How Stress Affects Your Health
Anyone who has experienced chronic stress would be able to tell you that it isn't great for your health or well-being in the long run. However, stress is probably having a greater impact on your day-to-day body function and coming from more sources than you realize.
First, let's look at how your body responds to stress using the HPA (hypothalamic-pituitary-adrenal) axis. This system works great for short-term stress and is essential for keeping us alive. If a lion came around the corner on one of our early ancestors, they needed to be able to get away FAST or we wouldn't be here.
When a stressor happens, the hypothalamus (in your brain) releases corticotropin releasing hormone (CRH). This CRH acts on the pituitary gland (also in your brain) and tells it to release adrenocorticotropic hormone (ACTH). ACTH travels in the bloodstream to the adrenal glands, which sit on top of your kidneys. When the adrenal glands sense the ACTH, they release cortisol.
Cortisol has a number of effects. It increases blood glucose to provide energy needed to deal with the stress (i.e: lion, burning building, etc). It also causes the release of epinephrine (adrenaline) and norepinephrine, which act to increase heart rate and redirect blood flow toward skeletal muscle and away from less critical systems like the digestive system.
The cortisol released by the HPA axis in response to stress also has an impact on other systems. You also have a hypothalmaic-pituitary-thyroid (HPT) axis and cortisol inhibits both the production of TSH and the conversion of T4 (inactive thyroid hormone) to T3 (active thyroid hormone) by the HPT axis. When this is constant, it can really throw off your thyroid hormone levels and cause all kinds of other issues.
Ladies, you also have a hypothalamic-pituitary-gonadal (HPG) axis that regulates your cycle. In very simple terms, cortisol from the HPA axis affects numerous female hormones that regulate your cycle and can create imbalances that cause things like PMS, heavy or painful periods, etc.
Again, the system is pretty useful for responding to short-term stress but can create a lot of issues when the stress is ongoing.
So, now that we know how the body responds to stress, what exactly triggers this response? Stress can be more "obvious" things like a car wreck, loss of a loved one, taking care of kids, managing debt, a work deadline, running late, or losing your credit card.
What you may not know is that exercising too much, inadequate intake of total energy (calories) or macronutrients (carbs, fats, protein), closely monitoring your food intake, poor body image, and inadequate sleep all activate the stress response as well.
Chronic stress not only impacts hormones like mentioned above, but it also increases insulin levels (which can lead to diabetes), increases intestinal permeability (which can lead to food intolerance), and changes your gut microbiome (which can create various GI side effects).
This is just a very surface level overview of the stress response and what causes it but hopefully it gives you an idea of not only how many conditions might be rooted in stress, but how important stress management is to overall health.