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Stress, Appetite and a Search for Allostasis

Personal Training

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Any person who works within Health, Fitness and Performance is first an foremost a “stress manager”. It’s our primary role to create situations for clients or athletes to challenge their physical capacities through selectively imposed stress.

As an industry, the aim is to carefully introduce graded exposure to stress through targeted workouts, blocks or phases of training. We can monitor our imposed stress through objective measures such as training load, heart rate feedback and heart rate variability, in addition to other wellness and recovery variables such as the quality and length of our sleep. Our goal as coaches, trainer and clients is to improve stress management through evidence supported training, recovery, sleep and nutritional strategies.

Within our series of posts so far, we have discussed first and foremost what stress is, and how it can be impacted by our movement (1), how we create an environment for clients to thrive (2), as well as how we can target specific domains of performance and the approaches we take within each (3).

In this insight, we’d like to explore the link between stress and nutrition. More specifically, how our capacity to manage stress can impact the nutritional decisions we make consciously and subconsciously.

Many of us may be familiar with the term homeostasis from early stage science, the maintaining of a relatively stable equilibrium. Yet homeostasis assumes that there is an optimal set point at which we look to return to. When we think of this term, it should conjure thoughts of things like body temperature, pH levels, glucose levels and so on. Things that have a very narrow scope for change that don’t dramatically influence the survival rate of the individual.

By definition however, it doesn’t account for the variability we all have within our system.

The term Allostasis however, refers to the changes in energy flow.

This includes our appetite, ingestion, storage of energy within the body, as well as how we mobilise energy for use in activity.

Take blood pressure as an example. Normal blood pressure as we all know, is generally considered to be 120/80. But what we must consider is that is that normal? Or is that simply what’s average?

If we’re a 100m Sprinter or a Powerlifter, our blood pressure will far exceed this during competition. Does this mean we have a blood pressure concern in need of medication? Of course not…

However if our blood pressure becomes chronically elevated due to the training effects and we now reside outside of the “healthy” range for blood pressure, we may now have cause for concern.

Allostasis is a far more fluid concept that considers the variability and fluctuations we all have on a daily basis as individuals.

With regards to nutrition, the impact of stress on allostasis, is bi-directional. Studies have estimated that during stressful periods, approximately 30% of us decrease our eating habits and lose body mass as a result. The remaining 70% of us tend to increase our food intake (stress/binge eating…) during periods in which stress levels are high.

When we consider how our Westernised culture provides such easy access to cheap, high-calorie foods, with little to no effort, it is clear to see why many of us fall in the later catagory.

Re-introduction to the Stress Response

In cases of acute (short-term) stress in the face of threat, whether this be physical or emotional, we see a raft of immediate responses. Heightened awareness, increased heart rate, increase blood pressure and a reduction in blood flow targeted toward providing the muscles, brain and heart with the supply needed in performing life saving activity (fight or flight) all occurs.

As a result, we therefore see a removal of blood flow to non-essentials areas of the body such as the digestive system, for immediate survival during stress situations.

For example, your next meal should be the least of your worries when you’re being chased by a wild animal…

Under short term exposure, the stress response therefore plays an important role within maintaining allostasis and directing energy to where its needed. Impacting, and reducing, our appetite, metabolism and feeding behaviours to optimise our immediate survival.

  • Important to note here is that, if the threat or distress is tied into ones self-perception, i.e. public embarrassment or failure, the response to stress and the subsequent chemical release is even greater.

Impact of Acute Stress on Appetite

Under this premise, our response to immediate stress should typically therefore suppress our appetite, due to the withdrawal of non-essential blood flow.

As mentioned during the introduction, we see this in approximately a third of us, who tend to lose body mass during periods of acutely high stress (work worries, relationship issues or financial difficulty etc.).

How we perceive the threat, our cognitive appraisal of stress, or the value and meaning we place on the threat at hand, influences greatly the severity of our stress response. Certain individuals see no difficulty with public speaking for example, others break down into uncontrollable sobbing at the mere thought.

In response to short-term stress, we therefore see a suppression of appetite to provide blood flow to muscles and organs more vital to immediate survival.

However, what happens when when we can’t calm our stress response and face not short-term, but long-term (chronic) stressors?

The Science behind Stress…

When a stressor is perceived as a threat, causes distress, and is therefore uncontrollable, we see an increase in activity within specific areas of the brain.

Of which, the Hippothalmus-Pituatary-Adrenal (HPA) Axis, is recognised as a fundamental part of our stress response.

* Activation of our HPA axis, results in the release of specific stress response hormones, Cortciotropin Releasing Hormone (CRH), and Adrenocorticotropic Hormone  (ACTH), which bind to the receptors of the adrenal cortex for the release of Glucocorticoids, such as Cortisol, a major stress hormone.

Our chemical response to a stressful event, directly stimulates the release of specific hormones, glucocorticoids, that promote hunger and feeding.

Not only hunger, but hunger directly for sugary, starchy, calorie dense foods…

We would have all experienced post workout, wanting to reach for the very things we know we shouldn’t…

However, our brain has been dealing with hunger for generations however. It has within it, an inbuilt control mechanism to fight this need to feed under stress. The activation of our stress response and subsequent chemical release of CRH, an appetite suppressor, informs the brain to decrease the release of Glucocorticoids, such as Cortisol, that promote an increase in appetite.

A self-balancing response to stress in acute situations.

Yet through repeated firing without recovery, or prolonged exposure of our stress response resulting chronic (long-term) stress, the impact that these hormones have begins to diminish as we decrease sensitivity to their effectiveness.

With the ease of access to these starchy, high-sugar, calorie-dense food we all have, and the decrease in sensitivity towards our hunger control mechanisms, the likelihood that we will become hyperphagic (eating more) when under stressful conditions in the long term surely increases.

As our subsequent digestion of calorie-dense, sugary, starchy food directly influences the primal limbic portion of the brain, including our inbuilt reward system, in an extremely potent way.

This acts as a powerful behavioural reinforcement in times of high stress.

High Stress + Increased Appetite + Access to High Calorie Foods = Danger…

Stress, Body Fat and Diabetes Risk

One of the major risk factors with this type of westernised, high-sugar diet, is the related issues regrading Insulin sensitivity, which has become a hot-topic within the health and fitness industry.

Insulin allows for muscles, fat and the liver to absorb glucose for energy production, as well as playing an important role in fat conversion for energy.

During stress, the release of Glucocorticoids such as Cortisol, interferes with Insulin on multiple levels, disrupting both the release and signalling abilities or the hormone.

Under normal “unstressed” conditions, Insulin and Glucocorticoids have an antagonist effect on our metabolism, one cancelling out the other, enabling a balance within a system constantly responding to its environment.

Under chronic stressful conditions, long term, we see an imbalance within the system.

An significant increase in Glucocorticoids, an example of an imbalanced system without regulation, therefore can be associated with an increase in intake of calorie-dense foods. Simple calorie balance science (calories in vs calories out), tells us that long term accumulation of un-utilised calories results in visceral fat deposition and an increase in measurable body fat.

High Cortisol + High Calorie Foods + High insulin = Increased Body Fat

Yet unhelpfully, this increase in visceral fat further increases the level of intracellular Glucocorticoid,  creating even greater system imbalance and greater fat deposition.

So begins a viscous circle of body fat gain and high stress.

In wide-ranging studies, dysregulation of the HPA axis, our uncontrolled threat response, has been noted as an influencing factor in cases of obesity. This dysregulation decreases the sensitivity for feedback within our systems towards hormones such as Cortisol and Insulin.

Subsequently, tissue sensitivity of both fat and muscles is also reduced reducing the capacity for energy production.

Knowing when to stop…

An important part of satiety, our feeling of fullness, is the signalling of the hormones Leptin and Insulin, both acting as a breaking mechanism to inhibit the feeling of hunger we may have whilst eating.

If we develop resistance to this signalling capacity of Insulin due to repeated stress, becoming desensitised to its effects, the likelihood that we eat for non-metabolic reasons, eating beyond the level of satiety, must surely be considered a contributor to the overweight and obesity epidemic we face in westernised cultures.

This is why our diet and low-level chronic stress lifestyles puts us at such a high risk of  Type II Insulin Resistant Diabetes…

Stress + High Calories + Decreased Insulin Resistance = Reduced Satiety + Further Eating

Restraint Eating and Stress

Restrained Eating: the voluntary controlled effort to restrict calorific intake for bodyweight control.

During periods of high stress, studies have shown that restrained eating tends to lead to an increase in food intake. With the conscious decision to refrain from eating certain palatable foods, we in fact increase our sensitivity to that food source.

Through withdrawal, we have indirectly created a stronger reward-based eating strategy towards this item. Therefore becoming hypersensitive to that food source. Without the ability to calm the craving, we generate a further stress response.

This scenario can easily be visualised, in the all to common, giving up of chocolate.

At a fundamental level, chocolate is a palatable food, high in both sugar and satiation. Capable of generating an opiod release which creates a calming, de-stressing effect by decreasing activation of the HPA, a key component of the uncontrolled stress response described above.

It’s for these reasons that chocolate is so commonly used as a coping mechanism in stressful situations, its calms us.

However each time we stimulate these reward centres of the brain using chocolate as a coping mechanism, we are creating neurobiological adaptions. Quite literally changing the way our brain is wired.

Yet in situations when we restrain our intake of chocolate, it is exactly that which we most crave.

We search unsuccessfully for that same level of satiation and opiod release in other foods, restraining all the while, increasing our sensitivity as a result. In periods of high stress, in combination with restrained eating conditions (heavily reduced kcal diets), where is the first place we tend to go

Emotional Eating and Stress

The use of chocolate, or other highly palatable foods as a coping strategy, also conjures thoughts of emotional eating, the use of food in periods of negative self-focused emotion.

As mentioned previously, if a threat or distress is tied into our personal perception of self, through public embarrassment or perceived failure, the stress response and hormone release is increased greatly.

This increase in response strongly drives that need for sweet, starchy, fatty-type foods.

Re-enter chocolate in a big way.

The chocolate intake increases opiod release as we feel its calming effects, so we reward ourselves further. Soon that single bite turns into a few bars.

This is why it often isn’t as simple as saying “stop eating/drinking “x” and you’ll lose weight…”

We’re dealing with neurobiological factors that are driving us in search for palatable foods to deal with the chronic stress lifestyles and environments we’ve created for ourselves…

Where do we go from here?

Nutritional habits are hard to break. All the willpower in the world may not be enough to change what is a neurological response inbuilt into our systems. As a generation of individuals dealing with chronic, unmanaged, low-level stressors every waking hour of the day, with such ready-made access to the availability for sweet, fatty and high-density calorie foods, we are seemingly caught in a catch-22 situation.

Nutritional strategies play a vital role in the loss of visceral body fat, this is without question. Creating a strategy that finely balances the need for satiation with the knowledge that many of us as humans, have learned to use sugary, fatty, high calorie foods as a coping mechanism, is fundamental to a successful outcome for both client and coach.

Yet least we forget, exercise has the capacity to alter this cycle. By positively influencing the reward centres of the brain and increasing system wide variability through movement and respiration, we develop and increase our capacity to manage stress.

The influence that both the human movement and respiratory systems have at a neurological level in the management of the stress response needs to be a foundational requirement of any training programme when working holistically with a client.

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