A new twist on exercise, intermittent fasting, and BDNF

If you read Beating the Dementia Monster, you know research shows that exercise affects the progress of Alzheimer's disease, and it may even be able to prevent it.  (No one claims it cures it.)  The conventional thinking is that exercise prompts generation of a protein called the brain-derived neurotrophic factor, or BDNF.  BDNF has the ability to repair damaged brain cells and to prompt the formation of new neurons from stem cells.  

In 2018, we cited peer-reviewed research showing that about 400 minutes of exercise per week was optimal for impeding the progress of Alzheimer's disease, although the research said nothing about the relative intensity of the exercise.  (This led me to my current regimen of 55 minutes per day on the treadmill, six days per week.)  But the research never said how intense the exercise should be.  To get the results of the 2018 research, is walking around the block a few times enough, or must you run full speed the whole way? 

In 2020, we also cited research published in The New England Journal of Medicine stating that intermittent fasting would also encourage the generation of BDNF.  My review of what people were saying on the Internet (not a very scientific approach) found that the conventional wisdom was that a 20 hour/day fast would produce enough BDNF to be effective.  But is that true?  In any event, I've been following a 20 hour/day fast now for three years.  Some days it's more like 19 hours, but I only break the rhythm for special occasions.  (It's also hard to keep that schedule on Fridays, when Amy and I go out for lunch and do our shopping.)

My experience very definitely tells me that getting physical exercise has profoundly influenced the progress of my disease.  But I have no clue about whether the fasting has done anything.  I believe that I had largely "caught up" with normal aging by 2019 and wasn't expecting further improvement in 2020 when I began fasting.  And I have no control to compare to -- I have no twin who did the opposite of me that I can compare results with.  So who knows?  I keep fasting, because I don't want to rock the boat if it's working.

So there are two big questions: How hard to you have to exercise to get results, and does a 20 hour fast really affect the progress of neurodegenerative disease?  As it turns out, there is some interesting new research that tries to answer both questions.  However, it only tries to answer the questions from the standpoint of how much BDNF is generated.  As this article explains, intermittent fasting affects the brain in several ways other than through the production of BDNF.  Exercise, too, has positive effects beyond generation of BDNF.  Nevertheless, measuring what influences the generation of BDNF has a lot to say about how effective exercise and fasting are with respect to brain health.

I came across this research published in The Journal of Physiology that found 20 hours of fasting did little to increase the production of BDNF, but that six minute bursts of vigorous exercise did.  The six minute bursts were compared with 90 minutes of light exercise which did little.  The vigorous and light exercise were both bicycle riding.  Here's their press release.

Bear in mind that this was a small study involving only 12 subjects.  They were younger and not known to have any neurodegenerative disease.  Also, the research only measured production of BDNF.  It didn't measure the actual benefit to the brain from either fasting or different types of exercise.  Both fasting and exercise have important benefits to the brain beyond BDNF.

But I think it does tell us something helpful, particularly that the level of intensity of the exercise does seem to matter quite a bit.  I'm not planning to start doing 6 minute bursts of high intensity exercise, but the exercise I currently do is significantly more intense than the 90-minute bicycle ride they studied in the research.  It's 50 minutes on the treadmill at 3.5 mph at a 10-degree incline.  This is followed by a five minute cooldown at 2.5 mph with no incline.

All I can say is that, every morning when I wake up, I just can't believe it.  I remember back to 2015 when I was in free fall, and I thank the Good Lord for providing the wherewithal to battle this thing and hold it at bay.