What is already known
Obesity is on the rise worldwide, affecting both adults and children, and increasing the risk of serious health problems such as diabetes, heart disease and cancer. Childhood obesity is especially concerning because it can lead to long-term health issues. Previous studies have shown that adults with obesity often have alterations in their gut bacteria, but it’s still unclear whether these changes are a cause or a result of obesity.
What this research adds
Researchers tracked 700 Danish children from birth to 10 years of age and found no link between early-life gut microbiota and later obesity, body composition, or body mass index (BMI) — which is often used as a proxy for obesity. While certain prenatal and early-life factors such as maternal BMI and birth size were associated with a child’s BMI, no relationship was found between specific bacterial species and obesity.
Conclusions
The findings suggest that the composition of the gut microbiota in early life is not a key factor in obesity risk.
Obesity is on the rise worldwide, affecting both adults and children, and increasing the risk of serious health problems such as diabetes, heart disease and cancer. Research has shown that adults with obesity often have alterations in their gut bacteria, but a new study found no link between early-life gut microbiota and later obesity, body composition, or body mass index (BMI) — which is often used as a proxy for obesity.
The findings, published in Med, indicate that the composition of the gut microbiota in early life may not be a key factor in obesity risk. Although the work does not rule out a relationship between the early microbiota and obesity, the researchers say, “it suggests that if such associations exist, they may be more complex and potentially influenced by factors emerging later in life, including lifestyle changes.”
Childhood obesity is especially concerning because it can lead to long-term health issues. Previous studies have shown that changes in the balance between two main types of bacteria in the human gut — Firmicutes and Bacteroidetes — are linked to obesity. However, it’s still unclear whether these changes are a cause or a result of the condition.
To study how microbiota in early life might influence obesity risk later in childhood,
Christina Egeø Poulsen at the University of Copenhagen in Denmark and her colleagues analyzed data from the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC2010) birth cohort, which tracks 700 Danish children from birth to age 10.
Obesity risk
In the COPSAC2010 study, children had their BMI measured at several time points between 1 week and 10 years of age. By age 10, 19% of the children were overweight, 7% were obese and 47% had an early adiposity rebound — a phenomenon where children gain fat rapidly at a younger age, which is often linked to obesity later on. The study also examined the gut microbiota at five time points — 1 week, 1 month, 1 year, 4 years and 6 years — as well as body composition at age 6.
While certain prenatal and early-life factors, including a child’s birth size, were associated with BMI, the analysis showed no links between the diversity of gut microbiota in the first years of life and later obesity or adiposity rebound.
However, higher gut microbiota diversity at 1 week and 6 years was associated with lower body fat and higher lean mass at age 6. Gut microbiota composition at 1 week, 1 month and 1 year had some modest association with BMI and body composition at age 10.
Minimal influence
Next, the researchers analyzed the ratio of Firmicutes and Bacteroidetes as well as other bacterial species that have been linked to obesity in previous studies. They found no significant associations between any of these bacterial species and obesity.
Using a machine learning approach, the team also tried to predict BMI at age 10 based on early-life gut microbiota composition. While the model was accurate when tested on the training dataset, it failed to predict BMI outcomes in data it had never encountered before.
The results suggest that early-life gut microbiota has minimal influence on obesity risk, and factors such as maternal BMI and birth size play a larger role. The findings also indicate that obesity may alter the gut microbiota over time rather than being caused by it, the authors say.
