Intermittent fasting can boost metabolism and help people shed pounds. There are studies that have demonstrated the benefits of these popular diet trend. However, a study by Han Chen et al. published in 2024 in the journal Cell revealed a surprising side effect. It appears that skipping meals can slow down hair growth and lead to hair loss.
The Link Between Intermittent Fasting and Slower Hair Growth and Eventual Hair Loss
Background
Chen et al. noted the worldwide popularity of intermittent fasting because of its potential health benefits but also underscored the fact that its impact on somatic stem cells and tissue biology remains unknown. Hence, because previous studies have shown that it can improve the stress resistance of stem cells associated with blood, intestinal, and muscle tissues, the researchers hypothesized that it might also be beneficial for skin tissue regeneration.
They tested this hypothesis by examining hair regrowth in mice that were shaved and then placed under different fasting regimes to monitor hair regrowth. The first group of mice was fed on a time-restricted feeding schedule that involved 8 hours of food access and 16 hours of fasting each day. The second group was placed under an alternate-day feeding schedule. There was also a control group of mice that were given unlimited access to food.
Results showed that fasting inhibited hair regeneration. Mice under the control group demonstrated the most hair regrowth after 30 days. Mice in either the time-restricted feeding schedule group or the alternate-day feeding schedule group demonstrated only partial hair regrowth after 96 days. Chen et al. further investigated the translational potential of these findings in humans by conducting a small clinical trial involving 49 healthy young adults.
The clinical trial indicated that a time-restricted diet, which was characterized by an 18-hour fasting period per day, resulted in an average of 18 percent reduction in hair growth rate compared to the control group after 10 days. It is imperative to consider the limitations inherent in the clinical trial. These included the small sample size and short duration. Hence, to corroborate and validate the findings, larger-scale and longer-duration clinical trials are needed.
Explanations
The study showed that hair growth inhibition occurs because hair follicle stem cells or HFSCs are unable to cope with the oxidative stress associated with switching from using glucose to fat. These stem cells go through phases of activity and dormancy. Hair growth transpires when they are in their active phase and regrowth depends on them becoming active. Intermittent fasting essentially induced apoptosis or programmed cell death in activated HFSCs.
Note that the inhibited hair follicle regeneration from apoptosis is not due to common effects of fasting like calorie reduction, changes in circadian rhythms, and changes in the mTORC1 nutrient-sensing pathway that regulates cell growth and metabolism in response to nutrient availability. Fasting specifically triggers communication between the adrenal glands and dermal adipocytes or fat cells in the skin. This is an example of interorgan communication.
The specific interorgan communication results in the rapid release of free fatty acids near the hair follicles. These fatty acids disrupt specific HFSC metabolism and result further in increased oxidative stress due to the elevated level or buildup of reactive oxygen species and cause damage and apoptosis. Hair follicle stem cells, unlike epidermal stem cells which have higher antioxidant capacity, also do not have natural mechanisms to use free fatty acids.
Chen et al. highlighted a novel inhibitory effect of intermittent fasting on tissue regeneration that is mediated by disrupted metabolic stability in certain stem cell niches like the HFSC niche during nutrient instability. Their research underscored the role of interorgan communication in regulating stem cell activity under stress conditions. Further studies are recommended since humans have a slower metabolic rate and the human population is very heterogeneous.
FURTHER READINGS AND REFERENCES
- Chen, H., Liu, C., Cui, S., Xia, Y., Zhang, K., Cheng, H., Peng, J., Yu, X., Li, L., Yu, H., Zhang, J., Zheng, J.-S., and Zhang, B. 2024. “Intermittent Fasting Triggers Interorgan Communication to Suppress Hair Follicle Regeneration. Cell. Elsevier BV. DOI: 1016/j.cell.2024.11.004