Relationship between the gut microbiota and obesity in children and adolescents

Abstract

Objectives Obesity is considered as one of the most important public health problems of our times. The last few decades the prevalence of obesity, especially among children and adolescents, has increased dramatically worldwide. The aim of our study was to determine whether the composition of the gut microbiota is related to obesity in childhood.

Methods A cross-sectional study was set-up to examine the gut microbiota using faecal samples from 22 obese children and 33 non-obese children aged 6 – 16 years. The microbial composition in the faecal samples was analyzed by quantitative plating for Staphylococcus spp., Bacteroides fragilis group, Clostridium spp., Lactobacillus spp. and for Bifidobacterium spp.; matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for identification of species of the Bacteroides fragilis group and quantitative real-time polymerase chain reaction (qRT-PCR) to determine the number of Staphylococcus spp., Bacteroides-Prevotella-Porphyromonas group, Clostridium coccoides-Eubacterium rectale group, Clostridium leptum subgroup, Lactobacillus spp., and Bifidobacterium spp. For statistical analysis, the BMI z-score was used as dependent variable thereby correcting for age and gender. A P-value of <0.05 was considered statistically significant.

Results Both quantitative plating and qRT-PCR showed that the faecal concentration of the Bacteroides fragilis group in obese children was significantly lower than in non-obese children (P = 0.017 and 0.018, respectively). Additionally, MALDI-TOF MS analysis demonstrated that obese children were colonized more frequently with B. fragilis than non-obese children (19.18% and 7.33%, P = 0.039) whereas colonization with B. vulgatis was significantly higher in non-obese children compared to obese children (8.14% and 18.91%, P = 0.016). Furthermore, B. fragilis was significantly positively correlated to the BMI z-score (P = 0.03). Higher colonization with B. fragilis could therefore be associated with an increase in weight. The microbiota of obese children was also associated with a higher Firmicutes/Bacteroides ratio (P = 0.02).

Conclusions Significant differences were found in the composition of the fecal microbiota of obese and non-obese children. These results indicate that changes in the gut microbiota during childhood and adolescence could lead to the development of obesity and that the gut microbiota could be an additional risk factor for obese-prone children.