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What is intermittent fasting? -

Intermittent fasting is a diet in which people only eat during certain hours of the day. There are many different ways of doing it, but a typical schedule might allow for eight hours of eating, 16 hours of fasting.

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Weight loss tool -

Intermittent fasting has been shown to help with weight loss, because it promotes metabolic health. Indeed, there are many stories of people starting on intermittent fasting and watching the pounds drop off.

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Other benefits -

The benefits of intermittent fasting are not limited to boosting the metabolism, however. It has also been shown to improve the stress resistance of stem cells associated with blood, intestinal, and muscle tissue.

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Effect on skin and hair -

Until very recently, however, there was little to no research that looked at how intermittent fasting might affect peripheral tissues, such as skin and hair.

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The study -

Researchers at Westlake University in Zhejiang, China, decided to change that. Researchers conducted a study to look at how intermittent fasting affects hair growth.

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The hypothesis -

The team’s hypothesis was that intermittent fasting may be beneficial for hair regrowth, in the same way that it is beneficial for other systems in the body.

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The experiment -

To test their hypothesis, the team shaved a group of mice and split them into two groups. Each group was subjected to two different intermittent fasting regimes.  

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Test group 1 -

The first group of mice were on a so-called time-restricted feeding (TRF) schedule that involved eight hours of eating, followed by 16 hours of fasting each day.

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Test group 2 -

The second group was on a so-called alternate day feeding (ADF) schedule that allowed them to as much as they wanted, but only every other day.

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The control group -

There was also a control group, which had unlimited access to food and ate as normal for the duration of the experiment.

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Findings -

Contrary to their hypothesis, the researchers found that intermittent fasting actually prohibits hair regrowth. Indeed, there was a considerable difference in the rates of regrowth between the fasting mice and the control group.

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Feeding versus fasting -

Whereas the mice in the control group had regrown most of their hair after 30 days, the mice on both fasting regimes showed only partial regrowth after 96 days.

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Why it happens -

In terms of why this happens, the team believes that it is related to stress on the hair follicle stem cells (HFSCs).

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Under stress -

Essentially, it is thought that HFSCs are unable to cope with the stress of having to constantly switch between using glucose and fat to regrow the hair.

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The active phase -

Indeed, hair follicles switch between active and dormant phases. Hair can only grow when they are in an active phase.

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In the control group -

In the control group of mice, the hair follicles became active on around day 20 of the experiment and then remained active.

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In the test groups -

In the intermittent fasting groups of mice, however, the long periods of fasting caused the hair follicles to die off, thus preventing regrowth.

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What does it mean for humans? -

Intrigued by these results, the researchers decided to conduct a very small clinical trial to see if they would observe the same effects in humans.

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The clinical trial -

The trial involved 49 healthy adults and it showed that a time restricted diet of 18 hours fasting per day can reduce hair growth by an average of 18%.

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Important to note -

It is important to note, however, that the clinical trial used a very small sample size and a very short testing period.

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Bigger experiment, different results? -

If scientists were to test a larger group of people over a longer period, the experiment may well yield very different results.

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Heterogenous human population -

Indeed, the human population is very heterogeneous, so it is possible that the effects could be very different for different groups of people.

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The role of metabolic rate -

It is also important to note that mice have a much higher metabolic rate than humans. This means that the effect of fasting and metabolic is more exaggerated in mice.

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Humans versus mice -

Indeed, the impact of intermittent fasting on hair growth is much milder in humans. Some of the HFSCs survive, meaning hair still grows, just at a slower pace.

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What now? -

Going forward, the same group of researchers plans to work with local hospitals to understand how intermittent fasting affects other regeneration activities in the body.

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Plans to look at skin -

One particular area of interest is how intermittent fasting can affect the skin’s ability to heal after being wounded.

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Other plans -

Another aim of the team is to identify metabolites that could help HFSCs to survive intermittent fasting and therefore reduce the risk of hair growth slowing.

Sources: (News Medical) (Science Focus)

See also: Effects of a fruit-only diet on your body

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