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How intermittent fasting can benefit your mental health

Intermittent fasting is normally associated with weight loss and it is indeed a proven weight loss tool, as many have testified. But can it really improve your mental well-being too?

Yes, according to the research. It appears there are two ways in which intermittent fasting (IF) can exert positive effects on mood and cognitive function. The first is by increasing levels of a protein in the brain called brain-derived neurotrophic factor (BDNF). The second is by triggering a process called autophagy.

How it works - BDNF

BDNF is a neuroprotective substance that increases resistance to damage and encourages the growth of new neurons.

Studies have shown that BDNF levels tend to be lower in people with depression, anxiety and major depressive disorder, and the lower levels are, the more severe the symptoms.

One of the ways that BDNF has been shown to enhance mood is by working in concert with the neurotransmitter serotonin. Some antidepressants – the selective serotonin reuptake inhibitors (SSRIs) – work by maintaining levels of serotonin in the brain. Serotonin and BDNF together act 'cooperatively' to enhance brain activity, and impaired signalling between these two substances is thought to be a core feature of depression and anxiety disorders. 

Low levels of BDNF are also associated with various neurological disorders, including Alzheimer’s disease. 

The association with Alzheimer’s disease is probably because BDNF is particularly active in the areas of the brain related to memory, especially the hippocampus.

A 2006 study found that ‘there is strong evidence that BDNF may contribute to the pathogenesis of several neuropsychiatric disorders such as Alzheimer's disease (AD), affective disorders (AFDs), and posttraumatic stress disorder (PTSD).’

How it works - autophagy

The second link between intermittent fasting and mental health is a process called autophagy. Discovered in 2016 by a Japanese cell biologist – who won a Nobel Prize for his efforts – autophagy is a remarkable process that the body uses to give itself what is essentially a good cleanout.

Meaning “self-eating” in Greek, autophagy is often likened to a form of cellular housekeeping. Each cell is capable of destroying or engulfing old or worn-out internal components and taking them to its waste disposal unit within the cell, called the lysosome.

Some of those components include damaged proteins and other debris that are “common features of neurodegenerative diseases”. 

Consider autophagy to be a means of conducting quality control. By weeding out worn-out components, autophagy protects brain cells and slows the advancement of disease.

It’s a marvellous example of biochemical engineering, a detox system that doesn’t require you to buy any special products – you just need to trust the wisdom of your body.

As well as destroying debris, autophagy also disposes of “misfolded” proteins, breaking them down before recycling their parts. A misfolded protein is one that has become defective and misshapen. The danger is that they can start clumping together, something that’s seen in Alzheimer’s disease. Tau protein tangles and Aβ plaques are examples of these wayward proteins that researchers believe are probably the result of autophagy not working properly. 

Woman holding clock and bowl of food

How to make it happen

Fortunately for us all, autophagy is something that doesn’t require medication. All you have to do is stop eating.

When you do so, blood glucose is depleted, and insulin production stops. Insulin suppresses autophagy - when you take a break from eating, insulin declines and autophagy is triggered. Conversely, when you are busy eating and digesting, autophagy is put on hold: the cell is otherwise engaged.

A 2010 study discovered,“One well-recognized way of inducing autophagy is by food restriction.”

What’s more, you don’t have to starve yourself or become malnourished. A simple, short fast will suffice. 

No loss of power

Some people have medical conditions that make fasting inadvisable – for example those with diabetes. But for most people, the body is able to function with no loss of energy during a short fast. When food is not consumed, the body draws on its reserves.

Glucose is stored in muscle and the liver in the form of glycogen. This storage is the equivalent of about 2,000 calories. When you fast, your body draws on this glycogen to provide energy.

Energy may also be released from body fat. After an overnight fast, the body starts to burn fat and ketones, substances that are made from body fat. Ketones provide fuel to the brain in the absence of glucose. That, basically, is why intermittent fasting is so good for fat burning.

New ideas, ancient practice

There’s nothing new about fasting; it’s what humans have done for millennia and for numerous reasons, from health to religious observation. There are also many ways to approach intermittent fasting; there are no hard-and fast-rules, and there are as many variations on this theme as there are reasons to try it. Arguably the most popular is “time-restricted feeding”, where food intake is restricted to a window of around seven hours, for example between 12pm and 7pm. 

Fasting is normal for humans and not a passing fad. It’s what our hunter-gatherer ancestors did, in the absence of shops – they had to be able to make critical decisions and move fast on an empty stomach.

It doesn’t have to be hard: a long overnight fast, beginning with an early evening meal and ending with a late breakfast is an efficient and (for most people) manageable form of time-restricted intermittent fasting.

When you give your body a break, the magic begins and the brain benefits. 

As always, if you are considering changing your diet and food habits, it's always best to do so with the support of a nutrition professional. Feel free to message me if you are considering intermittent fasting.

References

Logan, A.C. and Katzman, M., 2005. Major depressive disorder: probiotics may be an adjuvant therapy. Medical hypotheses, 64(3), pp.533-538.

Mattson, M.P., Maudsley, S. and Martin, B., 2004. BDNF and 5-HT: a dynamic duo in age-related neuronal plasticity and neurodegenerative disorders. Trends in neurosciences, 27(10), pp.589-594.

Zhang, H., Ozbay, F., Lappalainen, J., Kranzler, H.R., van Dyck, C.H., Charney, D.S., Price, L.H., Southwick, S., Yang, B.Z., Rasmussen, A. and Gelernter, J., 2006. Brain derived neurotrophic factor (BDNF) gene variants and Alzheimer's disease, affective disorders, posttraumatic stress disorder, schizophrenia, and substance dependence. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics, 141(4), pp.387-393.

Son, J.H., Shim, J.H., Kim, K.H., Ha, J.Y. and Han, J.Y., 2012. Neuronal autophagy and neurodegenerative diseases. Experimental & molecular medicine, 44(2), pp.89-98.

Alirezaei, M., Kemball, C.C., Flynn, C.T., Wood, M.R., Whitton, J.L. and Kiosses, W.B., 2010. Short-term fasting induces profound neuronal autophagy. Autophagy, 6(6), pp.702-710.

Nutritionist Resource is not responsible for the articles published by members. The views expressed are those of the member who wrote the article.

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Hythe, Kent, CT21

Written by Maria Cross

Hythe, Kent, CT21

I became a nutritional therapist in 1994. Since then, I’ve also been a university lecturer and published two books. I’ve also given many talks and led workshops on the link between diet and health.

I specialise in mental health, but to understand diet and the brain is to understand the gut and all bodily systems - everything is connected.

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