Recent research published in the journal Cell explores the impact of intermittent fasting (IF) on hair regrowth, revealing surprising consequences for metabolic health. While intermittent fasting has previously been associated with numerous benefits including improved metabolic health and stress resistance, this study uncovers potential drawbacks regarding the rejuvenation of hair follicles.

The Study: Fasting and Hair Regrowth

In the study conducted by a team of researchers at Westlake University in Zhejiang, China, evidence was gathered from both murine models and a small clinical trial involving human participants. Key findings suggest that while intermittent fasting enhances metabolic health, it can simultaneously hinder hair regeneration.

During the experiment, mice were divided into groups with different feeding schedules: some were placed on a time-restricted feeding (TRF) regimen of eight hours of food access followed by 16 hours of fasting, while others had the option for feeding every other day (alternate-day feeding or ADF).

Findings: Hair Growth Implications

The results were striking. After 30 days, control mice with constant food access nearly fully regrew their hair, while those subjected to intermittent fasting displayed only partial regrowth after 96 days.

This phenomenon was attributed to the behavior of hair follicle stem cells (HFSCs), which struggled to manage oxidative stress when transitioning from glucose to fat metabolism during fasting. Critical observations made included:

Finding Description
Activation of HFSCs HFSCs in control mice became activated around day 20 post-shaving and facilitated hair regrowth.
Apoptosis in HFSCs During extended fasting, HFSCs in fasting groups underwent apoptosis, limiting hair regeneration.
Free Fatty Acids Upon fasting initiation, free fatty acids released entered the HFSCs, impairing their functionality.

Furthermore, a small-scale clinical trial with 49 healthy adults indicated that a time-restricted diet involving 18 hours of fasting led to an 18% reduction in hair growth speed when compared to control subjects. However, researchers caution that more extensive studies are necessary to confirm these potential effects, given the diversity of human hair growth patterns and metabolic rates.

Understanding the Underlying Mechanisms

One of the significant findings was the differential behavior of epidermal stem cells, which remained unaffected by the fasting-induced environment. This resilience can be attributed to their higher antioxidant capacity, in contrast to the HFSCs.

Stem Cell Type Response to Fasting
Hair Follicle Stem Cells (HFSCs) Underwent increased apoptosis, leading to hindered hair regrowth.
Epidermal Stem Cells Remained stable with no adverse effects due to their superior antioxidant capabilities.

To mitigate the negative effects of fasting on HFSCs, researchers demonstrated that both topical antioxidant application, specifically vitamin E, and genetically enhancing the antioxidant levels within HFSCs promoted their survival during fasting periods. This offers potential avenues for future work to support hair regrowth during fasting.

Future Research Directions

Looking ahead, the research team intends to collaborate with hospitals to explore how intermittent fasting affects other types of stem cells associated with skin and various body systems. Potential areas for future investigation include:

  • Exploring the impact of fasting on skin wound healing.
  • Identifying metabolites that might facilitate HFSC survival during fasting.
  • Expanding clinical studies to more robustly assess the implications of fasting on hair growth among diverse populations.

These explorations may elucidate comprehensive strategies for optimizing fasting benefits while minimizing negative side effects, potentially leading to new insights in regenerative medicine.

References

[1] Zhang, B. et al. (2024). An unexpected side effect: Intermittent fasting may slow hair regrowth. Cell. DOI: 10.1016/j.cell.2024.11.004

[2] Lifespan.io