Stress physiology: Why pushing harder can make you feel worse. January Reset theme

By Dr Michael Barnish, Strategic Advisor of Life Sciences at REVIV Global

Many high functioning people respond to feeling “off” by adding more pressure, more training, more restriction, more productivity. Physiologically, this can backfire. When stress systems stay switched on for too long, the body shifts away from restoration and towards short term survival priorities. This can show up as lighter sleep, gut symptoms, appetite changes, low mood, higher anxiety, and slower recovery.

Chronic elevation of the stress response can disrupt sleep architecture, digestion, appetite regulation, and tissue repair, so “more effort” can worsen the very symptoms you are trying to fix. [1,2]

1. The stress response is built for short bursts, not constant load

Stress is not inherently bad. Acute stress helps you respond to challenge through coordinated activation of the sympathetic nervous system and stress hormone pathways. Problems arise when the “on switch” is repeatedly triggered without enough recovery time, creating cumulative physiological strain, often described as allostatic load or allostatic overload. Over time, this increases multi system wear and tear and can amplify symptom sensitivity. [1,2]

2. Sleep and stress amplify each other

Sleep loss is itself a biological stressor. Experimental sleep deprivation is associated with increased stress system activity, and stress, in turn, disrupts sleep regulation. This is a self-reinforcing loop, poor sleep increases stress reactivity the next day, which then further impairs sleep the following night. [3]
Even modest sleep restriction can affect metabolic regulation, including reduced insulin sensitivity, increased hunger ratings, and increased energy intake in controlled trials. When you feel stressed and tired, the brain also tends to respond more strongly to food cues and reward signals, making cravings and impulsive choices more likely. [4]

3. Digestion changes under stress, because the gut is part of the stress network

The gut is tightly connected to the brain through neural, immune, endocrine, and microbial pathways. Stress can influence gut motility, barrier function, immune signalling, and microbiota composition, and these gut changes can feed back into mood, energy, and cognitive function. For some people this looks like bloating, nausea, reflux, altered bowel habits, or abdominal discomfort, especially during high pressure periods. [5]

4. Chronic stress shifts the autonomic balance, and you can often see it in heart rate variability

When sympathetic tone is persistently elevated, parasympathetic activity tends to drop. Heart rate variability, an index of autonomic regulation, is commonly reduced during psychological stress across many paradigms, reflecting reduced vagal modulation and a system that is less flexible. [6] Lower flexibility often feels like, “I cannot switch off”.

5. More training, when recovery capacity is already low, increases total load

Physical training is a stressor, even when it is beneficial. When training load plus life stress exceeds recovery capacity, performance and wellbeing can deteriorate. In more severe cases this can resemble non-functional overreaching or overtraining syndrome, with fatigue, sleep disruption, mood change, and persistent under performance. A recent scoping review highlights how multi system this can be, and why a single biomarker rarely explains it. [7]
 

A. Use the breath

Slow breathing with a longer exhale is a simple way to bias the autonomic nervous system towards parasympathetic activity. Reviews show slow breathing is associated with improved autonomic markers and emotional regulation in many studies. [8,9] A randomised controlled trial also found brief daily breathwork improved mood and reduced physiological arousal, with exhale focused breathing showing particularly strong effects. [10]

Try this now

• 3 minutes, inhale 4 seconds, exhale 6 to 8 seconds
• Keep the exhale smooth, do not force air out
• If you feel lightheaded, return to normal breathing

B. Pair stress tools with the fundamentals

• Morning daylight exposure, consistent wake time and a realistic evening wind down, to protect sleep regulation. [11]
• Regular meals with adequate protein and fibre, to reduce hunger spikes and decision fatigue, especially after short sleep. [4]
• Training plan that includes easy days and lighter weeks. Adaptation happens during recovery, not during load. [7]
• Caffeine timing, ideally earlier in the day, if sleep is fragile and genetics are not known. [12,13]

C. When to seek professional support

If anxiety, low mood, insomnia, panic symptoms, disordered eating behaviours, or persistent physical symptoms are present, get support early. This is a health issue, not a willpower issue. A clinician can also screen for contributors like thyroid disease, iron deficiency, medication effects, sleep apnoea, or gastrointestinal pathology.
 

1. Goldstein DS. Stress and the extended autonomic system. Auton Neurosci. 2021 Dec;236:102889. PMID: 34656967.
2. Guidi J, Lucente M, Sonino N, Fava GA. Allostatic load and its impact on health: a systematic review. Psychother Psychosom. 2021;90(1):11 to 27. PMID: 32799204.
3. Nollet M, Wisden W, Franks NP. Sleep deprivation and stress: a reciprocal relationship. Interface Focus. 2020 Jun 6;10(3):20190092. PMID: 32382403.
4. Zhu B, Shi C, Park CG, Zhao X, Reutrakul S. Effects of sleep restriction on metabolism related parameters in healthy adults: a comprehensive review and meta analysis of randomised controlled trials. Sleep Med Rev. 2019 Jun;45:18 to 30. PMID: 30870662.
5. Cryan JF, O’Riordan KJ, Cowan CSM, Sandhu KV, Bastiaanssen TFS, Boehme M, et al. The microbiota gut brain axis. Physiol Rev. 2019 Oct 1;99(4):1877 to 2013. PMID: 31460832.
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7. Carrard J, Rigort AC, Appenzeller Herzog C, Colledge F, Königstein K, Hinrichs T, et al. Diagnosing overtraining syndrome: a scoping review. Sports Health. 2022 Sep to Oct;14(5):665 to 673. PMID: 34496702.
8. Zaccaro A, Piarulli A, Laurino M, Garbella E, Menicucci D, Neri B, et al. How breath control can change your life: a systematic review on psychophysiological correlates of slow breathing. Front Hum Neurosci. 2018 Sep 7;12:353. PMID: 30245619.
9. Bentley TGK, D’Andrea Penna G, Rakic M, Arce N, LaFaille M, Berman R, et al. Breathing practices for stress and anxiety reduction: conceptual framework of implementation guidelines based on a systematic review of the published literature. Brain Sci. 2023 Nov 21;13(12):1612. PMID: 38137060.
10. Balban MY, Neri E, Kogon MM, Weed L, Nouriani B, Jo B, et al. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Rep Med. 2023 Jan 17;4(1):100895. PMID: 36630953.
11. He M, Ru T, Li S, Li Y, Zhou G. Shine light on sleep: morning bright light improves nocturnal sleep and next morning alertness among college students. J Sleep Res. 2023 Apr;32(2):e13724. PMID: 36058557.
12. Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, et al. The effect of caffeine on subsequent sleep: a systematic review and meta analysis. Sleep Med Rev. 2023 Jun;69:101764. PMID: 36870101.
13. Low JJL, Tan BJW, Yi LX, Zhou ZD, Tan EK. Genetic susceptibility to caffeine intake and metabolism: a systematic review. J Transl Med. 2024 Oct 22;22(1):961. PMID: 39438936.