My Experience With a 36-Hour Fast as a Person Living With Chronic Illness

My Experience With a 36-Hour Fast as a Person Living With Chronic Illness

Disclaimer

Fasting can place significant stress on the body, especially for individuals with chronic illness, hormonal conditions, nutritional deficiencies, or those taking prescription medications.
This article describes my personal experience only and is NOT medical advice.

Before attempting any extended fast — including a 36-hour fast — please consult a doctor, registered dietitian, or a clinician who understands your health conditions and medications.
Everyone’s body responds differently, and what was tolerable for me could be unsafe for someone else.

Introduction

People with chronic illnesses often search for ways to reduce inflammation, reset their metabolism, or support their body’s natural repair mechanisms. One practice suggested to me was a 36-hour fast, which is believed to help the body enter autophagy, a state linked to cellular repair.

Curious but cautious, I decided to try it — while documenting how my body responded hour by hour, including symptoms, pain changes, and mental clarity. I went into this intentionally, aiming to reduce my medication use temporarily and give my body space to “do its thing.”

This is not a recommendation. It’s simply my first-hand account of a 36-hour fast while managing chronic illness, pain flares, and hormonal changes.

What a 36-Hour Fast Is (and Isn’t)

A 36-hour fast typically means:

  • You finish eating in the evening (ex: 7–10pm)
  • You consume no food until the morning two days later
  • Water, herbal teas, and electrolytes are usually allowed
  • No caloric intake, unless otherwise instructed by a medical professional

Potentially Reported Benefits (Not Guaranteed)

Benefits only of a 36-hour fast include:

1. Enhanced Fat Burning & Ketosis

Between the 24–36 hour mark, the body typically exhausts its remaining glucose stores and shifts to using fat as its primary fuel source. During this transition it produces ketones, which many people experience as a cleaner, more stable form of energy that supports both physical endurance and mental clarity.

2. Potential Activation of Autophagy

Autophagy is the body’s built-in cellular repair and recycling system.

A fast of around 36 hours is long enough to potentially stimulate these pathways, encouraging the breakdown of damaged cells and proteins. While human research is still developing, the biological mechanisms make this response highly plausible.

3. Improved Insulin Sensitivity

Extended fasting naturally reduces:

  • Blood glucose
  • Insulin levels
  • Triglycerides

These changes may improve how effectively the body responds to insulin over time, contributing to better metabolic health.

4. Reduced Inflammation (in some individuals)

Some studies and anecdotal reports suggest that fasting may lower inflammatory markers and oxidative stress. As a result, many people notice reductions in swelling, bloating, or joint discomfort.

5. Enhanced Mental Clarity & Focus

Ketones offer a steady, efficient source of fuel for the brain. During and after a prolonged fast, this often results in:

  • Sharper concentration
  • Fewer energy crashes
  • More stable mood and mental performance

6. Digestive System Rest

A 36-hour fast allows the digestive tract to rest, which can:

  • Reduce bloating
  • Ease IBS-like symptoms
  • Improve bowel regularity once eating resumes

7. Appetite and Craving Reset

Longer fasting periods frequently help reset hunger and satiety signals. Cravings—especially for:

  • Sugary foods
  • Highly processed snacks
  • Mindless grazing tend to diminish. After the fast, hunger hormones often rebalance, making more intentional eating easier.

Particularly for people with chronic illness:

  • dizziness, weakness, nausea
  • low blood pressure
  • electrolyte imbalance
  • difficulty regulating medications
  • worsened pain or flares
  • sleep disturbances
  • hormonal shifts, especially around menstruation
  • potential triggering of migraines or headaches

Again — this varies, and fasting is not suitable for everyone.

My 36-Hour Fast: A Full Breakdown

Before the Fast

I prepared by eating a high-protein, high-fat meal and drinking 500ml of water. I intentionally ate a lot between 8pm and 11pm, with my final meal ending at 10:45pm. The fast would end at 11am two days later.

Hours 0–12

My night began with poor sleep, just under four hours. Upon waking:

  • I took morning medications
  • Continued drinking water
  • Used CBD oil and acupuncture balls to manage early-morning pain
  • Took a light nap mid-morning
  • Had my first hunger wave around 11:30am
  • Drank Matcha tea and water with a little apple cider vinegar

By hour 12, I had consumed about 1 litre of water.

Hours 12–17

This period came with a noticeable shift:

  • Pain levels reduced from severe to moderate
  • Light-headedness began, accompanied by a strange sense of “floating”
  • Hunger arrived in hourly waves, relieved mostly by water
  • Took CBD oil as headaches appeared
  • Noticed increased focus during the dizziness
  • A short 15-minute walk helped
  • Consumed herbal teas and more water (another ~750ml)

Hours 17–24 (Evening Phase)

From 6pm to 11pm:

  • Continued drinking water and a small amount of apple cider vinegar
  • Did some meditation
  • Thirst increased unexpectedly despite high water intake
  • Took night-time medications and 10mg melatonin to ensure sleep
  • Lower back pain worsened, but other pain remained stable
  • Drank sage tea and used my vape, 2 doses

This period was uncomfortable but manageable.

I had been fasting for 30 hours when, at around 4 a.m., I nearly fainted on my way to the bathroom. At that point, I decided it was safer to break the fast with a small omelette and a bit of cheese. What surprised me was not just how I felt during the fast, but how I continued to feel afterward.

Throughout the fast — and even after breaking it — my focus remained unusually sharp, despite running on very little sleep. My energy levels stabilized, and that heightened sense of mental clarity stayed with me well after I’d eaten. At the same time, my appetite had dropped dramatically, which was far from ideal since I’d been working hard to maintain an average intake of around 1,000 calories a day.

This is how my attempted 36-hour fast unfolded, ultimately coming to an end at the 30-hour mark, along with the lingering effects I noticed in the hours that followed.

How My Body Responded

Some effects were difficult, some surprising, and some positive:

Physical Responses

  • Pain regulated, despite 3/4 of a reduction medication consumption and did not flare as badly as expected
  • Significant thirst
  • Intense hunger at first, but reduced later
  • Light-headedness and waves of dizziness, eased by fluids
  • On-and-off headaches
  • Nausea and upset stomach early on, followed by reduced bloating
  • Less-frequent urination despite consuming lots of water & fluids
  • Significant reduction in inflammation

Mental/Emotional Responses

  • Unexpectedly increased focus
  • “Eureka moment” sensations
  • Moments of calm, especially during meditation
  • Less stressed
  • Feeling a bit dazed and euphoric

Medication Adjustments I used only about ¼ of my usual medication, intentionally giving my body room to respond naturally. Surprisingly, discomfort remained tolerable at a 6.5, compared to the morning, where I woke up at a 9.

Hormonal & Chronic Illness Context I unintentionally fasted 3 days before my period, a time that normally triggers a major pain flare. Considering I had an intense flare right before the fast (due to a conference), it was surprising that my pain:

  • Was reduced to around 6.5 without heavy meds
  • Did not escalate
  • Significant reduction in inflammation
  • Was mostly concentrated in the lower back when it did escalate
  • May have been worsened due to a previously broken coccyx injury, as this area consistently triggers the rest

Its important to remember that this is my personal experience, not a universal outcome.

Advice for Others With Chronic Illness Considering a Fast

Again — not medical advice, just supportive guidance for chronic illness communities.

✔️ 1. Talk to a clinician first

Especially if you:

  • take any daily medications
  • have blood sugar instability
  • struggle with low blood pressure
  • have GI conditions
  • are pregnant, breastfeeding, or trying to conceive
  • have a history of disordered eating

✔️ 2. Expect unpredictable outcomes

Chronic illness bodies are not always consistent. What helps one day may flare the next.

✔️ 3. Hydrate intentionally

Plain water alone may not be enough. Many need electrolytes or mineral water to stay stable.

✔️ 4. Be gentle with movement

Short walks helped my dizziness — but overexertion could do the opposite.

✔️ 5. Monitor pain closely

Fasting can either reduce inflammation or worsen pain if the body becomes stressed.

✔️ 6. Do not push through severe symptoms

Signs to stop immediately include:

  • fainting
  • chest pain
  • confusion
  • heart palpitations
  • uncontrollable shaking
  • vomiting

✔️ 7. Honor your hormonal cycle

Fasting near your period may intensify symptoms for people — my experience was unusual and unintentional.

✔️ 8. Break the fast gently

Start with broth, light proteins, or small portions to avoid GI distress.

Conclusion

My 36-hour fast was challenging but unexpectedly clarifying. Despite chronic pain, hormonal timing, and reduced medication use, I experienced regulated inflammation, improved focus, and tolerable discomfort. The dizziness, hunger waves, headaches, and severe lower-back symptoms were difficult, but manageable with hydration, teas, CBD, and rest.

That said, this was my personal journey, influenced by my body, my conditions, and my pain history. No two chronic illness experiences are ever the same, and fasting is not universally beneficial or safe.

If you’re curious about fasting, especially the 36-hour model discussed by experts such as Dr. Mindy Pelz, please do so with medical guidance and a deeply compassionate approach to your body.

Your body is not a machine — it’s a living system deserving of patience, care, and safety.

References & Further Resource Guide:

📄 Key Peer-Reviewed Papers & Reviews on Fasting / IF / Metabolic Health / Autophagy

  • A Narrative Review about Metabolic Pathways, Molecular Mechanisms and Clinical Implications of Intermittent Fasting as Autophagy Promotor Reviews molecular mechanisms by which intermittent fasting (IF) may trigger autophagy — focusing on pathways like AMPK-mTOR, sirtuins, ketone signalling.
  • Effects of Intermittent Fasting on Regulation of Metabolic Homeostasis: A Systematic Review and Meta-Analysis in Health and Metabolic-Related Disorders (2023)    Meta-analysis of multiple human and metabolic-dysfunction studies; examines IF effects on lipid homeostasis, insulin, metabolic parameters.
  • Effects of different types of intermittent fasting on metabolic outcomes: an umbrella review and network meta-analysis (2024)              An umbrella review comparing different IF protocols (time-restricted eating, alternate-day fasting, etc.) vs continuous energy restriction — summarises evidence across many RCTs.
  • The effect of intermittent fasting on insulin resistance, lipid profile, and inflammation on metabolic syndrome: a GRADE assessed systematic review and meta-analysis (2025) Very recent meta-analysis on fasting’s impact on glycemic control, lipid profile, inflammatory markers in metabolic syndrome — relevant to fasting’s systemic effects.
  • The impact of intermittent fasting on body composition and cardiometabolic outcomes in overweight and obese adults: a systematic review and meta-analysis of randomized controlled trials (2025) Reviews RCTs in overweight/obese adults — summarises effects of IF on body composition and cardiometabolic markers.
  • The effects of intermittent fasting on body composition and cardiometabolic health in adults with prediabetes or type 2 diabetes: A systematic review and meta-analysis (2024) Analyses IF effects in prediabetes / type 2 diabetes populations — shows weight, glucose, cholesterol and triglyceride changes.
  • Impact of fasting on the AMPK and PGC-1α axis in rodent and human skeletal muscle: A systematic review (2023) Evaluates whether fasting activates metabolic signalling (AMPK / PGC-1α) in human muscle as seen in animals — finds human evidence limited or inconsistent, underlining important caveats when extrapolating animal data.
  • mTOR-autophagy axis regulation by intermittent fasting promotes skeletal muscle growth and differentiation (2025) Recent article discussing how IF might influence autophagy via mTOR signalling, though much of evidence is still pre-clinical or mechanistic.

 ⛓️‍Links

⚠️ On Autophagy – What the Evidence Does / Doesn’t Show (Despite These Papers)

The molecular-mechanism review (first on the list) explains how IF could trigger autophagy via known pathways (AMPK activation, mTOR inhibition, ketone signalling).

However — as shown by the skeletal muscle review — human evidence is inconsistent: in the case of muscle tissue, fasting doesn’t reliably activate AMPK/PGC-1α under conditions mirrored from animal studies.

Most meta-analyses and RCT-based reviews focus on body composition, metabolic markers (glucose, lipids), inflammation, insulin sensitivity, which are indirect markers — they do not directly measure autophagy (e.g. via tissue biopsy or cellular markers).

Hence — while many papers support metabolic benefits of IF under certain conditions, robust, direct evidence that a 24–48h fast reliably increases “autophagy” in humans remains limited.

🎯 How This Relates to My Personal Account

In my article I described sensations like increased focus, reduced inflammation/pain, dizziness, hunger waves, digestive changes — many of which align with commonly reported effects during longer fasts (e.g. metabolic shift, increased ketone usage, potential cellular “house-cleaning,” and altered energy supply). The literature suggests such changes could be happening under certain conditions, but it’s important to remain aware:

Autophagy is a plausible mechanism if nutrient deprivation is sufficient, but its magnitude and real-world effects in humans remain uncertain.

Fasting-induced benefits (or risks) appear to vary widely between individuals — depending on health status, hydration, medications, sleep, hormonal cycle, and more.

Especially for someone with chronic illness, what works for others (or in animal studies) may not translate directly; this calls for caution and ideally medical guidance.

Disclaimer – Please note, all advice given is based on various healthcare models that have been proven to support patients with sustainability and backed by Public Health England (PHE). Nonetheless, you should run any changes to your routine by your GP as they are your primary carer, it is also important that any other healthcare professionals involved in your care is involved in your goal planning. Don’t forget they hold your medical records and would be familiar with you; this will help everyone to be on the same page and will also enable you to plan more realistically and not overestimate your capacity! 

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