When it comes to looking at stress I encourage you to take a different than you have in the past. Recognize that stress goes far beyond arguments, bills, debt and rush hour traffic.
While those things mentioned above certainly are stressors, I want you to broaden the view of stress and think about it as anything that triggers the stress response in the body.
Stress can be defined as a mental, physical or emotional factor that causes bodily or mental tension, this leaves a lot of room for things in our lives to be considered a stressor.
Hans Selyle, the godfather of understanding stress on a physiological level said “ Stress is not a specific reaction. The Stress response is, by definition, not specific, since it can be produced by virtually any agent.”
Not Black or White
The idea that all stress is bad is completely false, we need certain stressors in our lives to help us adapt and grow stronger from the challenges.
How a person is able to balance their stress burden with their ability to adapt and recover from that stressor impacts whether that will be a positive or negative stressor.
As an example building muscle from going to the gym and lifting heavy weights is a beneficial stress response because you allow the body time to adapt and recover.
Mini challenges to the immune system that allow it to grow stronger and fight off larger infections is a beneficial stressor as well. This is balanced with time after the immune challenge that the immune system recovers.
The forms of stress that are short in duration and allow for you to adapt and recover makes you stronger, but if those same stresses become constant and extreme your body never adapts or recovers and dysfunction is in your future.
We are hardwired to handle infrequent short bouts of intense stress followed by time to rest and recover.
Unfortunately our modern lifestyle is one of chronic low grade stressors that happen all day long with no time to rest or recover.
Life requires the body to constantly be checking and establishing equilibrium.This equilibrium is known as homeostasis, and what brings us back to homeostasis are adaptations.
For the purpose of this blog we are going to apply this to the processes of gaining body fat, and how constant stressors impacts health.
Our stress response is a flow of adaptive changes that start in the central nervous system that cause mental, behavioral and physical changes.
Let’s say we encounter a bear while out on a hike. In response to the threat of a bear attack the adrenal glands releases the stress hormones adrenaline (epinephrine and norepinephrine) and cortisol.
These stress hormones cause the heart beat faster, increase the pulse and move blood to the extremities.
The secretion of cortisol also triggers the body to mobilize more glucose and fat from fat cells into the blood to be used as fuel to fight or run away.
The bear sees you and runs away, but you can still feel the physical effects of the stress hormones.
When you have a stressful event but don’t fight or run away from the situation your body doesn’t metabolize the stress hormone cortisol.
Adrenaline runs it course and is cycled out of the system in a short amount of time.
Cortisol on the other hand sticks around for much longer and signals the body to refuel after the stressful event.
In everyday life we are far more likely to have unpaid bills, be late to work , sit in traffic or have an argument than run into a bear unexpectedly.
Adrenaline and cortisol are released to cope with any stressor, the type of stress doesn’t matter your body responds the same way.
Your stressed out lifestyle is the same as encountering an unexpected bear, but all day long. With this volume of stress your body can’t recover and repair from the bouts of stress leading to negative adaptations taking place.
Stress And Muscle Loss
When a stressful event happens the body switches from an anabolic phase of building to a catabolic phase of breaking down.
Fats are mobilized and dumped into the system and the liver goes into overdrive to produce any glucose available in the body.
Due to chronic stress the body will break down muscle tissue into amino acids that will be shuttled to the liver with fats to produce glucose to fuel the stress response.
Keep in mind the more muscle mass you have on your body the higher your metabolic rate and need for calories will be.
By breaking down hard earned muscle to fuel chronic stresses your metabolic rate will be lowered meaning you will burn fewer calories on a daily basis, even at rest!
Stressful situations tell the body to quit diverting energy to storage, and start mobilizing resources. As a result your cells responsiveness to the storage hormone insulin is turned off.
Short infrequent bouts of this stress response don’t create problems, but the constant stress response leads to a more insulin resistant state that long term creates problems.
When your cells no longer respond the to storage hormone insulin, the body will release more insulin in an attempt to clear glucose from the blood stream. Too high of blood glucose for too long is toxic.
With high levels of insulin circulating, burning body fat is nearly impossible. Not to mention because your cells aren’t responding to insulin they aren’t getting the glucose they need.
This means that even if someone is eating in a caloric deficit in an attempt to lose fat they will lose much less fat while in this deficit.
In addition when the person returns to eating more maintenance calories that don’t put them in a deficit, those extra calories will be stored more easily as body fat.
Adrenals, Thyroid and Leptin
The thyroid is a very complicated, and important gland in the body that controls our metabolic rate and in turn digestion, body temperature and pulse.
Your metabolic rate determines your caloric needs each day, but it is not set and can be boosted or decreased depending on a number of factors including diet, sleep, exercise and stress!
The thyroid is supported by the adrenal glands, if the adrenals are overburdened by too much stress for long enough it will impair thyroid function.
Leptin is a hormone secreted from your fat cells, letting the brain know how much stored energy we have. Leptin also signals satiety to the brain to squelch hunger.
Leptin helps to increase or decrease our metabolic rate by delivering a report on how much energy we have available to the brain which communicates with the thyroid to adjust the metabolic rate.
Too much cortisol from stress reduces the conversion of the inactive form of thyroid hormone T4 to the active and usable form T3. We require the active thyroid hormone T3 to regulate the metabolism.
The thyroid will increase or decrease the metabolism based on the amount of leptin, and stress hormones circulating.
You can think of stress and your metabolism somewhat like a teeter totter. When stress is raised for a long period of time the metabolism will be lowered. When the metabolism is functioning at a higher rate the body is in less of stressed state.
I would like to note that cortisol isn’t bad, we require cortisol to handle stress and it helps us to wake up and be alert in the morning.
Too much cortisol though does cause dysfunction in the body and that is what happens with chronic stress.
Constantly elevated levels of cortisol are a quick path to a slower metabolic rate resulting in less calories being burned and gaining body fat.
Cortisol will cause the breakdown of muscle to provide amino acids that will be converted to glucose. Less muscle tissue results in a lowered metabolic rate and less calories being burned.
Protein synthesis (muscle building) will also be down regulated to make sure the body has enough amino acids to convert to glucose and fuel stressful events.
Cortisol causes cells to become insulin resistant, making it much more difficult to lose fat even in a caloric deficit and more likely to gain fat when you return to maintenance calories.
The elevated insulin blocks the communication between the hormone leptin which lets the brain know how much energy we have in storage.
This body fat report is then sent to the thyroid to adjust the metabolic rate based on the report from leptin and the brain.
Lastly high levels of cortisol interfere with the conversion of the inactive thyroid hormone T4 into the active T3 that helps to regulate metabolism.
As you can see here there are a number of ways that stress can not only lower the metabolism and cause someone to gain fat.
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