Indulging in a dinner of steak as small as the palm of your hand and a side of fries can increase stress and increase the risk of anxiety, new research shows.
Researchers from the University of Colorado tested mice fed an average diet or a diet in which almost half of the daily calories came from fat found in junk food.
They found that the latter group had more active genes known to alter levels of the ‘feel good’ neurotransmitter serotonin, which had a direct impact on the mice’s increased anxiety.
Those who ate a high-fat diet also had less diversity in their gut bacteria, which helps with digestion and nutrient absorption and is known to benefit overall health.
Fat in burgers, steaks and fries is known to increase the risk of obesity, as well as damage to the blood vessels that supply the heart, and has been strongly linked to a range of health problems, including heart disease, digestive problems and diabetes. .
High-fat diets are known to increase the risk of obesity, heart disease and type 2 diabetes
The mice were monitored for nine weeks and divided into two groups: one group ate a diet that was 11 percent fat, while the other ate a diet with 45 percent fat, mainly saturated fat, the kind found in red meat.
Researchers collected stool samples and, after nine weeks, examined how the diets affected the mice’s behavior by dropping them into a maze from which they had to escape and placing them in a box separated by bright light and darkness. More time in the dark indicated more fear. behavior – and an open field to measure exploratory behavior and responses to a new environment.
Researchers then injected the mice with a short DNA chain that complements a particular genetic sequence to better understand how the genes involved in serotonin levels are activated.
By measuring that level of gene expression, researchers know how changes there affect serotonin function.
The group eating a high-fat diet not only gained weight, but also showed higher expression of three genes – tph2, htr1a and slc6a4 – all involved in the production and signaling of the neurotransmitter serotonin, which plays a role in both anxiety as well as depression.
These genes are particularly active in an area of the brainstem associated with stress and anxiety, indicating that higher expression may be associated with higher levels of those emotions.
The average American diet is about 36 percent fat, which amounts to about 80 to 120 grams of fat per day. A large portion of that daily amount of fat can come from eating a large portion of fries and an 8-ounce rib-eye steak.
The recommended calorie intake of 2,000 to 3,000 for the average American man, who weighs about 200 pounds, should come from macronutrients that include 45 to 65 percent carbohydrates, 10 to 35 percent protein and 20 to 35 percent fat.
For the average American woman who weighs about 170 pounds, it is recommended to consume about 2,000 calories per day, with a similar macronutrient breakdown.
The fat intake recommendation is lower than both the average diet and the 45 percent fat diet fed to mice.
Dr. Christopher Lowry, professor of integrative physiology at CU Boulder, said: ‘It’s extraordinary to think that a high-fat diet alone could change the expression of these genes in the brain.
‘The high-fat group essentially had the molecular signature of a high anxiety state in their brains.’
Although scientists don’t fully understand how a high-fat diet affects anxiety-related behavior, changes in the connection between the gut and the brain are thought to be important.
The brain’s serotonin system is crucial for regulating emotions, including fear. The dorsal raphe nucleus (DR) is the main source of serotonin in the brain, and its serotonin pathways influence various emotional behaviors and thought processes.
When serotonin-producing neurons in specific parts of the DR are activated, they can amplify anxiety-like responses.
The findings, published in the journal Biological researchsuggest that the high-fat diet affected gut microbiome diversity and community composition over the nine weeks of dietary treatment.
The gut microbiome plays a key role in health and disease, including anxiety, both in experimental models and in humans.
Dr. Lowry said: ‘Everyone knows these are not healthy foods, but we tend to think of them strictly in terms of a little bit of weight gain.
“If you understand that they also affect your brain in ways that can promote anxiety, then the stakes become even higher.”
The gut microbiome is dominated by two types of bacteria: Firmicutes and Bacteroidetes. The study results showed an increase in the Firmicutes/Bacteroidetes (F/B) ratio in mice fed a high-fat diet.
A higher ratio of Firmicute to Bacteriodete has been associated with the typical Western diet and higher rates of obesity.
Brisk growth that is faster than that of bacteriodetes leads to less efficient extraction of nutrients from food, leading to weight gain.
A high ratio also plays a role in metabolism and the way food is stored as fat, causing more fat to accumulate in the body.