Optimizing postoperative outcomes after gastric bypass surgery-the influence of dietary protein and its amino acid composition: A systematic review

Background and Aims: Bariatric surgery has emerged as an effective method to reduce morbid obesity. Nutritional counseling is essential in order to achieve maximal treatment success and to avoid long term complications. Increased dietary protein intake or its amino acid composition could have beneficial influence on various postoperative results. The aim of this systematic review is to examine the level of evidence of the relationship between dietary protein intake or supplementation with amino acids and postoperative outcomes after gastric bypass surgery. Material and Methods: We conducted a systematic literature search in four electronic databases (Cochrane Central Register of Controlled Trials, EMBASE, Pub Med and Scopus). Results: Out of 6043 hits, nineteen studies were included, seven randomized and twelve non-randomized studies with varying study designs, interventions and outcomes. For most postoperative outcomes, studies did not provide solid evidence of any beneficial effect. Only an increased dietary protein intake was associated with improved weight loss after gastric bypass surgery, but the level of evidence is low (Grade C). Conclusion: The study of the influence of protein and its amino acid composition represents an important developing domain of knowledge and needs further attention considering the high popularity of bariatric surgery. For future study purposes, we recommend a clear description of the exact quantity and composition of the proteins and amino acids in the diet or supplement.