Stress and food are two irrefutable parts of our lives. Food is our fuel and stress can occur as a result of anything from work to relationship troubles to simply deciding what to wear. Physical exercise, emotional triggers, and even thinking can be stress-inducing. Often, we will imagine stressful situations or ruminate over unsettling experiences. Regardless of its source, stress is interconnected with the way we eat. We are often told that food and stress are intertwined, but it is not always so clear how.


Fight or Flight Vs. Rest and Digest: The Autonomic Nervous System, Stress, and Food

At a physiological level, stress and food activate different branches of our autonomic nervous system (ANS). Food in your stomach is one activator of the parasympathetic nervous system, while stress activates the sympathetic nervous system. The ANS, which both these systems are a part of, regulates our bodies’ unconscious processes. These include breathing, digestion, blood flow – all of those things that happen without us having to think about them.


The branches in the ANS have to stage a major balancing act. One branch, the sympathetic nervous system (SNS), is responsible for our fight, flight, and freeze responses. In the face of a threat, the SNS mobilizes the body to take action. The parasympathetic nervous system (PSNS) is the biological opposite; it is responsible for returning your body to its resting state after a threat is perceived as passed.


The PSNS is commonly known as the rest and digest system because it is responsible for healing and plays a role in digestion. The SNS usually triggers a response and the PSNS inhibits it. This interaction is commonly referred to as fight or flight vs. rest and digest. Both systems have functions that are extremely important for our health and well-being, so it is critical to fuel a balance. Often, this may seem easier said than done.


Where Does Food Come In?

Stress triggers our primal reactions: fight or flight. When we perceive or experience stress, the SNS activates glands and organs that are necessary for fighting or fleeing. It produces stress hormones, such as adrenaline, that foster that rush you feel in stressful situations. You know the increased heart rate and blood pressure you associate with an adrenaline rush? Those symptoms are a result of your blood localizing in your muscles and action centers of your brain.


That energy surge is essential for fight or flight, and in threatening situations, it allows you to respond with the necessary urgency. However, when that nervousness and panic is not channeled into a threat response, it sits with you. This can lead to the collapse or freeze response. Fight or flight responses may also be known as fight, flight, or freeze due to the relationship.


The fight or flight instincts of the SNS are not just activated by threat. Coming face to face with a black bear could elicit the same physiological response as one too many Red Bulls. Sugar, caffeine, cigarettes, and alcohol or drugs in excess can produce the same chemical response. Thoughts can also be powerful triggers of the SNS.


Fight or flight is activated by perception of threat. For some individuals, social situations, schoolwork, food, and a wide range of other scenarios are extremely stressful. It may be circumstantial, but these perceived threats elicit the same caliber response as a life or death situation necessitating fight or flight. Again, blood flow to your muscles and brain increases. Simultaneously, blood flow for digestion decreases. Thus, you have stress hormones coursing through you without a fight or flight reaction to serve as an outlet to run them off. This may feed into a collapse or freeze response and can lead to agitation, panic, and bad mood.


The SNS is normally dominant during the day. It keeps us alert and ready to act. It is important to maintain balance because SNS activity breaks down your body if it is dominant for too long. When the SNS is in charge, your energy is diverted from healing, building tissue, and eliminating waste.


The SNS relies on energy from your glands rather than food. This can feel great at first, adrenaline and endorphins may flow, but it is usually followed by fatigue or crash. SNS activity also shuts down digestion, which can give way to a depressed state or freeze. PSNS activity is necessary to help your body find its resting state again and rejuvenate.


In theory, this sounds easy enough. Ideally, there would be an on and off switch for your SNS and PSNS and we could shift between the two with ease. Fight or flight vs. rest and digest would just be a choice. Unfortunately, that is not quite the case. When survival, stress hormones are running, PSNS rest, digestion, and healing cannot occur. Furthermore, the PSNS takes longer to be activated.


Food in your stomach is one mode of PSNS activation. Have you ever noticed yourself getting sleepy after a big meal? That is your PSNS hard at work.


Food can be one source of fuel for your PSNS. However, fight, flight, or freeze responses, depression, and anxiety may impact appetite, so it is not always a perfect option. It is simply one tool for maintaining your “window of tolerance,” which is the state of being when we function optimally.


What Does Healthy Stress Look Like: Your Window of Tolerance

Dr. Laura K Kerr, Ph.D. created a guide to your window of tolerance. This window refers to your tolerance of arousal. One primary source of arousal is stress.


When there is too much arousal, you are in the hyperarousal zone. This zone is where your SNS fight or flight responses are activated. Shaking, impulsivity, anger, and emotional reactivity are signs that you might be in the hyperarousal zone.


The other extreme is the hypoarousal zone. When your PSNS is active and there is too little arousal, you are likely in this zone. When extreme, passivity, reduced movement, emotional numbing, the inability to say no, and a lack of energy may be signs that you are in the hypoarousal zone.


Fight or flight vs. rest and digest may be comparable to hyperarousal and hypoarousal. However, it is not so dichotomous. These zones exist on a continuum. The midpoint is the optimal arousal zone, or the “window of tolerance.” In this zone, you may be thinking and feeling simultaneously, experiencing empathy, and reacting appropriately to the situation at hand.


We shift along the arousal continuum constantly. Food can help us shift from hyperarousal back to our window of tolerance. Mindfulness practices such as centering, breathing, grounding, alignment, and walking exercises also help to be in the present moment and get back to your optimal arousal zone.


Food and stress greatly impact our ANS. Hyperarousal and hypoarousal zone symptoms can be physical indicators of how. We are bound to shift along the continuum, but too much time in either extreme can break down your body and your mindset. It is crucial to understand your ANS and the roles stress and food play in your SNS and PSNS activity. When you are in tune with your body and those processes, you can hone strategies that utilize food, mindfulness, or alternate practices to stay within your window of tolerance and function optimally!


Some Resources for Managing Fight or Flight Vs. Rest and Digest: Staying Within Your Window of Tolerance

Breathing is a remarkable tool for regulating yourself and your stress levels. It can help bring you back to your window of tolerance in moments of heightened stress. Read more about how breathing can ease anxiety and stress here.


Another part of regulating stress is self-care. There are infinite ways to show yourself love and support yourself through stressful periods. Most of them you can do at home with things you already own! Review our at-home self-care kit here to learn more.

Thank you to Laura Riss, clinical psychologist, and Mia, Best Within You Therapy & Wellness intern, for this blog post.


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