Relationship Between The Gut Microbiota And Obesity, Exercise Habits And Physical Fitness In Young Children

PURPOSE: The gut microbiota changes daily depending on lifestyle habits such as diet, exercise, and sleep, stress, and aging, resulting in large individual differences. To examine the relationship between the gut microbiota and exercise habits and physical fitness in young children, fecal concentrations of Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria and Firmicutes/Bacteroidetes ratio were analyzed in young children. METHODS: The subjects were 54 young children (21 male, 33 female) aged 4 years. Obesity was determined upon an obesity index score ((real weight - standard weight) / standard weight×100) of more than +15%. We administered physical tests comprising seven types of exercises (grip strength, standing long jump, softball throw, 25-m run, side-step, upright hand standing time, and sitting trunk flexion) to gauge the children’s state of physical fitness. We carried out a questionnaire survey regarding the children’s exercise habits. Relative gut microbiota composition was determined by analyzing DNA extracted from stool samples using a quantitative polymerase chain reaction that specifically measured the quantity of a target gene (16S rRNA). The items to be detected were diversity, phylum composition, bifidobacteria, lactic acid bacteria, and Firmicutes to Bacteroidetes (F/B) ratio. RESULTS: The phylum composition of Bacteroidetes, Firmicutes, Actinobacteria and Proteobacteria in 54 young children were 42.3 ± 7.1%, 44.4 ± 7.0%, 7.8 ± 3.6% and 5.0 ± 3.3%. There were no gender differences in diversity, phylum composition, bifidobacteria, lactic acid bacteria, and F/B ratio. The obtained data indicate that obese children have a significantly higher level of Firmicutes and lower level of Bacteroidetes compared to non-obese children (p < 0.05). The F/B ratio was higher in obese children compared with non-obese subjects (p < 0.05). It was shown that young children with exercise habits had lower F/B ratio, and higher lactic acid bacteria than the group without the habits (p < 0.05 for all). The gut microbiota profiles showed no relationship with physical fitness. CONCLUSIONS: It was shown that obesity and habitual exercise may affect gut microbial properties in young children. Supported by Grant-in-Aid for Scientific Research (C) (No.21 K11585) from Japan's Ministry of Education, Culture, Sports, Science and Technology