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Fasting and brain health

Many people are aware of the benefits of fasting on weight and blood sugar/cholesterol

But did you know fasting can directly boost brain function, independent of diet and lifestyle?

Fasting has long been a part of many cultures, as a way to help cognition and brain function

Ancient Greeks would regularly fast to improve mental agility, and great 'thinkers' would often fast when struggling with a problem. Egyptians, Babylonians, and Mongolian cultures also used fasting as a way to purify the mind. Many cultures still practice ritualistic fasting, ie Ramadan, lent, yom kippur, jain, and Buddhist fasting

Scientists believe that humans evolved to go without food for extended periods of time (when resources were scarce), and preserving and protecting brain function became the bodies priority.

Fasting triggers the body to start using fat for energy (ketosis) instead of glucose

When fasts are broken, the 'metabolic switch' that occurs triggers off a process that can build brain function and damage resilience (1)


  • Stimulates autophagy (killing off old damaged cells, allowing new brain growth) Improves insulin levels and blood sugar (there is a direct correlation between lower insulin levels and improved memory - think of the 'brain fog' that occurs after a sugary snack)

  • Increases BDNF ( a protein that stimulates brain growth and function)

  • Reduces inflammation levels, (linked with cognitive impairment and neurological disease) (1, 3)

  • It may even help prevent Alzheimers disease, via increasing levels of a protein called hsp-70, which clears away the amyloid plaques/tau proteins responsible for Alzheimers (2)

Many people report a calmer clearer mind and better sleep, with fasting/ time restricted eating, with studies confirming this

In animal trials, mice that were deprived of food for 12-14h/day (ie time restricted eating) showed evidence of

  • new brain cell formation (4)

  • increased levels of ghrelin (hunger hormone), which triggered brain growth (1)

  • more active brains (1)

Early research also shows fasting/intermittent ketosis may help with parkinsons disease, and with recovery from stroke and head injury (1,6,7)

Fasting is not recommended for everyone - if you are pregnant, underweight, or have a history of eating disorders then it's not advised to fast Similarly children should not undertake any form of fasting or ketogenic diets without close medical supervision (ketogenesis is used for some very selective medical conditions in children but should NOT be done outside of this and NOT without very close dietician and specialist input)

If you are undergoing chemotherapy, are on immunosuppressive medicine, or multiple medications please talk to your doctor to see if it is safe for you to fast

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