Every time you’re confronted with a stressor — whether it is a traffic jam, a fire, or a bounced check — your body releases a cascade of stress hormones such as epinephrine, adrenaline, and cortisol. They, in turn, send a volley of signals to various parts of your body to ready them for action.
For instance, your liver releases glucose to provide instant energy to muscle cells. Your lungs expand, your heart beats faster, and your blood pressure rises to send more oxygen-rich blood throughout your body. Your bowel and intestinal muscles contract. And so on. All of which can lead to common stress-related conditions ranging from chronic hypertension, angina and gastric reflux, to constipation and irritable bowel syndrome, to depression, anxiety, and fatigue.
Stress can even make you fat. Cortisol is not only a powerful appetite trigger, but chronically high levels of cortisol actually stimulate the fat cells inside the abdomen to fill with more fat, creating a life-threatening form of fat called visceral fat, which puts you at higher risk for heart disease and diabetes.
Stress also inflicts its damage in more insidious ways by affecting the very system that is supposed to guard your health: your immune system. Turns out that, like most systems in the body, the immune system has a feedback loop. After it finishes attacking foreign invaders with inflammatory chemicals, the brain sends out cortisol, the stress hormone, to shut down this inflammatory response and send the immune system back into a quiet, or homeostatic, state. But if your body is releasing cortisol all the time — as it does under chronic stress, such as commuting — then your immune system is constantly being suppressed, increasing your risk of illness.