Effects of Synbiotic Supplement on Human Gut Microbiota, Body Composition and Weight Loss in Obesity

Abstract

Targeting gut microbiota with synbiotics (probiotic supplements containing prebiotic components) is emerging as a promising intervention in the comprehensive nutritional approach to reducing obesity. Weight loss resulting from low-carbohydrate high-protein diets can be significant but has also been linked to potentially negative health effects due to increased bacterial fermentation of undigested protein within the colon and subsequent changes in gut microbiota composition. Correcting obesity-induced disruption of gut microbiota with synbiotics can be more effective than supplementation with probiotics alone because prebiotic components of synbiotics support the growth and survival of positive bacteria therein. The purpose of this placebo-controlled intervention clinical trial was to evaluate the effects of a synbiotic supplement on the composition, richness and diversity of gut microbiota and associations of microbial species with body composition parameters and biomarkers of obesity in human subjects participating in a weight loss program. The probiotic component of the synbiotic used in the study contained Lactobacillus acidophilus, Bifidobacterium lactis, Bifidobacterium longum, and Bifidobacterium bifidum and the prebiotic component was a galactooligosaccharide mixture. The results showed no statistically significant differences in body composition (body mass, BMI, body fat mass, body fat percentage, body lean mass, and bone mineral content) between the placebo and synbiotic groups at the end of the clinical trial (3-month intervention, 20 human subjects participating in weight loss intervention based on a low-carbohydrate, high-protein, reduced energy diet). Synbiotic supplementation increased the abundance of gut bacteria associated with positive health effects, especially Bifidobacterium and Lactobacillus, and it also appeared to increase the gut microbiota richness. A decreasing trend in the gut microbiota diversity in the placebo and synbiotic groups was observed at the end of trial, which may imply the effect of the high-protein low-carbohydrate diet used in the weight loss program. Regression analysis performed to correlate abundance of species following supplementation with body composition parameters and biomarkers of obesity found an association between a decrease over time in blood glucose and an increase in Lactobacillus abundance, particularly in the synbiotic group. However, the decrease over time in body mass, BMI, waist circumstance, and body fat mass was associated with a decrease in Bifidobacterium abundance. The results obtained support the conclusion that synbiotic supplement used in this clinical trial modulates human gut microbiota by increasing abundance of potentially beneficial microbial species.

Keywords: body composition; gut microbiota; obesity; obesity biomarkers; prebiotic; probiotic; synbiotic; weight loss.

Figure 1

Mean relative abundance (%) of phyla (A) and genera (B) by the treatment groups and time points.

Figure 2

Changes in the relative microbial abundance in the gut after synbiotic intervention. * p < 0.05, ** p < 0.01, *** p < 0.001, as compared with the placebo group at the end of the trial.

Figure 3

Observed species (A), Chao1 diversity (B) and Shannon diversity (C) plotted by the treatment group and time point. The box spans the first and third quartiles. A horizontal line marks the median and the whiskers represent ±1.5 times the interquartile range. Outliers (panels A and B) are marked as individual points. Significant differences between groups were determined using the estimated marginal means analysis applied to linear mixed model, which was built with alpha diversity as the response variable, the treatment group and time points as predictor variables, and subject number as a random variable.

Figure 4

Principal Coordinates Analysis (PCoA) of unweighted UniFrac (A), weighted UniFrac (B) and Bray–Curtis dissimilarity data (C). The scatter plots show principal coordinate 1 (PC1) vs. principal coordinate 2 (PC2) with percentages of variation explained by the components indicated. The points are colored by the treatment group and time point.

Figure 5

Heatmap of associations between gut microbiota, body composition and metabolic parameters in the placebo (A) and synbiotic groups (B) at the end of trial. r values were calculated using Pearson’s linear correlation test; * p < 0.05, ** p < 0.01. Pearson’s r values below 0.30 or above −0.30 are not indicated. Red-brown color indicates negative correlation, blue-green color—positive correlation.