The Connection between Intermittent Fasting and Brain Health

Overview of intermittent fasting

Intermittent fasting (IF) isn’t just about weight loss but a way of eating that deeply affects one's body and brain. By cycling between periods of eating and fasting, the body shifts from using glucose for energy to burning fat, which triggers various biological changes. These shifts influence metabolism, hormones, and even the way brain cells function.

There are different ways to practice intermittent fasting, but three forms stand out. The 16:8 method limits eating to an 8-hour window and fasting for 16 hours. The 20:4 method narrows that window to just 4 hours, requiring a 20-hour fast. Alternate-day fasting involves fasting every other day, with some variations (Herz et al., 2024). During fasting, insulin levels drop, allowing cells to use stored fat for energy while autophagy (the body’s cellular cleanup process) kicks in. This helps remove damaged cells, reduce inflammation, and promote brain health.

Unlike other eating practices, intermittent fasting cycles between eating and fasting periods focus on when food is consumed rather than strictly reducing calories. While it shares some benefits with the fasting-mimicking diet (FMD) and caloric restriction, the approach differs. FMD allows small amounts of specific nutrients to simulate fasting effects, while caloric restriction involves consistently eating fewer calories without designated fasting periods. Both methods overlap with IF in promoting metabolic and brain health.

Practical considerations for intermittent fasting

Intermittent fasting can support brain function, but it’s important to tailor the approach to each patient’s health status and lifestyle. Here are five key factors to consider when advising patients:

• Fasting periods: Encourage patients to gradually extend fasting windows to help their bodies adjust without extreme discomfort.
• Food intake: Emphasize nutrient-dense meals during eating windows to maintain cognitive function and overall health.
• Hydration: Remind patients to drink enough water and electrolyte-rich fluids to prevent dehydration and support brain function.
• Responses to fasting: Assess mood, energy levels, and mental clarity to determine the appropriate eating pattern.
• Individual risk factors: Patients with diabetes, metabolic disorders, or a history of disordered eating may need modifications or medical supervision.

While intermittent fasting can be useful, it’s not suitable for everyone. You should guide patients in choosing a safe, effective approach that aligns with their medical history and lifestyle.

Benefits of intermittent fasting for brain health

Intermittent fasting supports brain health by offering the following advantages:

Enhances brain metabolism

Intermittent fasting promotes a metabolic shift from glucose to ketone bodies as the primary energy source. In the central nervous system, intermittent fasting enhances stress resistance, synaptic plasticity, and neurogenesis, largely due to increased beta-hydroxybutyrate (BHB) levels (Brocchi et al., 2022). These suggest intermittent fasting may strengthen brain resilience and cognitive function by promoting cellular adaptation and repair.

Reduces inflammation and oxidative stress

Chronic inflammation and oxidative stress are significant risk factors for cognitive decline. Intermittent fasting has been shown to decrease inflammation and enhance antioxidant defenses (Sharsher et al., 2021; University of Cambridge, 2024). These contribute to maintaining brain health and function over time.

Improves insulin sensitivity

Insulin resistance is linked to impaired brain function and an increased risk of neurodegenerative diseases. An intermittent fasting diet can benefit individuals with disrupted glucose and lipid metabolism, helping regulate these processes, support weight loss, and enhance insulin sensitivity (Yuan et al., 2022). This improvement supports cognitive functions and may protect against insulin-related neuronal damage.

Supports neuroplasticity and cognitive function

As the brain ages, its function declines, making aging the leading risk factor for neurodegenerative diseases like dementia and Alzheimer’s disease. Intermittent fasting has been found to increase the production of brain-derived neurotrophic factor (BDNF), a protein crucial for neuroplasticity (Seidler & Barrow, 2022). Elevated BDNF levels enhance the brain's ability to form new neural connections, supporting learning and memory. This adaptability is vital for maintaining cognitive function as we age.

Intermittent fasting's brain-related side effects

Despite the promising benefits of intermittent fasting, it may also lead to some side effects, especially during the adjustment phase. As the body undergoes a metabolic switch from glucose to ketones, some individuals may experience discomfort, such as:

• Brain fog and fatigue: The initial shift in energy sources may cause mental sluggishness and reduced focus.
• Headaches and dizziness: Dehydration and electrolyte imbalances during fasting can contribute to these symptoms.
• Sleep disturbances: Changes in meal timing and fluctuations in human growth hormone levels may affect sleep patterns.
• Difficulty concentrating: Some individuals struggle with focus as their bodies adapt to using ketones for energy.

These side effects are normal and may improve as the body adjusts to intermittent fasting. You can help patients manage these challenges by recommending gradual fasting adjustments and proper hydration.

Conclusion

Intermittent fasting supports brain health by improving metabolism, reducing inflammation, and enhancing cognitive function. This method involves eating within specific time windows, allowing the brain and body to reset and repair. It helps regulate insulin levels, reduce oxidative stress, and promote cellular cleanup. Many people find it beneficial for mental clarity, focus, and overall well-being.

Intermittent fasting may help maintain brain function and slow cognitive decline for those at risk of mild cognitive impairment. However, despite its health benefits, fasting isn’t a one-size-fits-all approach, and individual health conditions should be considered. Healthcare professionals can guide patients in choosing a safe and effective fasting routine. When done correctly, intermittent fasting can be great for long-term brain health.

References

Brocchi, A., Rebelos, E., Dardano, A., Mantuano, M., & Daniele, G. (2022). Effects of intermittent fasting on brain metabolism. Nutrients, 14(6), 1275. https://doi.org/10.3390/nu14061275

Herz, D., Karl, S., Johannes Weiß, Zimmermann, P., Haupt, S., Rebecca Tanja Zimmer, Schierbauer, J., Nadine Bianca Wachsmuth, Maximilian Paul Erlmann, Niedrist, T., Kayvan Khoramipour, Voit, T., Sian Rilstone, Harald Sourij, & Moser, O. (2024). Effects of different types of intermittent fasting interventions on metabolic health in healthy individuals (EDIF): A randomised trial with a controlled-run in phase. Nutrients, 16(8), 1114–1114. https://doi.org/10.3390/nu16081114

Seidler, K., & Barrow, M. (2022). Intermittent fasting and cognitive performance – Targeting BDNF as potential strategy to optimise brain health. Frontiers in Neuroendocrinology, 65(1), 100971. https://doi.org/10.1016/j.yfrne.2021.100971

Sharsher, S. I., Ahmed, A. I., Metwally, M., Arisha, A. H., & Ahmed, K. E. - D. (2021). Intermittent Fasting Decreases Oxidative Stress Parameters and Increases Total Antioxidant Capacity. Biointerface Research in Applied Chemistry, 12(5), 6763–6775. https://doi.org/10.33263/briac125.67636775

University of Cambridge. (2024, January 30). Scientists identify how fasting may protect against inflammation. University of Cambridge. https://www.cam.ac.uk/research/news/scientists-identify-how-fasting-may-protect-against-inflammation

Yuan, X., Wang, J., Yang, S., Gao, M., Cao, L., Li, X., Hong, D., Tian, S., & Sun, C. (2022). Effect of intermittent fasting diet on glucose and lipid metabolism and insulin resistance in patients with impaired glucose and lipid metabolism: A systematic review and meta-analysis. International Journal of Endocrinology, 2022, 1–9. https://doi.org/10.1155/2022/6999907