Childhood obesity risk factors occur before birth

New research suggests the mother's gut bacteria and its interactions with immune cells and metabolic organs, including fat tissue, play a key role in childhood obesity. Childhood obesity is a complex disease. It isn't just a cosmetic issue; obesity involves an excessive amount of body fat that comes with serious medical concerns like increased risk of diseases and health problems.

In the United States, the number of children and adolescents affected by obesity has more than tripled since the 1970s, according to the Centers for Disease Control and Prevention. Obesity is increasing at an alarming 2.3% rate each year among school-aged children.

Early life decisions and their role in a child's health 

Scientists at Wake Forest Baptist Health explored the role of gut bacteria in childhood obesity. The goal of the study was to determine whether certain early life decisions impact the child's health. The authors said they hope to encourage future research and to help parents, physicians, and health care agencies make informed decisions to decrease the likelihood of obesity. 

The review identified potential risk factors for childhood obesity based on the evidence of gut microbial imbalances, elevated body mass index (BMI), and increased risk for type 2 diabetes, among other factors. 

"The medical community used to think that obesity was a result of consuming too many calories. However, a series of studies over the past decade has confirmed that the microbes living in our gut are not only associated with obesity but also are one of the causes," said Hariom Yadav, Ph.D., lead author of the review and assistant professor of molecular medicine at Wake Forest School of Medicine, part of Wake Forest Baptist.

The study, published in the current issue of the journal Obesity Reviews, looked at existing animal and human studies to examine the relationship between gut microbiome and immune cells. The researchers studied how this interaction can pass from mother to baby as early as gestation as well as how it can contribute to childhood obesity.

The review also described how a mother's health, diet, exercise level, antibiotic use, birth method, and feeding method can affect the risk of obesity in her children.

“I was surprised to see very few very planned studies are done to establish microbiome-immune-metabolic connection, especially for childhood obesity, that opens doors for tremendous research opportunities,” Yadav told NutraIngredients-USA.

Indeed, it research suggests obesity begins even before birth. Many factors from as early as gestation may very well contribute to obesity. 

Birth method 

The researchers said it appears that infants born by C‐section have a higher risk of developing childhood obesity compared to babies who are vaginally delivered.

“The gut microbiome of infants born vaginally harbor the bacteria of maternal birth canal and vagina, which are typically beneficial bacteria. In contrast, the gut of infants born through Cesarean‐section (C‐section) is relatively populated by bacteria from maternal skin,” according to the report. 

Feeding method

Formula-fed babies have higher incidences of childhood obesity and harbor different gut microbiomes versus infants who are breastfed. This suggests that early‐life feeding method impact the risk of childhood obesity. Human milk oligosaccharides (HMOs) from breastmilk promote healthy bacteria in the infant's gut. 

Antibiotics

Antibiotics significantly decrease the diversity of the gut microbiome. When mothers take antibiotics before and/or during pregnancy, infants only receive a partial set of bacteria from the mother rather than a fully diverse healthy microbiome. This can lead to potential obesity. 

Taking antibiotics during infancy and early childhood also significantly increases the risk of childhood obesity by inducing abnormal gut changes and affecting normal functioning of microbiome‐associated metabolism regulation and immune system. These early life processes which regulate obesity cause the gut microbiome, immune, and metabolic functions to mature.

Maternal weight

According to the report, nearly two‐thirds of American child‐bearing aged women are obese.

The study stated that the gut microbiome is significantly less diverse in children with obese mothers, which demonstrates that environmental factors like microbiome may contribute to human childhood obesity. 

The research suggests that maternal health is crucial for the risk of obesity in offspring later in life. Additional factors such as  diabetes, malnutrition, medications, and lifestyle (during, before, and after pregnancy) can also impact the offspring's microbiome immune metabolic axis (MIM). 

“Maternal obesity and diabetes are known to pose high risks of developing these ailments in their children. This is supported by the facts that: (i)mothers with obesity/diabetes even before pregnancy (prepartum) have increased expression of harmful genes in reproductive cells including ovum, that are imprinted and passed to the offspring; (ii) mothers who become obese or diabetic during pregnancy (peripartum) can induce gene imprinting in the developing embryonic cells; (iii) mothers with obesity/diabetes can pass harmful metabolites through placental barriers that can influence the risk of obesity and diabetes in offspring; (iv) mothers that develop obesity soon after delivery (postpartum) can also pass harmful metabolites, fat, proteins and bacteria through breastmilk to the offspring, impacting the MIM axis. Thus, prepartum, peripartum, intrapartum and postpartum health of the mother can impact the risk of obesity in offspring.”

Do fathers play a role in childhood obesity?

Yadav told NutraIngredients-USA that it is an interesting question. “While searching literature, we couldn’t find much evidence of paternal microbiome effects on childhood obesity. Although, there were reports, but very few and superficial studies, so this remains an area of intense research. This was surprising for me.”

The researchers add that further studies are needed to investigate factors that can influence the risk of obesity. In addition, having a better understanding of the role of the gut microbiome and obesity in both mothers and their children hopefully will help scientists design more successful preventive and therapeutic strategies to check the rise of obesity in children, Yadav said.

Identifying the gaps in research

"This compilation of current research should be very useful for doctors, nutritionists and dietitians to discuss with their patients because so many of these factors can be changed if people have enough good information. We also wanted to identify gaps in the science for future research."

Yadav told NutraIngredients-USA that he and his team are actively conducting studies on microbiome-immune-metabolic interactions.

Source: Obesity Reviews 2019;1–13. https://doi.org/10.1111/obr.12963
Microbiome‐immune‐metabolic axis in the epidemic of childhood obesity: Evidence and opportunities
Authors: HJ Kincaid, et al.