Obesity and the Human Microbiome

Ruth E. Ley


Curr Opin Gastroenterol. 2010;26(1):5-11. 

In This Article

Abstract and Introduction


Purpose of review Obesity was once rare, but the last few decades have seen a rapid expansion of the proportion of obese individuals worldwide. Recent work has shown obesity to be associated with a shift in the representation of the dominant phyla of bacteria in the gut, both in humans and animal models. This review summarizes the latest research into the association between microbial ecology and host adiposity, and the mechanisms by which microbes in the gut may mediate host metabolism in the context of obesity.
Recent findings Studies of the effect of excess body fat on the abundances of different bacteria taxa in the gut generally show alterations in the gastrointestinal microbiota, and changes during weight loss. The gastrointestinal microbiota have been shown to impact insulin resistance, inflammation, and adiposity via interactions with epithelial and endocrine cells.
Summary Large-scale alterations of the gut microbiota and its microbiome (gene content) are associated with obesity and are responsive to weight loss. Gut microbes can impact host metabolism via signaling pathways in the gut, with effects on inflammation, insulin resistance, and deposition of energy in fat stores. Restoration of the gut microbiota to a healthy state may ameliorate the conditions associated with obesity and help maintain a healthy weight.


Up until the last few decades, obesity has been a rare physiological state. Now however, the number of obese or overweight humans has come to outnumber those suffering from malnutrition.[1] This is an unprecedented state for our species, resulting from a mismatch between our evolutionary biology and our modern environment. The human body is a complex system, made all the more complex through its interactions with the trillions of microorganisms that coat the body surface and densely populate the gut. Recent work has shown that the microbes of the gut may play a role in human metabolism and adiposity. Because they are environmentally acquired, microbes constitute one part of our environment that may contribute to the obese state. This review discusses the most recent findings and insights into the relationship between the human microbiota, obesity, and obesity-associated diseases.


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