Obesity: Study Finds Intestinal Bacteria May Cause Weight Gain

A recently-released study on mice (led by Andrew Gewirtz at Emory University) concludes that your intestines harbor a universe of bacteria - the so-called gut microbiota - that may play an important role in whether your body will store the food you eat as extra pounds.

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The authors explain in their paper (published in Science Express) the cause that may account for the extra weight. Inflammatory signaling can promote a condition called metabolic syndrome, which causes weight gain, high blood pressure and high cholesterol levels, and a higher risk for developing diabetes and heart disease.

Fatter mice were bred for the study, to lack a protein known as toll-like receptor 5 (TLR5).

The job of TLR5 is to control the mass of pathogens living in the intestine; without it, the normally harmless gut bacteria tend to over flourish and increase in number. When these bugs proliferate, it triggers an inflammatory state as the body attempts to respond to the increasing population of bugs, and at the same time makes cells less sensitive to insulin.

Inflammatory factors and insulin compete for the attention of the same intestinal cells; if the cells are busy responding to inflammatory factors, then they are less likely to take up glucose and process it effectively. This desensitization to insulin and glucose then leads to the symptoms of metabolic syndrome, such as weight gain, high cholesterol and triglyceride levels and elevated blood pressure - which were all present in the TLR5-deficient mice.

So, what causes changes in gut microbiota? Many things, says Gewirtz, including the use of antibiotics, cleaner water and improved sanitation and hygiene in general, which influences the type and amount of microbes that reside in the intestines.

In the absence of TLR5, the community of microbes in your gut changes and, as Gewirtz says, "when the intestinal bacteria is changed, the host response changes with them, and that may predispose you to a variety of diseases of which obesity and metabolic syndrome are perhaps the most mild."

Further studies still need to be done to find out exactly what and how the TLR5 and/or gut bugs can be changed for positive outcomes for humans (especially as it applies to obesity), but this is certainly a very promising study.

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