Background: This systematic review assessed feasibility and effectiveness of preoperative meal replacements to improve surgical outcomes for obese patients.

Methods: PRISMA guidelines were followed and electronic databases searched for articles between January 1990 and March 2015.

Results: Fifteen studies (942 participants including 351 controls) were included, 13 studies (n = 750) in bariatric patients. Adverse effects and dropout rates were minimal. Ten out of 14 studies achieved 5–10 % total weight loss. Six of six studies reporting liver volume achieved 10 % reduction. Endpoints for perioperative risks and outcomes were too varied to support definitive risk benefit.

Conclusions: Commercial meal replacements are feasible, have minimal side effects and facilitate weight loss and liver shrinkage in free-living obese patients awaiting elective surgery. A reduction in surgical risk is unclear.