Katherine Xiu

In tackling America’s childhood obesity epidemic, Yale scientists are zooming in close, investigating how the condition could be linked to microscopic communities of gut bacteria.

Nicola Santoro, a pediatrics researcher at the Yale School of Medicine, has led a study that suggests obesity is related not only to the food we eat but also the microbes that process it. The study, which was published in the Journal of Clinical Endocrinology & Metabolism on Sept. 20, showed for the first time that gut flora composition is linked to fat distribution in children and adolescents and that the digestive tracts of obese children have a “higher relative abundance of bacteria capable of fermenting carbohydrates” than their peers. As a result, obese children not only have different communities of gut flora, but these microbes can oxidize carbohydrates into storable fat at a much faster rate.

“We found that differences in gut flora distribution were marked between lean and obese children,” Santoro said.

His team analyzed the gut flora of 84 young people, 72 of whom had BMIs on the obesity spectrum, by extracting bacterial DNA from stool samples. Study participants kept food diaries, and resonance imaging was used to determine their body fat distributions.

Using this data, the researchers identified six microbe families whose presence was closely associated with obesity and subsequently determined that these groups displayed an increased ability to ferment fructose.

The study represented a new frontier for Santoro, who noted it was his “first time ever” doing research on microorganisms within the body. Santoro began researching childhood obesity over ten years ago during his residency at the Second University of Naples and moved to the United States to pursue this research further.

Despite the study’s positive results, Santoro acknowledged that there are still many answers left to find. In particular, Santoro said it is still unclear whether humans can actually change their microbiota and leverage the change to lose or gain weight.

While Santoro noted that the immediate practical implications of the study on obesity treatment aren’t yet clear, he said the study represented progress in obesity research related to the microbiome.

“We’re starting to unravel the kind of connections that I think in the long run can really help us understand how we fight obesity,” Santoro said.

Microbiome research itself is what senior Yale School of Medicine researcher Li Wen calls a “young, fast-moving field.” Twenty years ago, very little was known about the trillions of microbes that inhabit the digestive tract.

The National Institutes of Health launched the Human Microbiome Project in 2008 to more comprehensively document these species and, in the years since, research on gut flora has expanded dramatically, Wen said.

“This field has been expanding a lot, progressing to studies on obesity and the whole spectrum of disease, including psychiatric disorders,” Wen added.

However, she noted that microbiome research is still a developing field, adding that although researchers are uncovering the close association of the microbiome to diseases, the precise mechanisms of these relationships are not yet known.

Santoro said he is now seeking the specifics of the relationship between flora and body in the case of child obesity. He added that his team is now looking beyond fat composition to the way humans process energy.

“The next step is really to look at the interactions between microbiota metabolisms and the human metabolism,” Santoro said.

Childhood obesity has affected 12.7 million American children in the last decade alone, according to the Centers for Disease Control and Prevention.