Fasting and Brain Function – Fasting 24

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How does fasting affect brain function? There is very little reliable human data, but some very interesting animal data, as recently reviewed. There are many potential benefits. While I tend to focus on weight loss and type 2 diabetes, there are many other benefits, including autophagy (a cellular cleansing process), lipolysis (fat burning), anti aging effects and anti-seizure effects.IF Effects

From an evolutionary standpoint, we can look at other mammals for some clues. In many mammals, the body responds to severe caloric deprivation with a reduction in the size of all organs with two prominent exceptions – the brain and the male testicles. This suggests that cognitive function is highly preserved.

This makes quite a lot of sense from an evolutionary standpoint. Suppose you had some trouble finding food. If your brain started to slow down, well, the mental fog would make it that much harder to find food. Our brainpower, one of the main advantages we have in the natural world, would be squandered. No, the brain maintains or even boosts its abilities. In stories of Japanese prisoners of war in World War II (Unbroken by Laura Hillenbrand), many have described the amazing clarity of thought that often accompanies starvation.

The preservation of the size of the testicles is also a significant advantage in trying to pass on our genes to the next generation.

In all mammals, one of the highly preserved behavioural traits is that mental activity increases when hungry and decreases with satiation. Of course, we have all experienced this. Sometimes this is called ‘food coma’. Think about that large Thanksgiving turkey and pumpkin pie. After that huge meal, are we mentally sharp as a tack? or dull as a concrete block? How about he opposite? Think about a time that you were really hungry. Were you tired and slothful? I doubt it. Your senses were probably hyper-alert and you were mentally sharp as a needle. That is to say that there is likely a large survival advantage to animals that are cognitively sharp, as well as physically agile during times of food scarcity.foodcoma

Studies have also proven that mental acuity does not decrease with fasting. One study compared cognitive tasks at baseline and after a 24 hour fast. None of the tasks – including sustained attention, attentional focus, simple reaction time or immediate memory were found to be impaired. Another double-blinded study of a 2-day ‘almost total’ caloric deprivation found no detrimental effect even after repeatedly testing cognitive performance, activity, sleep and mood.

What we say we are ‘hungry’ for something (hungry for power, hungry for attention), does it mean we are slothful and dull? No, it means that we are hyper-vigilant and energetic. So, fasting and hunger clearly activate us towards our goal. People always worry that fasting will dull their senses, but in fact, it has the opposite, energizing effect.

These sorts of tests are easy to see in animal studies. Aging rats were started on intermittent fasting regimens are markedly improved their scores of motor coordination and cognitive tests. Learning and memory scores also improved after IF. Interestingly, there was increased brain connectivity and new neuron growth from stem cells. This is believed to be mediated in part by BDNF (Brain Derived Neurotrophic Factor). In animal models, both exercise and fasting significantly increase BDNF expression in several parts of the brain. BDNF signaling also plays a role in appetite, activity, glucose metabolism and autonomic control of the cardiovascular and gastrointestinal systems.CRimprovesMemory

There are also very interesting mouse models of neuro-degenerative diseases. Mice maintained on IF, compared to normal mice, showed less age related deterioration of neurons and less symptoms in models of Alzheimers disease, Parksinon’s and Huntington’s disease.

In humans, the benefits to the brain can be found both during fasting and during caloric restriction (CR). During exercise and CR, there is increased synaptic and electrical activity in the brain. In a study of 50 normal elderly subjects, memory test improved significantly with a 3 months of CR (30% reduction in calories).Memory and Insulin

Neurogenesis is the process where neural stem cells differentiate into neurons that are able to grow and form synapses with other neurons. Both exercise and CR seem to increase neurogenesis via pathways including BDNF.

Even more interestingly, the level of fasting insulin seems to have a direct inverse correlation to memory as well. That is, the lower you are able to drive down fasting insulin, the more improvement on memory score that is seen.

Increased body fat (as measured by BMI) has also been linked to decline in mental abilities. Using detailed measurements of blood flow to the brain, researchers linked a higher BMI to decreased blood flow to those areas of the brain involved in attention, reasoning, and higher function.

Intermittent fasting provides one method of decreasing insulin, while also decreasing caloric intake.

Alzheimer’s disease (AD) is characterized by the abnormal accumulation of proteins. There are 2 main classes – amyloid plaques and neurofibrillary tangles (tau protein). The symptoms of AD correlate closely with the accumulation of these plaques and tangles. It is believed that these abnormal proteins destroy the synaptic connections in the memory and cognition areas of the brain.

Certain proteins (HSP-70) act to prevent damage and misfolding of the tau and amyloid proteins.  In mouse models, alternate daily fasting increased the levels of HSP-70. Autophagy removes these tau and amyloid protein when they are damaged beyond repair. This process, too, is stimulated by fasting.Dementia

There is substantial evidence that risk of AD is related to obesity. A recent population based twin study demonstrated that weight gain in middle age predisposes to AD.

Taken together, this suggests a fascinating possibility in the prevention of Alzheimer’s disease. Over 5 million American have AD and this number will likely increase rapidly due to the aging population. AD creates significant burdens upon families that are forced to care for their afflicted members.

Certainly fasting may have significant benefits in reducing weight, type 2 diabetes along with its complications – eye damage, kidney disease, nerve damage, heart attacks, strokes, cancer. However, the possibility also exists that it may prevent the development of Alzheimer’s disease as well.

The method of protection may also have to do with autophagy – a cellular self cleansing process that may help removed damaged proteins from the body and brain. Since AD may result from the abnormal accumulation of Tau protein or amyloid protein, fasting may provide a unique opportunity to rid the body of these abnormal proteins. We will cover autophagy next week.

2017-09-02T11:54:10+00:00 34 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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34 Comments on "Fasting and Brain Function – Fasting 24"

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Bryan
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I stopped eating breakfast when I was around 10 years old. I just figured out somehow that I felt better and had a better day if I skipped breakfast. Over the next 25 years, I earned a degree in electrical engineering, an MBA and co-founded a successful business. (I don’t mean to sound pompous, but I think my brain was functioning OK). However in my late 30s I succumbed to the clarion call from all dietitians, doctors, health groups and the media- ” It is the most important meal of the day! Your brain can’t function properly! Etc etc..) It… Read more »
Ermias Giovanni
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Cool story.
How low carb do you go as a general rule: are you keto?
Keep it up.

Marion
Guest

Funny, my daughter (now 14) hates breakfast and always goes to school without. Sometimes she won’t eat until 2pm when she comes home. She’s slim, athletic and bright as a button. I tried to force her to eat but she fought me all the way and I’m glad she did! So many of her peers are overweight to obese and she eats loads after her daily fast. Kids do it instinctively as long as we adults don’t interfere 🙂

Steve
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Greetings again Dr. Fung……another great article. At some point would you post your thoughts on fasting and kidney health. You mention other organs via your insert above. As a kidney Doctor I’m 100% sure you will advise that fasting is good for kidneys and CKD. Robb Wolf also posted a well-written article about Paleo and kidneys a couple years ago. The reason I ask is that some articles on fasting warn against doing if someone has diminished kidney function. In my last fasting/ LCHF period my kidney function improved from 40% to over 80%. That said I’d aprreciate your good… Read more »
John Caruso
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Yes, I am also very interested in Dr Fung’s view on people with impaired kidney function using both LCHF/Keto diets and fasting, especially extended fasting (10d+). I also encountered and ultimately ignored the warnings about LC diets stressing kidney due to “high protein.” After a kidney transplant (due to IgA nephropathy), I maintain a low carb diet, going full keto at times, and since July last year began occasional fasting. My kidney function increased from 40% post transplant, to over 60% after a couple years of low carb, to over 70% after a keto stint, to my highest of 78%… Read more »
John D
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I’d appreciate your thoughts on the application of fasting as a therapy for both major depression and for so-called post traumatic stress syndrome. I am quite certain that both are triggered by carbs although the mechanism has yet to be fully explained. Insulin resistance, microbiome issues, inflammation, presumably all engage together. Thus it seems lchf plus periodic fasting plus interval training = profound homeostasis, ie, return to evolutionary baseline, ie, health and happiness, our natural states. Really great to see you thinking outside of the obesity/diabetes issue; Mental health is certainly embedded in the obesity issue but it stands alone… Read more »
Cyan
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I’d like that too!

sten Bjorsell
Guest
Needless to say, another very inspiring article making the case for IF stronger! Looking forward to polish up my grey cells this way, always needed! This is a little off topic, regarding Type 1 diabetics. There is currently a discussion in Sweden in regard of danger of “euglycemic ketoacidosis” for DB-1 if they reduce carbohydrates (too much(?)). The argument against reducing carbs comes from a diabetic paper that (tragically) seems to defend substantial incomes from (overpriced) advertisements by insulin selling pharmaceutical companies, the way I see it. In the cases I have read about there has always been a combination… Read more »
Samuel
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I have been low carb – real food for about four years now. I was never over weight, and my motivation may be different from a lot of readers here. I went ketogenic (less than 50g carb per day) and confirmed it with blood serum ketone measurements for about 9 months. I went back to eating 40-80g per day just because it takes less meticulous accounting. I became interested in fasting after becoming aware of the two competing theories of cancer and reading about Thomas Seyfried’s work on the metabolic theory of cancer. I recently fasted for 72 hours and… Read more »
Lisa
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Samuel, thank you for sharing your experience. Please share more specifically about your fast. Was it water only, broth, herbal teas, etc.?

genevieve
Guest

did u ever get the answer to this? i would love to know

Wenchypoo
Guest

This blog post contains a chart of what optimal levels of BG, ketones, A-1C, and glucose/ketone ratios look like: http://optimisingnutrition.com/2016/02/22/optimising-blood-sugars-with-rd-dikeman/

Scroll down until you see the chart.

John C
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I certainly feel more alert after a fast – even one as short as 24 hours. In fact I rarely fast longer than 24 hours because I don’t feel safe driving with blood glucose levels below 4 mmol/l (72 mg/dl). I have recently concentrated on lowering my carb and protein to less than 50g each per day because of my poor kidney function and have found it easy to keep fasting for 24 hours two or three times a week. I believe that verybody has their own combination of ailments and dietary requirements and it’s important to note what effects… Read more »
Amberly
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I did my first extended fast last October and felt fabulous! More energy, clarity, etc. than I had had in ten years. I did keto the next week and then went away for a weekend with friends. I figured this was a “feasting” type of event, so had a fast food meal, and a half hour later, had a tonic clonic (grand mal) seizure. They took me to the ER. I have had two other tonic clonic seizures, both precipitated by stress, lack of sleep, and lack of food. (First was in college during finals after staying up all night… Read more »
Amberly
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I don’t know why this posted before I was done. See clarified post below.

BobM
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I had blood tests performed after a 4.5 day fast, and had fasting blood sugar at 63 mg/dL. I also had some whacked-out cholesterol numbers, relative to a test done a few months earlier. This week, I’m on a 5 day fast and had a blood test done for my cardiologist after about 12 hours of fasting. I’ve paid for a second blood test, which I’ll have after 4.5 days of fasting. I’ll report back after that. For me, on longer fasts (3+ days), I can have some mental acuity problems (I’ll have trouble concentrating, for instance), but these seem… Read more »
Amberly
Guest
I did my first extended fast last October and felt fabulous! More energy, clarity, etc. than I had had in ten years. I did keto the next week and then went away for a weekend with friends. I figured this was a “feasting” type of event, so had a fast food meal, and a half hour later, had a tonic clonic (grand mal) seizure. They took me to the ER. I have had two other tonic clonic seizures, both precipitated by stress, lack of sleep, and lack of food. (First was in college during finals after staying up all night… Read more »
BobM
Guest
Amberly, I believe that 7 day fasts are “faster” (in terms of insulin reduction, clearing fat from your pancreas and/or liver, etc.) than are short fasts. However, I find longer fasts to be more difficult, so I do these only every once in a while. For instance, this week, I’m doing a 5 day fast. This is my third 5-day fast since starting IF last March. For next week and a few weeks thereafter, I will do a fast from Sunday dinner to Tuesday dinner, then fast Friday until dinner. Note that I don’t eat breakfast anymore, so even on… Read more »
Amberly
Guest

@BobM thank you! Those are some really great things to think about. I hadn’t considered a protocol like that, so it gives me some ways I could mix it up on my own.

Danielle
Guest

Is headache “stress on the brain”?
Is it wrong to think there is a time of “switching fuels” from sugar to ketones in the brain? i.e. at that point in time when Alzheimer’s patients become lucid on ketones?

Lonnie
Guest

Hi Bob, I’m hearing you with the water coming out during a fast. After years of T2D UTIs and the like, it feels fantastic! The most enjoyable passing of fluid. I find this also happens when I enter/re-enter Ketosis.

Steve
Guest

Dr Fung and Megan…just received my two copies of the Obesity Code Book: one for me and one for local and supportive Korean MD. helping me. My quick scan during my break today suggest that the book was well worth the wait! Many thanks again for all you do!

Wenchypoo
Guest

I just got done devouring the book “The Everything Guide to Nootropics” by Evan Brand (Dr.? I’m not sure–he’s an NPT and CPT, and I don’t know what those initials stand for). After reading your article above, I wonder if it’s any use delving into the world of nootropics for brain improvement–it seems fasting does the same stuff (or almost the same stuff) as drugs/supplements, or even the brain-healthy food nutrients. Am I right?

Debra Griffith
Guest
I also would be interested in a post about kidney function and fasting/low carb. I just started on a drug called Topamax for chronic pain (one of 3 meds I take since 2 major back surgeries), which works fantastic, and of which a side effect is weight loss. However, there is a warning that it should be used with caution by people who are on a ketogenic diet because of the increased risk of kidney stones, which I have started to experience, and then after doing more research, have come to find numerous cases of kidney disease and failure being… Read more »
jcm baril
Guest
Sixteen pounds down since November 2015. Feels like an invisible little micro robot is going around to every cell in my body, with a pin, sticking it into each and every one and deflating them. As the old commercial for Alka-Seltzer use to sing: “Pop, pop, fizz, fizz, oh what a relief it is!!!” Have reduced portions; can’t eat as much as before. Have had to throw spoiled food out, as I did not get around to using it. Am now buying less food, saving a LOT of money! Pop! Pop! Fizz, fizz. Oh! what a RELIEF. IT. IS!!
cajunu
Guest

jcm, what is your fasting protocol – alternate days, multi-days, missing a meal? Do you have much to lose? Thanks in anticipation.

Deb Rayson
Guest

Hi. Could someone please tell me what they drink on a fast and is it OK to do it once a week? Thank you. Deb

Sarah
Guest
Hi Deb, I drink 1-2 cups of black coffee without sugar, plenty of water – 3litres or more (more than the non fasting days), a tbsp of apple cider vinegar in a cup of warm water with salt if I feel gassy in the morning and sometimes 1 cup of coffee with milk without sugar if I feel a headache starting. If the headache persists even after the coffee, I break the fast. Dr Fung says its fine to drink bone broth on fasting days and many people do that. For me that didn’t work as I start feeling extreme… Read more »
Danielle
Guest

Fizzy water with a slice of lime and sprinklings of sea salt. I know Dr Mosley does 6:1 (fasting 1 day) as weight maintenance. I believe you will get better results if you fast for a little longer.

Johnny
Guest

Hi Dr. Wong,

It was a blessing watching your youtube episode about reversing T2D. I am really motivated and encouraged to follow your regiment. Please let me how to start.

Thank you very much.

Regards,

Johnny

Johnny
Guest

Hi Dr. Fung,

It was a blessing watching your youtube episode about reversing T2D. I am really motivated and encouraged to follow your regiment. Please let me how to start.

Thank you very much.

Regards,

Johnny

Anderson
Guest

@ Johny-

You may start your program by joining IDM &instructions are very clear :

https://intensivedietarymanagement.com/join/

Marie
Guest
At some point would you post your thoughts on fasting and thyroid gland functions? I’m a woman, 43 years old, and my mother suffers from hypothyroidism. A couple of years ago I went through a small life crisis and also I felt tired, frozen, dropped a lot of hair, slept a lot, gained weight and I tried intermittent fasting 16/8 at the same time. I tested my TSH, T3 and T4 levels and they where not at all perfect. The doctor thought I might be on the verge of getting hypothyroidism just like my mother, but he wanted to do… Read more »
Anne
Guest

Hi Dr Fung, I am presently doing a 3 week fast in a wellness center in Germany.
I am thin and fit but suffer from Restless Legs Syndrome.
I saw a documentary about fasting last year where the benefits to Parkinson’s were mentioned and since the medication I take for my RLS is the same as for Parkinson’s I thought it is worth the try.
I started week 2 yesterday and feel good. They use the Buchinger method.
I would appreciate your advice.
Thank you

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