Obesity brought on by a high-fat diet might be accompanied by changes in gut bacteria that alter brain chemistry in such a way as to promote anxiety and depression.
gut bacteria in pink

This was the conclusion that researchers from the Joslin Diabetes Center of Harvard Medical School in Boston, MA, and colleagues came to after studying the link between gut microbes and brain function in mice with diet-induced obesity.

They report their findings in a paper that is now published in the journal Molecular Psychiatry.

In the paper, they note how giving the animals antibiotics — which changed the composition of their gut bacteria — reduced inflammation, improved "insulin signaling in the brain," and reduced "signs of anxiety and depression."

"What this study says," says senior study author C. Ronald Kahn, a professor of medicine at Harvard University and co-head of the Section on Integrative Physiology and Metabolism at Joslin Diabetes Center, "is that many things in your diet might affect the way your brain functions, but one of those things is the way diet changes the gut bacteria or microbes."

Obesity, diabetes, and gut microbes
Obesity and diabetes are serious public health problems across the globe. Since 1975, worldwide prevalence has almost tripled. Global figures for 2016 estimate that around 650 million people, or 13 percent of the world's population, are obese.

Much of this obesity epidemic is fuelled by diets that are high in fat and "energy-dense foods," along with reductions in physical activity.

Global rates of diabetes have also risen significantly in the past 30 years. In 1980–2014, they rose from 108 to 422 million.

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