Does intermittent fasting have benefits for our brain?

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Intermittent fasting has become a popular dietary approach to help people lose or manage their weight. It has also been promoted as a way to reset metabolism, control chronic disease, slow ageing and improve overall health.

Meanwhile, some research suggests intermittent fasting may offer a different way for the brain to access energy and provide protection against neurodegenerative diseases like Alzheimer’s disease.

This is not a new idea – the ancient Greeks believed fasting enhanced thinking. But what does the modern-day evidence say?

First, what is intermittent fasting?

Our diets – including calories consumed, macronutrient composition (the ratios of fats, protein and carbohydrates we eat) and when meals are consumed – are factors in our lifestyle we can change. People do this for cultural reasons, desired weight loss or potential health gains.

Intermittent fasting consists of short periods of calorie (energy) restriction where food intake is limited for 12 to 48 hours (usually 12 to 16 hours per day), followed by periods of normal food intake. The intermittent component means a re-occurrence of the pattern rather than a “one off” fast.

Food deprivation beyond 24 hours typically constitutes starvation. This is distinct from fasting due to its specific and potentially harmful biochemical alterations and nutrient deficiencies if continued for long periods.

4 ways fasting works and how it might affect the brain

The brain accounts for about 20% of the body’s energy consumption.

Here are four ways intermittent fasting can act on the body which could help explain its potential effects on the brain.

1. Ketosis

The goal of many intermittent fasting routines is to flip a “metabolic switch” to go from burning predominately carbohydrates to burning fat. This is called ketosis and typically occurs after 12–16 hours of fasting, when liver and glycogen stores are depleted. Ketones – chemicals produced by this metabolic process – become the preferred energy source for the brain.

Due to this being a slower metabolic process to produce energy and potential for lowering blood sugar levels, ketosis can cause symptoms of hunger, fatigue, nausea, low mood, irritability, constipation, headaches, and brain “fog”.

At the same time, as glucose metabolism in the brain declines with ageing, studies have shown ketones could provide an alternative energy source to preserve brain function and prevent age-related neurodegeneration disorders and cognitive decline.

Consistent with this, increasing ketones through supplementation or diet has been shown to improve cognition in adults with mild cognitive decline and those at risk of Alzheimer’s disease respectively.

2. Circadian syncing

Eating at times that don’t match our body’s natural daily rhythms can disrupt how our organs work. Studies in shift workers have suggested this might also make us more prone to chronic disease.

Time-restricted eating is when you eat your meals within a six to ten-hour window during the day when you’re most active. Time-restricted eating causes changes in expression of genes in tissue and helps the body during rest and activity.

A 2021 study of 883 adults in Italy indicated those who restricted their food intake to ten hours a day were less likely to have cognitive impairment compared to those eating without time restrictions.

older man playing chess
Matching your eating to the active parts of your day may have brain benefits.
Shutterstock

3. Mitochondria

Intermittent fasting may provide brain protection through improving mitochondrial function, metabolism and reducing oxidants.

Mitochondria’s main role is to produce energy and they are crucial to brain health. Many age-related diseases are closely related to an energy supply and demand imbalance, likely attributed to mitochondrial dysfunction during ageing.

Rodent studies suggest alternate day fasting or reducing calories by up to 40% might protect or improve brain mitochondrial function. But not all studies support this theory.

4. The gut-brain axis

The gut and the brain communicate with each other via the body’s nervous systems. The brain can influence how the gut feels (think about how you get “butterflies” in your tummy when nervous) and the gut can affect mood, cognition and mental health.

In mice, intermittent fasting has shown promise for improving brain health by increasing survival and formation of neurons (nerve cells) in the hippocampus brain region, which is involved in memory, learning and emotion.

medical clinician shows woman a sheet of brain scans
What we eat can affect our brain, and vice versa.
Shutterstock

There’s no clear evidence on the effects of intermittent fasting on cognition in healthy adults. However one 2022 study interviewed 411 older adults and found lower meal frequency (less than three meals a day) was associated with reduced evidence of Alzheimer’s disease on brain imaging.

Some research has suggested calorie restriction may have a protective effect against Alzheimer’s disease by reducing oxidative stress and inflammation and promoting vascular health.

When we look at the effects of overall energy restriction (rather than intermittent fasting specifically) the evidence is mixed. Among people with mild cognitive impairment, one study showed cognitive improvement when participants followed a calorie restricted diet for 12 months.

Another study found a 25% calorie restriction was associated with slightly improved working memory in healthy adults. But a recent study, which looked at the impact of calorie restriction on spatial working memory, found no significant effect.

Bottom line

Studies in mice support a role for intermittent fasting in improving brain health and ageing, but few studies in humans exist, and the evidence we have is mixed.

Rapid weight loss associated with calorie restriction and intermittent fasting can lead to nutrient deficiencies, muscle loss, and decreased immune function, particularly in older adults whose nutritional needs may be higher.

Further, prolonged fasting or severe calorie restriction may pose risks such as fatigue, dizziness, and electrolyte imbalances, which could exacerbate existing health conditions.

If you’re considering intermittent fasting, it’s best to seek advice from a health professional such as a dietitian who can provide guidance on structuring fasting periods, meal timing, and nutrient intake. This ensures intermittent fasting is approached in a safe, sustainable way, tailored to individual needs and goals.The Conversation

Hayley O’Neill, Assistant Professor, Faculty of Health Sciences and Medicine, Bond University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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  • Cancer is increasingly survivable – but it shouldn’t depend on your ability to ‘wrangle’ the health system

    10almonds is reader-supported. We may, at no cost to you, receive a portion of sales if you purchase a product through a link in this article.

    One in three of us will develop cancer at some point in our lives. But survival rates have improved to the point that two-thirds of those diagnosed live more than five years.

    This extraordinary shift over the past few decades introduces new challenges. A large and growing proportion of people diagnosed with cancer are living with it, rather than dying of it.

    In our recently published research we examined the cancer experiences of 81 New Zealanders (23 Māori and 58 non-Māori).

    We found survivorship not only entailed managing the disease, but also “wrangling” a complex health system.

    Surviving disease or surviving the system

    Our research focused on those who had lived longer than expected (four to 32 years since first diagnosis) with a life-limiting or terminal diagnosis of cancer.

    Common to many survivors’ stories was the effort it took to wrangle the system or find others to advocate on their behalf, even to get a formal diagnosis and treatment.

    By wrangling we refer to the practices required to traverse complex and sometimes unwelcoming systems. This is an often unnoticed but very real struggle that comes on top of managing the disease itself.

    The common focus of the healthcare system is on symptoms, side effects of treatment and other biological aspects of cancer. But formal and informal care often falls by the wayside, despite being key to people’s everyday experiences.

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    Survival is often linked to someone’s social connections and capacity to access funds. Getty Images

    The inequities of cancer survivorship are well known. Analyses show postcodes and socioeconomic status play a strong role in the prevalence of cancer and survival.

    Less well known, but illustrated in our research, is that survival is also linked to people’s capacity to manage the entire healthcare system. That includes accessing a diagnosis or treatment, or identifying and accessing alternative treatments.

    Survivorship is strongly related to material resources, social connections, and understandings of how the health system works and what is available. For instance, one participant who was contemplating travelling overseas to get surgery not available in New Zealand said:

    We don’t trust the public system. So thankfully we had private health insurance […] But if we went overseas, health insurance only paid out to $30,000 and I think the surgery was going to be a couple of hundred thousand. I remember Dad saying and crying and just being like, I’ll sell my business […] we’ll all put in money. It was really amazing.

    Assets of survivorship

    In New Zealand, the government agency Pharmac determines which medications are subsidised. Yet many participants were advised by oncologists or others to “find ways” of taking costly, unsubsidised medicines.

    This often meant finding tens of thousands of dollars with no guarantees. Some had the means, but for others it meant drawing on family savings, retirement funds or extending mortgages. This disproportionately favours those with access to assets and influences who survives.

    But access to economic capital is only one advantage. People also have cultural resources – often described as cultural capital.

    In one case, a participant realised a drug company was likely to apply to have a medicine approved. They asked their private oncologist to lobby on their behalf to obtain the drug through a compassionate access scheme, without having to pay for it.

    Others gained community support through fundraising from clubs they belonged to. But some worried about where they would find the money, or did not want to burden their community.

    I had my doctor friend and some others that wanted to do some public fundraising. But at the time I said, “Look, most of the people that will be contributing are people from my community who are poor already, so I’m not going to do that option”.

    Accessing alternative therapies, almost exclusively self-funded, was another layer of inequity. Some felt forced to negotiate the black market to access substances such as marijuana to treat their cancer or alleviate the side effects of orthodox cancer treatment.

    Cultural capital is not a replacement for access to assets, however. Māori survivorship was greatly assisted by accessing cultural resources, but often limited by lack of material assets.

    Persistence pays

    The last thing we need when faced with the possibility of cancer is to have to push for formal diagnosis and care. Yet this was a common experience.

    One participant was told nothing could be found to explain their abdominal pain – only to find later they had pancreatic cancer. Another was told their concerns about breathing problems were a result of anxiety related to a prior mental health history, only to learn later their earlier breast cancer had spread to their lungs.

    Persistence is another layer of wrangling and it often causes distress.

    Once a diagnosis was given, for many people the public health system kicked in and delivered appropriate treatment. However, experiences were patchy and variable across New Zealand.

    Issues included proximity to hospitals, varying degrees of specialisation available, and the requirement of extensive periods away from home and whānau. This reflects an ongoing unevenness and lack of fairness in the current system.

    When facing a terminal or life-limiting diagnosis, the capacity to wrangle the system makes a difference. We shouldn’t have to wrangle, but facing this reality is an important first step.

    We must ensure it doesn’t become a continuing form of inequity, whereby people with access to material resources and social and cultural connections can survive longer.

    Kevin Dew, Professor of Sociology, Te Herenga Waka — Victoria University of Wellington; Alex Broom, Professor of Sociology & Director, Sydney Centre for Healthy Societies, University of Sydney; Chris Cunningham, Professor of Maori & Public Health, Massey University; Elizabeth Dennett, Associate Professor in Surgery, University of Otago; Kerry Chamberlain, Professor of Social and Health Psychology, Massey University, and Richard Egan, Associate Professor in Health Promotion, University of Otago

    This article is republished from The Conversation under a Creative Commons license. Read the original article.

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  • How To Plan For The Unplannable

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    How To Always Follow Through

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    Now my socks are wet.❞

    ~ with apologies to Robert Frost

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    We’ve written before on bolstering flagging motivation when all is as expected but we just need an extra boost:

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    …but what about when the unexpected happens?

    First rule: wear a belt and suspenders

    Not literally, unless that’s your thing. But you might have heard this phrase from the business world, and it applies to healthful practices too:

    If your primary plan fails, you need a second one already in place.

    In business, we see this as “business continuity management”. For example, your writer here, I have backups for every important piece of tech I own, Internet connections from two different companies in case one goes down, and if there’s a power cut, I have everything accessible and sync’d on a fully-charged tablet so I can complete my work there if necessary. And yes, I have low-tech coffee-brewing equipment too.

    In health, we should be as serious. We all learned back in 2020 that grocery stores and supply chains can fail; how do we eat healthily when all that is on sale is an assortment of random odds and ends? The answer, as we now know because hindsight really is 2020 in this case, is to keep a well-stocked pantry of healthy things with a long shelf life. Also a good stock of whatever supplements we take, and medicines, and water. And maintain them and rotate the stock!

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    Science of Pilates: Understand the Anatomy and Physiology to Perfect Your Practice – by Tracy Ward

    Second rule: troubleshoot up front

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    You can read a bit more about some of this here, the below article was written about facing depression and anxiety, but if you can enact your plans when unmotivated and fearful, then you will surely be able to enact them when not, so this information is good anyway:

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    Third rule: don’t err the same way twice

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    How To Break Out Of Cycles Of Self-Sabotage, And Stop Making The Same Mistakes

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  • This Is When Your Muscles Are Strongest

    10almonds is reader-supported. We may, at no cost to you, receive a portion of sales if you purchase a product through a link in this article.

    Dr. Karyn Esser is a professor in the Department of Physiology and Aging at the University of Florida, where she’s also the co-director of the University of Florida Older Americans Independence Center, and she has insights to share on when it’s best to exercise:

    It’s 4–5pm

    Surprise, no clickbait or burying the lede!

    This goes regardless of age or sex, but as we get older, it’s common for our circadian rhythm to weaken, which may result in a tendency to fluctuate a bit more.

    However, since it’s healthy to keep one’s circadian rhythm as stable as reasonably possible, this is a good reason to try to keep our main exercise focused around that time of day, as it provides a sort of “anchor point” for the rest of our day to attach to, so that our body can know what time it is relative to that.

    It’s also the most useful time of day to exercise, because most exercises give benefits proportional to progressive overloading, so training at our peak efficiency time will give the most efficient results. So much for those 5am runs!

    On which note: while the title says “strongest” and the thumbnail has dumbbells, this does go for all different types of exercises that have been tested.

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    There was a very illustrative study done specifically for this, though!

    ❝65 subjects with moderate acne ate either a bar containing ten times the amount of chocolate in a typical bar, or an identical-appearing bar which contained no chocolate. Counting of all the lesions on one side of the face before and after each ingestion period indicated no difference between the bars.

    Five normal subjects ingested two enriched chocolate bars daily for one month; this represented a daily addition of the diet of 1,200 calories, of which about half was vegetable fat. This excessive intake of chocolate and fat did not alter the composition or output of sebum.

    A review of studies purporting to show that diets high in carbohydrate or fat stimulate sebaceous secretion and adversely affect acne vulgaris indicates that these claims are unproved.

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  • Survival of the Prettiest – by Dr. Nancy Etcoff

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