The Physiology of
Stress and How to Manage It
Provided
by American
Council on Exercise
You’ve likely
experienced the physiological effects of stress—sweaty palms, racing
heart, shallow breathing—and are familiar with the feeling of being overwhelmed
it can bring. The stress response is part of the “fight or flight” mechanism
that has helped our species thrive. However, the demands of modern life make
this adaptive response problematic for our long-term well-being.
This
article covers the physiological underpinnings of stress, its impact
on various bodily systems and useful strategies for navigating it.
The Physiology of
Stress
Stress can be defined
as a state of disharmony or altered homeostasis within
an organism. In other words, we strive to live in a stable and
balanced environment, but stressful events alter homeostasis and
upset the harmony of the body's systems. The
body’s stress response is governed by the sympathetic nervous system. When
faced with acute danger, your body responds with a cascade of physical and hormonal changes that prepare you
to respond. Some of these changes include:
·
Increased blood
pressure and heart rate
·
A surge of stress hormones (epinephrine, norepinephrine and
cortisol)
·
Reduced blood flow
to internal organs and increased blood flow to muscles
·
Heightened muscle
tension
·
Inhibition of
immunity, digestion and reproductive functions
When confronting
danger, these physiological responses play a protective role in
promoting survival. Once activated, the stress
response mobilizes the body’s available resources to meet the
demands of a dangerous or stressful situation. Any bodily functions
and processes not immediately necessary, such as
growth, digestion and the maintenance of hormones responsible
for reproduction, get downregulated. Unfortunately, when the perceived
threat stems from constant daily pressures, these responses
can impact your overall well-being. Eventually, the body’s stress response may wreak more havoc
than the stressor itself, impacting numerous health
outcomes.
Chronic Stress
and Body Weight
For some people,
chronic stress may be associated with higher body weight. A variety of
factors underlie this relationship. While some of the hormones associated with
the stress response inhibit hunger, others increase it. Cortisol typically
spikes in the latter parts of the stress response and stays elevated during the
recovery phase. This hormone increases hunger and motivation to eat as a means
of replenishing calories that might have been lost while responding to a
stressor. The body’s stress response stimulates the sensitivity of the
reward system leading to cravings for
hyperpalatable comfort foods, such as quick-digesting carbohydrates
and those that are high in fat, and people may begin
to eat for emotional reasons rather than nutritional ones.
In addition, cortisol
spurs an increase in fat storage, particularly around the midsection. The fat
cells located in the abdomen, known as visceral fat, are particularly
sensitive to cortisol and store more fat than other areas when exposed to it.
Chronic Stress and
Digestive Function
Digestion is rapidly
inhibited during stress. Blood flow is diverted away from digestive organs,
gastrointestinal enzymes responsible for breaking down food decrease, and
peristalsis (the muscular contractions of the intestines that help move food
along) is inhibited. When facing a critical threat, this is beneficial.
Digestion is not immediately necessary and blood flow is
redistributed to other working tissues, such as the muscles needed
for fight or flight. When stress becomes chronic, however,
this alters the flow of the digestive system and it no
longer functions efficiently. Stress can also increase markers of gastrointestinal inflammation and is related to
conditions such as irritable bowel syndrome, ulcers,
Crohn’s disease and ulcerative colitis.
Chronic Stress and
Mental Health
Chronic stress can
negatively impact mood, and high levels of stress are
related to increased rates of both depression and anxiety.
Prolonged exposure to cortisol and other corticosteroids can increase feelings
of anxiety and contribute to the development of depression. Elevated cortisol
levels are often seen in individuals with major depression, and animals with
high corticosteroid levels show symptoms of depression,
such as poor sleep, locomotor changes, reduced appetite and low
libido. Additionally, individuals exposed to early-life stress are more likely to
experience clinically significant mental health outcomes in adulthood.
Chronic Stress and
Disease
Inflammation is part of
the immune response to illness or injury, where white blood cells, antibodies
and cytokines defend compromised tissues. Like stress, this is beneficial in
the short term.
Chronic inflammation, however, promotes the development of most chronic
diseases. Unchecked stress can incite or perpetuate systemic inflammation, and
research reveals that stress is a common risk factor in
75 to 90% of modern diseases, including cardiovascular disease,
diabetes, liver disease, Alzheimer’s disease and
cancer.
The Benefits of Stress
While it may seem that
stress is inherently negative, it can be beneficial. Stress can boost
cognition, motivation, memory, creativity, vigilance and
perseverance. Furthermore, the way we perceive a stressor has a significant
impact on how it affects us. Simply viewing a stressor as a “challenge” rather
than a “threat” yields better physical and psychological consequences. Stress
mindsets (our attitudes and beliefs about the effects of stress) alter our
behavioral and psychological responses to threats, and thus, our long-term
outcomes. For
example, a study examining the association of perceived stress and
depression in
college students found that the higher the level of
stress perception the more likely the person is to experience
depression.
To objectively test the
effect of mindset on
the physiological stress response, researchers set up an experiment involving a
mock interview and measured two stress hormones: cortisol and
dehydroepiandrosterone (DHEA). As mentioned earlier, cortisol is behind some of
the deleterious effects of chronic stress. It helps break down stored
fuel and inhibit unnecessary systems during the stress response, but
chronically high levels can hamper health. DHEA also rises during
a stress response, and promotes
brain growth and recovery and affects emotions, immune
reactions, mood and behavior because it easily crosses the
brain-blood barrier. Researchers randomly assigned participants to watch
either a “stress is enhancing” or “stress is debilitating” video before their
mock interviews. They found that, compared to the “stress is debilitating”
group, those who watched the “stress is enhancing” video had a dramatically
greater rise in DHEA, which is linked to improved health
outcomes in response to stress.
Stress is a natural
part of life. When unchecked, the body’s physiological response can
negatively impact health. However, your mindset can transform your
stress response, allowing it to enhance creativity, motivation and
perseverance, ultimately helping you become more resilient in the
face of future stressors.
AUTHOR
Kelsey Graham
Kelsey Graham, MEd, CHES, is an Assistant
Professor and Director of the Health and Wellness Coaching and Personal
Trainer Certification Programs at San
Diego Mesa College. She has more than 10 years
of experience in the fitness industry, working as a personal trainer, group
fitness instructor and health coach. Her love of movement lies in its ability
to go beyond physical health and improve mental and emotional well-being.