RESUMEN
CONTEXT: Recent evidence suggests that modulation of the gut microbiota may contribute to body weight control. OBJECTIVE: This systematic review aimed to assess the effects of oral supplementation with probiotics or synbiotics on body weight, body mass index (BMI), and waist circumference in overweight and obese adults (BMI ≥â 25 kg/m2). DATA SOURCES: Five electronic databases-PubMed, Embase, Cochrane Library/CENTRAL, LILACS, and Web of Science-were searched from inception to August 2017. No language restrictions were applied. STUDY SELECTION: Randomized and quasi-randomized parallel trials that assessed the effects of oral supplementation with probiotics or synbiotics vs any other intervention but bariatric surgery or fecal transplantation in overweight or obese adults were selected. DATA EXTRACTION: Three teams of 2 authors independently assessed risk of bias and extracted data from the included trials. Data were pooled using inverse-variance random-effects meta-analyses. The quality of evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. RESULTS: Nineteen randomized trials (28 publications, 1412 participants) were included. There were no differences in mean body weight change [mean difference (MD), -0.54 kg; 95%CI, -1.09 to 0.01; I2 = 0%; moderate quality of evidence) or mean BMI change (MD, -0.19 kg/m2; 95%CI, -0.43 to 0.04; I2 = 51%; low quality of evidence) between groups who received probiotics or synbiotics and control groups. Oral supplementation with probiotics or synbiotics reduced mean waist circumference compared with control (MD, -0.82 cm; 95%CI, -1.43 to -0.21; I2 = 46%; low quality of evidence). CONCLUSIONS: The findings suggest that oral supplementation with probiotics or synbiotics has a small effect to reduce waist circumference but no effect on body weight or BMI, although the quality of evidence is low to moderate. Therefore, the current evidence is not definitive. Large-scale trials are needed and may help to better inform clinical practice. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration number CRD42018075126.