Systematic review and meta analysis of effect of pre operative low calorie diets in bariatric surgery

Saurav Chakravartty, MBBS, MRCS, MS, A G Patel, FRCS, MS

King’s College Hospital, London


Low and very low calorie diets are often used to encourage pre operative weight loss in patients selected for bariatric surgery to help improve technical ease of surgery. These diets can shrink the liver and decrease intra abdominal fat thus improving vision and manoeuvrability. The objective of this study was to perform a systematic review and meta analysis of the literature to ascertain whether these diets actually improve operative ease objectively.


A systematic review of medical literature between 1990 and 2012 was conducted using Medline, Embase, Cochrane, Ovid, CINAHL and Pubmed databases. The eligibility criteria included all papers that mentioned a low or very low calorie diet used for inducing weight prior to bariatric surgery and included information on perioperative events on patients undergoing bariatric surgery. Operative ease was estimated by comparing operating time, blood loss and complications between both groups. The meta analysis was performed with Cochrane Review manager version 5.1 where a random effects model for dichotomous data and inverse variance method for continuous data was used. Sensitivity analysis was also performed using funnel plots.


473 articles were identified of which 2 eligible studies were found which included one randomised controlled trial and one prospective non randomised trial. Overall 151 patients in the diet group were compared to 155 patients in the non diet group and all patients underwent a laparoscopic roux-en y gastric bypass. Both groups were comparable in age (39 vs 40 years) and body mass indices (43 vs 43 kg/m2).The mean decrease in weight following the diet ranged between 5 and 7.5 kg. On the meta-analysis there was no difference in operating time (mean difference:-1.10, 95% Confidence Intervals: -6.19-4,p=0.67) and post operative complications (odds ratio:1.01, 95% Confidence Intervals:0.11-9.34,p=0.99) between the groups. Heterogeneity of the data was moderately low (I2=0-69%).


Low calorie diets do not objectively improve the technical ease of a laparoscopic gastric bypass and therefore routine preoperative use of such diets in bariatric surgery may not be necessary.

Session: Poster Presentation

Program Number: P421

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