Impact of bacterial probiotics on obesity, diabetes and non-alcoholic fatty liver disease related variables: a systematic review and meta-analysis of randomised controlled trials.

Objective: To systematically review the effect of oral intake of bacterial probiotics on 15 variables related to obesity, diabetes and non-alcoholic fatty liver disease.

Design: Systematic review and meta-analysis.

Data Sources: Medline, EMBASE and COCHRANE from 1990 to June 2018.

Eligibility Criteria: Randomised controlled trials (≥14 days) excluding hypercholesterolaemia, alcoholic liver disease, polycystic ovary syndrome and children <3 years.

Results: One hundred and five articles met inclusion criteria, representing 6826 subjects. In overweight but not obese subjects, probiotics induced improvements in: body weight (k=25 trials, d=-0.94 kg mean difference, 95% CI -1.17 to -0.70, I²=0.0%), body mass index (k=32, d=-0.55 kg/m², 95% CI -0.86 to -0.23, I²=91.9%), waist circumference (k=13, d=-1.31 cm, 95% CI -1.79 to -0.83, I²=14.5%), body fat mass (k=11, d=-0.96 kg, 95% CI -1.21 to -0.71, I²=0.0%) and visceral adipose tissue mass (k=5, d=-6.30 cm², 95% CI -9.05 to -3.56, I²=0.0%). In type 2 diabetics, probiotics reduced fasting glucose (k=19, d=-0.66 mmol/L, 95% CI -1.00 to -0.31, I²=27.7%), glycated haemoglobin (k=13, d=-0.28 pp, 95% CI -0.46 to -0.11, I²=54.1%), insulin (k=13, d=-1.66 mU/L, 95% CI -2.70 to -0.61, I²=37.8%) and homeostatic model of insulin resistance (k=10, d=-1.05 pp, 95% CI -1.48 to -0.61, I²=18.2%). In subjects with fatty liver diseases, probiotics reduced alanine (k=12, d=-10.2 U/L, 95% CI -14.3 to -6.0, I²=93.50%) and aspartate aminotransferases (k=10, d=-9.9 U/L, 95% CI -14.1 to -5.8, I²=96.1%). These improvements were mostly observed with bifidobacteria (, ), subsp and lactobacilli (, , ) containing mixtures and influenced by trials conducted in one country.

Conclusions: The intake of probiotics resulted in minor but consistent improvements in several metabolic risk factors in subjects with metabolic diseases.

Trial Registration Number: CRD42016033273.