Plain language summary
The gut microbiota plays a role in the development of obesity and associated diseases. Whilst energy-restricted, low-carbohydrate, high-protein diets can facilitate substantial weight-loss, they also have been linked to ill-effects and unfavourable changes in the gut microbiota from excess protein fermentation. Pro-and prebiotics (synbiotics) have become a promising intervention in the management of obesity. This small placebo-controlled clinical trial involved 20 obese adults following an energy-restricted (approx.950 kcal/day) low-carbohydrate, high-protein diet. The study examined whether a supplementary synbiotic contributed to additional changes in body composition and metabolic biomarkers. The synbiotic contained Lactobacilli spp. and Bifidobacteria spp. and a prebiotic mixture of galactooligosaccharides. Overall, at the end of the 3-month trial, there was no remarkable difference between the groups. Both experienced a significant and decreasing trend in body mass, waist circumference, body mass index, fat mass, fat percentage, and glucose level, affirming the known benefits of the described weight-loss diet. However, the synbiotic supplementation group had a greater decrease in HbA1C and significant alterations in gut microbiota, showing an increased abundance of gut bacteria associated with positive health effects. Due to the complexity of microbial species and host interactions, the authors advocate for more research to identify their significance and shed light on contradictory findings. This study identified that synbiotics may not contribute to additional changes in body composition when combined with an energy-restricted, low-carbohydrate, high-protein diet but they can offer additional health benefits by inducing favourable changes to the gut microbiota.
undefined: 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 , , , and 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 and , 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 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 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.