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
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
Despite how frequently such decisions are made, however, the
manner in which stress affects processes within the brain is not fully
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
Stressed participants more likely to choose tasty, unhealthy
food over healthy options.
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.
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
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
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."
Recently, MNT reported on a study suggesting that alterations
to gut bacteria induced by stress in early life could contribute to
the development of anxiety
Source: Medical News Daily