After a stressful day of work, good intentions concerning dieting and exercise can quickly go out the window. Now, a new study from researchers at the University of Zürich in Switzerland has demonstrated how stress can influence regions of the brain involved with self-control.
Their findings, published in Neuron, shed further light on how stress and self-control interact in the human brain, with the effects of stress operating through multiple neural pathways, according to lead author Silvia Maier, a PhD candidate in neuroeconomics.
“Self-control abilities are sensitive to perturbations at several points within this network,” she explains, “and optimal self-control requires a precise balance of input from multiple brain regions rather than a simple on/off switch.”
Important decisions have to be made in stressful conditions on a daily basis. Sometimes, stressful circumstances can compromise an individual’s ability to exhibit self-control, in turn affecting the decision-making process.
Despite how frequently such decisions are made, however, the manner in which stress affects processes within the brain is not fully understood.
To investigate, the researchers assessed a number of individuals who were attempting to maintain a healthy lifestyle in terms of diet and exercise and looked at how stress affected choices they made about food.
A total of 29 participants were observed and evaluated by an experimenter while one of their hands was immersed in cold water for 3 minutes in order to induce a moderate level of stress.
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Following this treatment, the participants had to choose repeatedly between two food options presented on a screen – a tasty but unhealthy option and a healthy but less tasty option – for them to eat following the experiment. Maier told Medical News Today that the food options on offer were tailored to each participant.
“As what each person will find tasty is very unique, we try to cater to everyone’s taste by asking for participant’s taste ratings on a large set of foods beforehand,” she explained. “We then customized a set of foods for each participant in the experiment that covered a wide spectrum of taste and health trade-offs.”
To prevent preferences unrelated to taste influencing the decisions of the participants, Maier told MNT that they also excluded any individuals with food intolerances or allergies from participation in the study.
These participants’ decisions were then compared with those made by a further 22 participants who did not undergo the stress-inducing treatment. In addition to assessing the choice made by the participants, the researchers also conducted fMRI (functional magnetic resonance imaging) scans to see how their brains were affected.
The researchers found that the participants subjected to stress-inducing treatment were more likely to value a food’s taste over its healthfulness when choosing what to eat compared with participants who were not stressed. This finding indicated that stress increased the influence of immediately rewarding attributes on choice and reduced self-control.
In the brains of the participants subjected to stress, changes were observed in various regions of the brain. The researchers noted increased connectivity between the ventromedial prefrontal cortex (vmPFC) region and the amygdala and striatal regions – regions associated with perceiving tastiness.
Reduced connectivity was also observed between the vmPFC region and the dorsolateral prefrontal cortex regions – regions associated with successfully exhibiting self-control. However, only some of these connectivity changes were associated with cortisol, a hormone associated with stress.
Senior author Todd Hare, an assistant professor in neuroeconomics, states that these findings indicate self-control can be inhibited by even moderate levels of stress, which is important as moderate levels of stress affect a larger portion of the population than extreme stress events. He adds:
“One interesting avenue for future research will be to determine whether some of the factors shown to protect against structural brain changes following severe stress – such as exercise and social support – can also buffer the effects of moderate stress on decision making.”