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.
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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.
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.
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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When You “Should” Be In Better Shape
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It’s easy to think that we “should” be many things that we aren’t. However, it can be counterproductive to implementing real change:
The problem with “should”
The word “should” often sabotages changes in mindset and habit formation. Saying things like “I should be further along” typically leads to frustration, feelings of failure, and ultimately a lack of motivation to take action. Yes, in the first instance, “I should…” can be a motivator, but when your goals are not achieved by the second session, and the “I should…” is still there, the subconscious says “well, clearly this is not working”. Even though the conscious mind can easily see the fallacy in that dysfunctional line of thinking, the subconscious is easily swayed by such things, and in turn easily sways our actual behaviors.
Also, even before that, if goals feel impossible, people often do nothing instead of making small, manageable changes.
So, what should we do instead?
Step 1: assess your current lifestyle and priorities. Your current results are a reflection of past habits and actions, including dieting practices, inconsistent workouts, and lack of planning. Instead of searching for a “perfect plan,” first acknowledge your current lifestyle and priorities. Then, identify which habits are beneficial, which ones hold you back, and what common excuses you make. By understanding where you are now, you can create a sustainable plan that fits your life rather than fighting against it.
Step 2: define your future lifestyle. It’s not enough to just set goals—you need to define what the lifestyle associated with those goals looks like. Recognize that real change requires adjustments in habits and routines. Don’t stress over whether these changes feel overwhelming; simply identify what might be necessary. Writing things down (and then consulting them often, not just putting them away never to be seen again) makes them more tangible and helps create a roadmap for progress.
Step 3: make one small change today. Rather than making vague or overwhelming changes, start with one small, realistic step that aligns with your goals. Building momentum through cumulatively beneficial small actions leads to longer-lasting motivation. Also, instead of focusing on what you need to cut out, look for positive habits to add, as this makes change easier. Track your progress visibly—like using a checklist—and commit to revisiting and adding new changes weekly.
For more on all of this, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like:
How To Plan For The Unplannable And Always Follow Through
Take care!
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The Humor Habit – by Paul Osincup
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Ask not for whom the bell tolls… It could be tolling for anyone. Don’t worry about it.It’s probably fine.
More seriously (heh), laughter is good for healthy lifespan, also called healthspan. It eases stress and anxiety, gives our brains neurochemicals they need to function well, and is very pro-social too, which in turn has knock-on positive effects for our own mental health as well as those around us.
This book is a guide to cultivating that humor, finding the funny side in difficult times, and bringing a light-hearted silliness to moments where it helps.
The title suggests it’s about habit-building (and it is!) but it’s also about knowing where to look in your daily life for humorous potential and how to find it, and how to bring that into being in the moment.
The style is that of an instruction manual with a healthy dose of pop-science; first and foremost this is a practical guide, not a several-hundred page exhortation on “find things funny!”, but rather a “hey, psst, here are many sneaky insider tricks for finding the funny“.
Bottom line: this book is not only a very enjoyable read, but also very much the gift that keeps on giving, so treat yourself!
Click here to check out The Humor Habit, and strength your funny-bones!
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How Not To Get Sick: A Cookbook – by Dr. Benjamin Bikman and Diana Keuilian
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We’ve previously reviewed Dr. Bikman’s excellent “Why We Get Sick”, and if you haven’t read that yet, we recommend doing so.
Nevertheless, you don’t need to have read it to benefit from this one, which is about cooking with those learnings (from the other book) in mind.
Before getting to the recipes, we get a section recapping what we learned previously, as well as adding some more general lifestyle advices beyond the kitchen. The science is also expanded a bit, to include such things as the two-way relationship between insulin and aging, as well as the interplay with other metrics of health, including blood lipids, for example.
The authors then provide a plan, in the three stages: reverse (insulin resistance), prevent (insulin resistance), maintain (insulin sensitivity).
The recipes themselves, of which there are 70, are of course tailored to do the above three things; they’re also quite diverse, albeit if you are vegetarian or vegan, you should know in advance that most of these recipes are not.
Bottom line: if the above doesn’t apply to you, and you would like to improve your insulin sensitivity, this book can indeed help.
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Unprocess Your Life – by Rob Hobson
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Rob Hobson is not a doctor, but he is a nutritionist with half the alphabet after his name (BSc, PGDip, MSc, AFN, SENR) and decades of experience in the field.
The book covers, in jargon-free fashion, the science of ultra-processed foods, and why for example that pack of frozen chicken nuggets are bad but a pack of tofu (which obviously also took some processing, because it didn’t grow on the plant like that) isn’t.
This kind of explanation puts to rest a lot of the “does this count?” queries that a reader might have when giving the shopping list a once-over.
He also covers practical considerations such as kitchen equipment that’s worth investing in if you don’t already have it, and an “unprocessed pantry” shopping list.
The recipes (yes, there are recipes, nearly a hundred of them) are not plant-based by default, but there is a section of vegan and vegetarian recipes. Given that the theme of the book is replacing ultra-processed foods, it doesn’t mean a life of abstemiousness—there are recipes for all manner of things from hot sauce to cakes. Just, healthier unprocessed ones! There are classically healthy recipes too, of course.
Bottom line: if you’ve been wishing for a while that you could get rid of those processed products that are just so convenient that you haven’t got around to replacing them with healthier options, this book can indeed help you do just that.
Click here to check out Unprocess Your Life, and unprocess your life!
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Invigorating Sabzi Khordan
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Have you ever looked at the nutritional values and phytochemical properties of herbs, and thought “well that’s all well and good, but we only use a tiny amount”? Sabzi khordan is a herb-centric traditional Levantine sharing platter served most commonly as an appetizer, and it is indeed appetizing! Never again will “start your meal with a green salad to ensure a gentle blood sugar curve” seem like a chore:
You will need
- Large bunch of parsley
- Small bunch of tarragon leaves
- Small bunch of basil leaves
- Small bunch of mint
- Small bunch of sorrel leaves
- 7 oz block of feta cheese (if vegan, a plant-based substitution is fine in culinary terms, but won’t have the same gut-healthy benefits, as plant-based cheeses are not fermented)
- 9 oz labneh-stuffed vine leaves in olive oil (if vegan, same deal as the above, except it’s harder to find plant-based substitutes for labneh (strained yogurt cheese), so you might want to use our Plant-Based Healthy Cream Cheese recipe instead and make your own)
- 2 tbsp za’atar (you can make your own by blending dried hyssop, dried sumac berries, sesame seeds, dried thyme, and salt—but if you haven’t had za’atar before, we recommend first buying some like the one that we linked, so that next time you know what you’re aiming for)
- 3 tbsp extra virgin olive oil
- 10 radishes
- 6 scallions
- 9 oz walnuts, soaked in water overnight and drained
- 1 cucumber, cut into batons
- Warm flatbreads (you can use our Healthy Homemade Flatbreads recipe)
Method
(we suggest you read everything at least once before doing anything)
1) Arrange the feta, labneh, za’atar, and olive oil in separate little serving dishes.
2) Arrange everything else around them on a platter.
3) Serve! You may be thinking: did we really need a recipe to tell us “put the things on a plate”? The answer here is that this one today was shared mostly as a matter of inspiration, because when was the last time you thought to serve herbs as the star of the dish? Plus, it’s an excuse to try za’atar, not something so commonly seen outside of the Levant.
An alternative presentation
Enjoy!
Want to learn more?
For those interested in some of the science of what we have going on today:
- Herbs for Evidence-Based Health & Healing
- Making Friends With Your Gut (You Can Thank Us Later)
- 10 Ways To Balance Blood Sugars
Take care!
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Demystifying Cholesterol
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All About Cholesterol
When it comes to cholesterol, the most common lay understanding (especially under a certain age) is “it’s bad”.
A more informed view (and more common after a certain age) is “LDL cholesterol is bad; HDL cholesterol is good”.
A more nuanced view is “LDL cholesterol is established as significantly associated with (and almost certainly a causal factor of) atherosclerotic cardiovascular disease and related mortality in men; in women it is less strongly associated and may or may not be a causal factor”
You can read more about that here:
Statins: His & Hers? ← we highly recommend reading this, especially if you are a woman and/or considering/taking statins. To be clear, we’re not saying “don’t take statins!”, because they might be the right medical choice for you and we’re not your doctors. But we are saying: here’s something to at least know about and consider.
Beyond HDL & LDL
There is also VLDL cholesterol, which as you might have guessed, stands for “very low-density lipoprotein”. It has a high, unhealthy triglyceride content, and it increases atherosclerotic plaque. In other words, it hardens your arteries more quickly.
The term “hardening the arteries” is an insufficient descriptor of what’s happening though, because while yes it is hardening the arteries, it’s also narrowing them. Because minerals and detritus passing through in the blood (the latter sounds bad, but there is supposed to be detritus passing through in the blood; it’s got to get out of the body somehow, and it’s off to get filtered and excreted) get stuck in the cholesterol (which itself is a waxy substance, by the way) and before you know it, those minerals and other things have become a solid part of the interior of your artery wall, like a little plastering team came and slapped plaster on the inside of the walls, then when it hardened, slapped more plaster on, and so on. Macrophages (normally the body’s best interior clean-up team) can’t eat things much bigger than themselves, so that means they can’t tackle the build-up of plaque.
Impact on the heart
Narrower less flexible arteries means very poor circulation, which means that organs can start having problems, which obviously includes your heart itself as it is not only having to do a harder job to keep the blood circulating through the narrower blood vessels, but also, it is not immune to also being starved of oxygen and nutrients along with the rest of the body when the circulation isn’t good enough. It’s a catch 22.
What if LDL is low and someone is getting heart disease anyway?
That’s often a case of apolipoprotein B, and unlike lipoprotein A, which is bound to LDL so usually* isn’t a problem if LDL is in “safe” ranges, Apo-B can more often cause problems even when LDL is low. Neither of these are tested for in most standard cholesterol tests by the way, so you might have to ask for them.
*Some people, around 1 in 20 people, have hereditary extra risk factors for this.
What to do about it?
Well, get those lipids tests! Including asking for the LpA and Apo-B tests, especially if you have a history of heart disease in your family, or otherwise know you have a genetic risk factor.
With or without extra genetic risks, it’s good to get lipids tests done annually from 40 onwards (earlier, if you have extra risk factors).
See also: Understanding your cholesterol numbers
Wondering whether you have an increased genetic risk or not?
Genetic Testing: Health Benefits & Methods ← we think this is worth doing; it’s a “one-off test tells many useful things”. Usually done from a saliva sample, but some companies arrange a blood draw instead. Cost is usually quite affordable; do shop around, though.
Additionally, talk to your pharmacist to check whether any of your meds have contraindications or interactions you should be aware of in this regard. Pharmacists usually know contraindications/interactions stuff better than doctors, and/but unlike doctors, they don’t have social pressure on them to know everything, which means that if they’re not sure, instead of just guessing and reassuring you in a confident voice, they’ll actually check.
Lastly, shocking nobody, all the usual lifestyle medicine advice applies here, especially get plenty of moderate exercise and eat a good diet, preferably mostly if not entirely plant-based, and go easy on the saturated fat.
Note: while a vegan diet contains zero dietary cholesterol (because plants don’t make it), vegans can still get unhealthy blood lipid levels, because we are animals and—like most animals—our body is perfectly capable of making its own cholesterol (indeed, we do need some cholesterol to function), and it can make its own in the wrong balance, if for example we go too heavy on certain kinds of (yes, even some plant-based) saturated fat.
Read more: Can Saturated Fats Be Healthy? ← see for example how palm oil and coconut oil are both plant-based, and both high in saturated fat, but palm oil’s is heart-unhealthy on balance, while coconut oil’s is heart-healthy on balance (in moderation).
Want to know more about your personal risk?
Try the American College of Cardiology’s ASCVD risk estimator (it’s free)
Take care!
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