Beyond concerns about your waistline, eating fatty foods during times of stress can actually harm our body's ability to recover and can lead to reduced oxygen supply to the brain and poor blood vessel function. In two new studies, researchers from the University of Birmingham found that eating high-fat meals during times of stress reduced brain oxygen supply to the prefrontal cortex, leading to a depletion of oxygen delivery (a 39% reduction in oxygenated hemoglobin) compared with eating low-fat meals.
Rosalind Baynham, from the University of Birmingham, said: "When we are stressed, different things happen in the body: our heart rate and blood pressure rise, blood vessels dilate, and blood flow to the brain increases. We also know that the elasticity of blood vessels - a measure of blood vessel function - decreases after mental stress. We found that eating high-fat foods during mental stress reduced blood vessel function (measured by brachial artery flow-mediated dilation, or FMD) by 1.74%."
This reduction in vascular function lasted up to 90 minutes after the stress was relieved. The good news, however, is that eating foods high in polyphenols, such as cocoa, berries, grapes, apples and other fruits and vegetables, has no impact on blood vessel function.
To evaluate their findings in human trials, the researchers recruited young, healthy adults and had them each eat two buttery croissants for breakfast.
"We then had them do mental arithmetic at increasing speeds for eight minutes, and were reminded when they answered incorrectly," Benham said. "They could also see themselves on the screen while doing the exercises. The experiment was designed to simulate the everyday stressors we might face at work or at home."
She added: "Previous research has shown that for every 1% decrease in blood vessel function, there is a 13% increase in cardiovascular disease risk. Importantly, our study shows that this impairment in blood vessel function lasted longer when our participants ate croissants."
The good news? Choosing low-fat foods and drinks will still have an adverse effect on blood vessel function (a 1.18% reduction), but the body will return to normal quickly after the stress subsides.
Jet Veldhuijzen van Zanten, professor of biological psychology at the University of Birmingham, said: "It was surprising that there was such a significant difference in how well people recovered from stress when they ate high-fat foods. The effects were likely to be more severe for people who were already at increased risk of cardiovascular disease."
So reaching for high-fat snacks in response to stress at work or in life may actually be more harmful to your health than previously thought, researchers warn.
"We all face stress on a regular basis, but especially for those who work high-stress jobs and are at risk for cardiovascular disease, these findings should be taken seriously," Zanten said. "This research can help us make decisions to reduce our risk rather than make it worse." "
However, that's not all. Reduced oxygenation can lead to bad moods or other mental health issues, which can make stress worse and worsen health problems.
Catarina Rendeiro, professor of nutritional sciences at the University of Birmingham, said: "We know that when people are stressed out, they tend to gravitate toward fatty foods because it's a more convenient option if they're short on time, or as a reward for coping with stress. But by doing so, they can make their physical and psychological responses to stress worse. "
Eating low-fat foods can both relieve stress and lessen the impact on your physiology.
"The world today is extremely stressful, and even without external factors such as war or a cost-of-living crisis, stress is something we all need to face," Benham said. "So the next time you're at a big meeting or job interview, try turning down the free cookies and eating berries instead. You might find yourself feeling more relaxed and better able to handle stress.
The research was published in the journals Frontiers in Nutrition and Nutrients.