When anxiety strikes, many of us reach out for junk food—a chocolate bar for an afternoon boost or a donut to reward ourselves after a long day. But here’s the twist: research from the University of Colorado Boulder reveals that indulging in fatty foods might actually fuel our anxiety. Their study found that a high-fat diet messed with the gut bacteria in mice, triggering changes in brain chemicals that ramp up anxiety.
“Everyone knows that these [high-fat foods] are not healthy foods, but we tend to think of them strictly in terms of a little weight gain,” said lead author Professor Christopher Lowry. Health organisations advise women to eat no more than 20g of saturated fat a day and men no more than 30g, or about 11% of our daily calories from food. However, many people in the UK consume more than this and according to the US Centers for Disease Control, the average diet contains around 36% fat. (Also read: From cutting carbs to fad diets: Debunking most popular nutrition myths and misconception for optimal health )
High-Fat Diets: More Than Just Weight Gain
The researchers split the teenage rats into two groups and looked at how this affected their mental health. For nine weeks, one group ate a typical diet with 11% fat and the other a high-fat diet with 45% fat. The scientists collected faecal samples to assess gut flora during the study, which was published in the journal Biological Research. At the end of the study, tests were carried out to see if the diet had any effect on the participants’ behaviour. The rats on the high-fat diet were obviously heavier than those in the other group, but their gut microbiomes were also significantly less diverse. Specifically, they had significantly more bacteria from the Firmicutes category and much less from the Bacteroidetes group.
Genetic Changes and Anxiety
In addition, three genes linked to serotonin synthesis showed increased activity in the high-fat group. Although serotonin is often associated with positive emotions, research has shown that when it activates certain neurons, it can also cause anxiety-like symptoms. Tryptophan hydroxylase, or tph2, is one of three genes also linked to mood problems and an increased risk of suicide in people.
“It’s amazing to think that a high-fat diet alone can change the way these genes are expressed in the brain,” Professor Lowry said. “The brains of the high-fat group essentially had the molecular signature of a high anxiety state.” Although it’s not proven, Professor Lowry believes that an unhealthy microbiota damages the stomach lining, which is why a high-fat diet could contribute to anxiety. This could allow germs to enter the bloodstream and eventually communicate with the brain via the vagus nerve, which runs from the digestive system to the brain.
“It makes sense if you think about human evolution,” he remarked. “To prevent disease in the future, we are hardwired to really notice things that make us sick.” He also mentioned that not all fats are bad and that some studies have shown that healthy fats, such as those from avocados, can offset unhealthy fats, such as those from burgers. In addition, omega-3 fatty acids, found in nuts, seeds, olive oil and seafood, have anti-inflammatory and cognitive benefits.
