It's true that intermittent fasting may help cut pounds off your weight. However, the diet – in which you restrict the hours you eat in the day – could also slow the hair growth on your head.
That's what has been suggested by a new mouse experiment performed by a team of researchers from Westlake University in Zhejiang, China.
While the mice that followed intermittent fasting showed improved metabolic health, a link was also found between the restrictive eating style and slower hair regeneration.
A similar process might occur in humans, but it is unlikely to be as severe since we have a much slower metabolic rate, as well as different hair growth patterns.
“We don't want to scare people away from practising intermittent fasting because it is associated with a lot of beneficial effects. It's just important to be aware that it might have some unintended effects,” said senior author and stem cell biologist Dr Bing Zhang of Westlake University.
Over time, a variety of links have been found between fasting and health benefits in the body’s supply of blood, muscle tissue and metabolic benefits. However, not much is really known about its effect on hair.
Zhang and his team looked to find out more about this, examining hair regrowth in mice that were shaved and then subjected to different intermittent fasting regimes. While some kept a normal diet, the other mice were permitted 8 hours of food, followed by 16 hours of fasting.
While the mice that followed normal eating routines grew their hair back after 30 days, the fasting group showed only partial hair growth after 96 days.
So why does this happen? The team showed that the slowed hair growth is caused by stress on hair follicle stem cells. Essentially, they are unable to cope with the stress associated with switching from using glucose to fat.
Hair follicles switch between active and dormant phases, and hair grows when these are active. In the control group, the follicles became active around day 20 and stayed active. However, in the intermittent fasting group, long fasting periods caused the follicles to die off.
The team followed the mice study with a small clinical trial on humans. This included 49 healthy young adults. They showed that a time-restricted diet involving 18 hours of fasting each day reduced hair growth by an average of 18 per cent.
However, it should be noted that this study offered only a small sample size and a short testing period. Scientists think that different results may be found in a larger sample.
“The human population is very heterogeneous, so the effects might be different for different people,” says Zhang. “Mice also have a very high metabolic rate compared with humans, so fasting and metabolic switching have a more severe effect on mouse HFSCs.”
The team plans to follow this research by collaborating with hospitals to investigate how fasting impacts other types of stem cells in the skin and other body systems. One of their key focuses is to identify links between fasting and the healing speed of wounds.
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