It wasn’t long ago that conventional medicine debated the existence of the gut-brain axis, the connection that links your emotions, intestines and brain.

The medical community couldn’t dispute it for long, however, given that about 90 percent of serotonin, a chemical that sends messages from one side of the brain to the other, is produced in the human gut.

Obesity and diabetes are serious conditions that harm many parts of your health, including your gut. (Remember, gut health problems could be a warning sign of type 1 diabetes?)

Eating a high-fat diet, a direct contributor to obesity and diabetes, creates greater emotional problems and direct shifts in the makeup of bacteria in the gut too, according to findings from the Joslin Research Center (affiliated with Harvard Medical School).

In their work with mice, Joslin researchers had long studied the damage done by diabetes, obesity and other metabolic health problems in their work with mice fed high-fat diets.

One variable stood out in their previous research: Obese mice that had been fed high-fat diets showed far more signs of emotional problems (depression, anxiety and obsessive behaviors) than animals fed healthier diets.

For their newest study, researchers took a different approach by giving mice behavioral tests commonly used to screen drugs for depression and anxiety. They learned mice that were fed high-fat diets experienced greater amounts of depression and anxiety.

However, when scientists took steps to change the gut health makeup of obese mice by giving them antibiotics their emotional health improved.

Taking that gut bacteria shift one step further, Joslin research also discovered the gut microbiomes of obese mice triggered emotional problems when they were transplanted in germ-free mice. And other germ-free mice that received gut bacteria from obese mice given antibiotics showed no signs of emotional problems either.

Where the gut-brain link really came into play was when researchers examined parts of the brain that govern metabolism and emotions, according to Dr. C. Ronald Kahn, Chief Academic Officer who leads the Section on Integrative Physiology and Metabolism at Joslin.

Like other tissues, these areas of the brain became insulin-resistant in test animals fed high-fat diets and this resistance was mediated partly by their microbiomes, Dr. Kahn said.

The Joslin team also found alterations in the gut health of mice were linked to the production of some chemicals that send signals across the brain too.

Now, scientists are studying specific populations of bacteria involved in the gut-brain axis that may govern this process, with an eye on creating healthier metabolic profiles in the brain.

Interestingly, Dr. Kahn points out the problems of using antibiotics as “blunt tools that change many bacteria in very dramatic ways.”

“Going forward, we want to get a more sophisticated understanding about which bacteria contribute to insulin resistance in the brain and other tissues. If we could modify those bacteria, either by putting in more beneficial bacteria or reducing the number of harmful bacteria, that might be a way to see improved behavior.”

Fortunately, there’s a growing body of evidence that shows probiotics like EndoMune Advance Probiotic may be a safe and proven tool for treating behavioral issues among mice and humans and provide some extra help to fight obesity too.