The sterile gut of a newborn baby is quickly populated by a variety of different microbes, yet both acquisition and development of this microbial community is poorly understood. Recently, much attention has been given to findings that indicate gut microbiota - the body's microbial ecosystem - may play a role in several diseases, including obesity, type 2 diabetes, steatosis, cardiovascular diseases, and inflammatory bowel disease.

You can add obesity to the list. Research published today in PLOS Computational Biology found the composition of microbiota in a newborn baby's gut has been linked to the rate of early infant growth. Further, these findings support assertions that early development of gut microbiota, essential to human health throughout life, can impact the likelihood of obesity.

The study, conducted by Dr. Merete Eggesbo and associates at the Norwegian Institute of Public Health, took data from infants when they were four, 10, 30 and 120 days old. By looking at fecal samples from 218 babies, statisticians Richard White and Shyamal Peddada developed a method to identify the points and periods in time when detection of specific bacterial groups was associated with an infant's development. Their research showed that detection of Bacteroides species at day 30 in males was significantly associated with reduced growth. By contrast, presence of the E. coli species from four to 30 days after birth was observed to correspond with expected growth in both male and female infants.

"We have created a new way of looking at the development of gut microbiota over time and relating this development to health outcomes," said the authors. "This is useful to the scientific community as it is difficult to characterize, in a meaningful way, how the gut develops over time."

Having mapped part of infant gut microbiota using broad and unspecific probes only, the authors cautioned that observed associations may be markers for other alterations in the gut microbiota composition. It is also possible that other factors could give rise to such associations, for which the study may not have been large enough to adequately control. However, the researchers believe their method can prove a useful tool for studying this topic further.

"I have great hopes that in the future we will be able to manipulate gut microbiota and thereby both prevent and cure disease," writes Eggesbo in an email. "However that is a long way down the road! First we need to understand how everything works together."

"Our method should have wide future applicability for studying gut microbiota, and is particularly important for translational considerations, as it is critical to understand the timing of microbiome transitions prior to attempting to manipulate gut microbiota in early life," stated the authors. In the future, researchers believe non-invasive manipulation of gut microbiota composition in early infancy could offer a new approach to manage childhood obesity and associated disorders.

The Centers for Disease Control and Prevention (CDC) defines obesity as having excess body fat, whereas overweight is defined as having excess body weight for a particular height from fat, muscle, bone, water, or a combination of these factors. Both overweight and obesity are the result of "caloric imbalance" - too few calories expended for the amount of calories consumed - and may be affected by genetic, behavioral, and environmental factors. In the past 30 years, childhood obesity has more than doubled in children and tripled in adolescents, according to the CDC. In 2010, more than one-third of children and adolescents in the US were overweight or obese.

"Some obesity trajectories are set early in life, with rapid weight gain being a risk factor for later development of obesity," said the authors. "We expanded the biological literature by reporting time-dependent patterns associated with expected growth."

Alternative Studies

Unlike the authors of the Norwegian study, many other investigators of obesity in children have focused on lifestyle factors more so than those of a biological nature. One case in point: an unrelated study, published in the March/April issue of the Canadian Journal of Public Heath, delved into both perinatal and childhood factors to determine risk factors for obesity in young Canadian children.

The authors of the study assessed data from a nationally representative sample of children aged 6 to 11 years in the Canadian Health Measures Survey in order to assess the potential of various early-life factors and their association with obesity among young Canadian children. Next, they evaluated potential associations of perinatal and early childhood behaviors and socio-economic factors.

Of 968 term-born children, 21 percent were overweight and another 13 percent were obese. Maternal smoking during pregnancy was positively associated with obesity. This association was mediated by birth weight (suppression effect); once controlled, the strength of the association between smoking and child obesity increased by 12 percent. Exclusive breastfeeding for six months, adequate sleep hours, and being physically active were found to be protective. Breastfeeding, whether exclusive or not, significantly reduced obesity risk among children whose mothers never smoked in pregnancy.

Population attributable risk fractions indicated that 24.4 percent, 11.5 percent, 11.3 percent and 6.0 percent prevalent cases of child obesity might be prevented by exclusive breastfeeding, smoking cessation during pregnancy, adequate sleep during childhood, and avoiding high birth weight, respectively.

Authors Yipu Shi, Margaret de Groh, and Howard Morrison concluded that effective prevention strategies targeting four modifiable maternal and child risk factors may reduce childhood obesity by up to 54 percent in Canada.