Fasting and Mental Health: How 4-21 Day Fasting Periods Transform Mood and Well-being

If you’ve been struggling with persistent mood issues, chronic fatigue, or that sense that conventional treatments aren’t quite reaching the root of your problems, you’re not alone. What if I told you that some of the most compelling research on mental health improvement doesn’t come from a new medication, but from an ancient practice backed by rigorous modern science?

A groundbreaking study published in PLOS ONE followed 1,422 people through medically supervised fasting periods lasting 4 to 21 days. The results offer hope for anyone seeking a different path to mental wellness—one that works with your body’s natural healing capacity rather than against it.

What This Research Really Shows

The numbers speak for themselves:

• 93% of participants reported no hunger feelings during their fast
• Both emotional and physical well-being improved significantly across all fasting durations
• 84% of people with pre-existing health complaints reported improvement
• Adverse effects occurred in less than 1% of participants
• Benefits appeared regardless of whether someone fasted for 5 days or 20 days

These aren’t small improvements. Participants consistently rated their emotional well-being higher at the end of their fasting period, with many describing feelings they hadn’t experienced in years—mental clarity, emotional stability, and a renewed sense of vitality.

Why Extended Fasting May Help When Other Approaches Haven’t

Your brain on extended fasting undergoes several important changes:

Metabolic Reset After about 12-24 hours without food, your body shifts from burning glucose to burning fat and producing ketones. Your brain, which normally runs on glucose, begins using these ketones as fuel. Many people describe this as “mental fog lifting”—and there’s solid science behind that feeling.

Inflammation Reduction Chronic low-grade inflammation contributes to depression, anxiety, and cognitive problems. Extended fasting gives your immune system a chance to reset, reducing inflammatory markers that may be affecting your mood and mental clarity.

Stress Response Improvement Rather than adding stress to your system, properly conducted extended fasting actually improves your stress resilience. Your nervous system learns to function in a calmer, more balanced state.

Cellular Renewal During extended fasting, your body activates autophagy—essentially a cellular cleanup process that removes damaged components and regenerates healthy ones. This includes brain cells, potentially explaining improvements in mood and cognitive function.

What to Expect: A Realistic Timeline

Days 1-2: The Adjustment Phase

• Some people experience mild headaches or fatigue as blood sugar stabilizes
• Hunger typically peaks and then begins to diminish
• Sleep may be temporarily disrupted

Days 3-5: The Transition

• Hunger often disappears entirely (this surprises most people)
• Energy levels frequently increase
• Mental clarity often begins to improve
• Some people notice mood lifting

Days 6 and Beyond: The Adaptation

• Physical and emotional well-being continue to improve
• Many report feeling more emotionally stable
• Chronic symptoms often begin to resolve
• Sleep quality typically improves

Who Might Benefit Most

Extended fasting has shown particular promise for people with:

• Treatment-resistant depression or anxiety
• Chronic fatigue and brain fog
• Inflammatory conditions affecting mood
• Metabolic issues contributing to mental health problems
• Multiple health complaints that haven’t responded to conventional treatment

Important Safety Considerations

This approach requires medical supervision. The study participants were monitored by trained physicians throughout their fasting periods. Extended fasting is not appropriate for everyone and should never be attempted without proper medical oversight.

Conditions that typically exclude extended fasting include:

• Active eating disorders
• Pregnancy or breastfeeding
• Severe kidney, liver, or heart disease
• Type 1 diabetes
• Certain medications that require food intake

Getting Started: Your First Steps

1. Find Qualified Medical Support Look for healthcare providers experienced in therapeutic fasting. This might include integrative physicians, naturopathic doctors, or specialized fasting clinics. At our practice, we have both medical supervision and specialized nutritional support to guide you safely through the process.
2. Complete Comprehensive Health Screening Before any extended fast, you’ll need blood work, physical examination, and review of your medical history and current medications.
3. Start with Preparation Most protocols include a preparation phase where you gradually reduce food intake and eliminate processed foods, caffeine, and alcohol.
4. Plan Your Support System Extended fasting works best when you can rest, reduce stress, and focus on the process. Plan accordingly with work and family obligations.

What Makes This Different from Crash Diets

Extended therapeutic fasting under medical supervision is fundamentally different from restrictive dieting:

• It’s time-limited with clear endpoints
• Medical monitoring ensures safety
• The goal is healing, not just weight loss
• Proper refeeding protocols preserve benefits
• It addresses root causes rather than just symptoms

Real-World Application

At our mental health practice, we’ve seen extended fasting help people break free from cycles of treatment resistance and chronic symptoms. Our team includes both psychiatric care and specialized nutritional support to ensure safe, effective fasting protocols. Sarah, a 45-year-old teacher, had struggled with depression and fatigue for years despite trying multiple medications. After a medically supervised 10-day fast, she described feeling “like myself again for the first time in a decade.”

Mark, a veteran with PTSD and chronic pain, found that a 14-day fasting protocol helped both his physical symptoms and his emotional resilience in ways that previous treatments hadn’t achieved.

The Refeeding Process: Equally Important

How you break your fast is crucial for maintaining benefits. The study participants followed a careful 4-day refeeding protocol, gradually reintroducing foods while maintaining the metabolic improvements achieved during fasting. Our nutritionist works closely with patients to develop personalized refeeding plans that support both physical recovery and continued mental health benefits.

Looking Ahead

Extended fasting isn’t a cure-all, but for the right person with proper medical support, it can be a powerful tool for mental health recovery. The research shows us that our bodies have remarkable healing capacity when given the right conditions.

If conventional approaches haven’t provided the relief you’re seeking, extended fasting might offer a path forward. The key is approaching it safely, with qualified medical guidance, and with realistic expectations about the process.

Next Steps

Ready to explore whether extended fasting might help you?

• Schedule a consultation to discuss your health history and goals with our integrated team
• Get comprehensive lab work to assess your current health status
• Work with our nutritionist to develop safe fasting and refeeding protocols
• Receive ongoing medical and nutritional support throughout your fasting journey

Remember: healing takes time, and every person’s journey is different. Extended fasting offers one pathway—backed by solid research—for those ready to explore a different approach to mental wellness.

We combine evidence-based psychiatric care with specialized nutritional support for therapeutic fasting. Our integrated team approach ensures you receive comprehensive care throughout your fasting journey, from preparation through refeeding and long-term maintenance.

Ready to learn more? Contact us to schedule a consultation where we can discuss your specific situation and determine if this approach might be right for you.

This information is for educational purposes and should not replace professional medical advice. Extended fasting should only be undertaken with qualified medical supervision.

References

Berthelot, E., Etchecopar-Etchart, D., Thellier, D., Lancon, C., Aouizerate, B., Courtet, P., … & Boyer, L. (2021). Fasting interventions for stress, anxiety and depressive symptoms: A systematic review and meta-analysis. Nutrients, 13(11), 3947. https://doi.org/10.3390/nu13113947

de Cabo, R., & Mattson, M. P. (2019). Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine, 381(26), 2541-2551. https://doi.org/10.1056/NEJMra1905136

Longo, V. D., & Mattson, M. P. (2014). Fasting: Molecular mechanisms and clinical applications. Cell Metabolism, 19(2), 181-192. https://doi.org/10.1016/j.cmet.2013.12.008

Mattson, M. P., Moehl, K., Ghena, N., Schmaedick, M., & Cheng, A. (2018). Intermittent metabolic switching, neuroplasticity and brain health. Nature Reviews Neuroscience, 19(2), 63-80. https://doi.org/10.1038/nrn.2017.156

Michalsen, A., & Li, C. (2013). Fasting therapy for treating and preventing disease – current state of evidence. Forschende Komplementärmedizin, 20(6), 444-453. https://doi.org/10.1159/000357765

Murta, L., Seixas, D., Harada, L., Damiano, R. F., & Zanetti, M. (2023). Intermittent fasting as a potential therapeutic instrument for major depression disorder: A systematic review of clinical and preclinical studies. International Journal of Molecular Sciences, 24(21), 15551. https://doi.org/10.3390/ijms242115551

Nugraha, B., Riat, A., Ghashang, S. K., Eljurnazi, L., & Gutenbrunner, C. (2020). A prospective clinical trial of prolonged fasting in healthy young males and females—Effect on fatigue, sleepiness, mood and body composition. Nutrients, 12(8), E2281. https://doi.org/10.3390/nu12082281

Skurvydas, A., Istomina, N., Dadeliene, R., Valanciene, D., Majauskiene, D., Mickeviciene, D., … & Brazaitis, M. (2025). Physiological and psychological responses to five-day fasting. PLoS One, 20(6), e0324929. https://doi.org/10.1371/journal.pone.0324929

Stapel, B., Fraccarollo, D., Westhoff-Bleck, M., Widder, J., Bereiter-Hahn, J., Günther, S., … & Bauersachs, J. (2022). Impact of fasting on stress systems and depressive symptoms in patients with major depressive disorder: A cross-sectional study. Scientific Reports, 12(1), 7642. https://doi.org/10.1038/s41598-022-11639-1

Wilhelmi de Toledo, F., Grundler, F., Bergouignan, A., Drinda, S., & Michalsen, A. (2019). Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects. PLoS One, 14(1), e0209353. https://doi.org/10.1371/journal.pone.0209353