Bariatric surgery reduces branched-chain amino acids' levels: a systematic review and meta-analysis

Bariatric surgery is a metabolic surgery known to be an efficient treatment for weight loss, with adequate long-term maintenance. Interestingly, some studies have reported a reduction in branched chained amino acids (BCAAs) after bariatric surgery, which putatively contributes to post-surgical metabolic improvement. The current systematic review and meta-analysis investigated the effect of bariatric surgery on the level of BCAAs. PubMed, SCOPUS, EMBASE, and Web of Science databases were searched from their inception to July 2019. All clinical trials which investigated the effect of bariatric surgery on the levels of valine, leucine, and isoleucine, for more than one week, were included. Nine studies (11 effect sizes) were analyzed via meta-analytical techniques using random-effects models. The pooled data suggested that bariatric surgery significantly reduced the valine (standardized mean difference [SMD]: -1.89, 95% confidence interval [CI]: -2.79, -0.99, I² = 90.9%), leucine (SMD: -0.96, 95% CI: -1.48, -0.44, I² = 72.4%), and isoleucine (SMD: -0.58, 95% CI: -0.84, -0.31, I² = 66.3%) levels after surgery compared with before the surgery. Overall, bariatric surgery significantly reduced the levels of valine, leucine, and isoleucine compared with before the surgery. Further large-scale and homogenous trials are needed to better discern the generalizability of our findings.