeries, or those with significant comorbidities such as severe renal or liver dysfunction may not benefit from this study.

Why it matters

Potential benefit: If successful, this approach could lead to improved postoperative outcomes and reduced complications for obese patients undergoing surgery.

How similar studies have performed: Previous studies have shown that preoperative VLEDs can lead to significant weight loss in obese patients undergoing various surgical procedures, indicating potential for success in this approach.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Older than 18 years of age
* BMI of greater than 30 kg/m2
* Undergoing major elective non-bariatric surgery. Major surgery is defined as any operation performed under general anesthesia requiring a skin incision extending beyond the subcutaneous tissue.

Exclusion Criteria:

* Undergoing bariatric surgery
* Undergoing neurologic surgery
* Undergoing urgent or emergent surgery
* Recently diagnosed myocardial infarction or unstable angina (i.e., within past six months)
* Diagnosed moderate-to-severe renal dysfunction (i.e., eGFR less than 30mL/min/1.73m2)
* Diagnosed severe liver dysfunction (i.e., cirrhosis, portal hypertension, hepatic encephalopathy, hepatorenal syndrome)
* Recently diagnosed alcohol or drug use disorders (i.e., excessive use of substance within past six months)
* Experienced a recent episode of gout (i.e., within past six months)
* Medical history of porphyria; (10) Known allergy to any Optifast ingredient
* Enrolled in other prospective studies with similar interventions and/or outcomes. Co-enrollment may be deemed appropriate if the steering committees of the respective trials review the details of participation.
* Pregnant or breastfeeding women
* Patients unable to provide informed consent.

Where this trial is running

Hamilton, Ontario and 3 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions ObesityNon-Bariatric SurgeryPreoperative Weight LossPreoperative Optimization
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.