While in rich countries, one in three children is overweight, identifying early indicators of obesity in young children could allow preventive measures to be taken against obesity. However, oral bacteria could hold a key to obesity or rather a signature of future risk, concludes this research presented in Scientific Reports. From this work by the "Penn State", which shows that the composition of the oral microbiota or the micro-organisms residing in the mouth of children aged 2 years can predict their weight gain, emerges the prospect of a simple saliva test making it possible to predict the risk of obesity later in life.
Because the trajectories of weight gain during infancy are well linked to the composition of the oral microbiota and the presence of certain bacterial communities, in children aged 2 years, which suggests the possibility of an early indicator of obesity .
Exploring the relationship between microbiota and weight gain: this trial, INSIGHT, involves 300 children with the objective of looking at whether and how appropriate parental intervention at the start of life can prevent the development of obesity. The trial is also designed to identify biological and social risk factors for obesity. It identifies a child's oral microbiota as linked to weight gain during the 2 years following birth: the digestive tract is inhabited by a variety of microorganisms, including beneficial bacteria, which contribute to digestion and immunity. This gut microbiotais modified by changes in diet and can vary considerably between individuals. Some variations in the gut microbiota have been associated with obesity in some adults and adolescents, but the relationship with weight gain has never been explored. Finally, the oral microbiota is generally studied in relation to periodontal disease, and periodontal disease has been linked, in some cases, to obesity.
Sarah Craig, a postdoctoral researcher in biology at Penn State and her team explored all possible direct associations between the oral microbiota and weight gain in 226 children. Data analysis finds that:
- the oral microbiota of children who have gained weight rapidly is less diversified with therefore fewer distinct bacterial communities;
- in the oral microbiota of children who gained weight rapidly, the Firmicutes/Bacteroidetes ratio, 2 of the most common groups of bacteria found in the human microbiota, is higher; this ration constitutes a distinctive signature of the risk of obesity;
- weight gain in children is also linked to the diversity of the mother's oral microbiota: this could reflect a genetic predisposition of the mother and child to a similar microbiota, or a similar diet and environment for the mother and the child.
Good health is also a great diversity of the intestinal microbiota : “This great diversity helps protect against inflammation or harmful bacteria and is important for the stability of digestion in the face of changes in diet or environment. There is also a certain balance between these 2 bacterial groups, Firmicutes and Bacteroidetes. Disturbances of this balance can lead to dysregulation of digestion”.
Obesity is signed earlier in the oral microbiota than in the gut microbiota: Lower diversity and a higher Firmicutes to Bacteroidetes (F/B) ratio in the gut microbiota have already been observed in adults and adolescents suffering from obesity. However, here the researchers did not identify a relationship with weight gain, suggesting that the gut microbiota of the 2-year-old child may not be fully established. The results thus suggest that obesity may be signed earlier in the oral microbiota than in the intestinal microbiota.
If these data were confirmed, it would be possible to develop an oral test for detecting the risk of obesity, a very interesting prospect when oral samples are very simple to perform.