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episode #231

New Study: 20 Hour Fast vs. Exercise for Learning and Memory!

March 6, 2023 in Podcast


This week I discuss a January 2023 study comparing fasting, 90 minute light exercise and high intensity exercise when it comes to upregulating brain-derived neurotrophic factor (BDNF), a protein involved in neuroplasticity, learning and memory, and may underlie some of these neuroprotective effects. Here are the results:

  • Fasting for 20 hours caused a 9-fold increase in ketone body delivery to the brain but had no effect on any metric of BDNF in peripheral circulation at rest.
  • Prolonged (90 min) light cycling exercise increased plasma- and serum-derived BDNF irrespective of being fed or fasted about 6-8%
  • Six minutes of high-intensity cycling intervals increased every metric of circulating BDNF by 4 to 5 times more than prolonged low-intensity cycling; the increase in plasma-derived BDNF was correlated with a 6-fold increase in circulating lactate irrespective of feeding or fasting.
Conclusion: Compared to 1 day of fasting with or without prolonged light exercise, high-intensity exercise is a much more efficient means to increase BDNF in circulation. So go out there and do some high intensity exercise either on a bike, sprinting, rowing, and/or swimming!

Have a great day!

Link to BDNF Study:


Brian (1s):

Hello and welcome to the Get Lean and Eat Clean podcast. My name is Brian grn. I'm a certified health coach, trainer and author, and this podcast is for middle-aged men and women looking to optimize their health and get their bodies back to what it once was 10 to 15 years ago. I will give you simple, actionable items to get long-term sustainable results. Thanks for listening and enjoy the show. All right, welcome to the getline e Klean podcast. My name is Brian Grn. I hope you had a great weekend and hope you listened to my interview with Dr. John jws. This is the third time I've had him on, he's the inventor of the X three bar, and we talked all about, you know, variable resistance versus weight training advantages of the X three bar building muscle as we age.

Brian (53s):

We got into his daily diet and much more. So Dr. Jws is an outspoken individual, but I enjoyed having him on for the third time. And, you know, the X three bar's been something that I've implemented into my workout routine along with a lot of my clients. So really enjoyed that interview. Check it out, episode two 30. Now, today I wanna get into a new study that came out January, 2023. I really enjoy going into some of these, these studies and just giving you a, a sort of a brief overview and a conclusion of it and what it, what it sort of means to you and how we can sort of apply it to our lives. Now, this one recently compared intermittent fasting for 20 hours to two forms of exercise, one of LI one light exercise and one like high intensity exercise and how it can increase or not do anything to what's called circulating bdnf.

Brian (1m 51s):

Now you're probably thinking, well, what is bdnf? BDNF is brain derived neurotrophic factor. It's a protein involved in neuroplasticity learning and memory and may underlie some neuroprotective effects on your brain. So it's one of those things that can decrease as we get older. And it's important to, you know, to just keep in the back of your mind. There's been, you know, some studies showing that people with Alzheimer's and dementia may have severely low B, D, and F. And so essentially it's for brain function and maintaining health of your brain cells. So it is important. And so it's been long known that fasting can help increase B, D, and F.

Brian (2m 35s):

Now this study might show something a little bit different, and I'm gonna go through that right now. And so essentially what it did is it took an individual's 11 individuals, so not a huge sample size, but it compared three different things. One, a 20 hour fast, two, a 90 minute light exercise, and three high intensity exercise. And compared, compared the BDNF in 12 human volunteers. And essentially what it did is it showed that fasting for 20 hours decreased glucose and increased ketones, which we all know, but had no effect on bdnf, which was fairly interesting that fasting for 20 hours had no effect on BDNF light cycling at 25% of peak oxygen uptake, which is like a light jog on your bike.

Brian (3m 25s):

So they did light cycling for 90 minutes and that increased serum b d F by six to 8% and that was independent of being fed or fasted. And third, it took the individuals and ran them through six 42nd intervals of at a hundred percent of V2 max peak. So that's pretty high intensity exercise right there. 40 seconds intervals is quite a long time. And that increased plasma and serum B D F as well as the b d F per platelet ratio, a four to five fold more than light exercise did.

Brian (4m 6s):

So the conclusions on this, which was fairly interesting and, and you know, one of those things where you know, you don't know until you try and, you know, this is not the end all study, it was done, it was done on a small sample size, but it just showed that, you know, 20 hours of fasting did not increase BDNF while high intensity exercise did and four to five times more than the low intensity cycling did. So I guess the conclusion is if you wanna maybe help with your brain health a little bit and you're thinking, which one should I do? Perhaps instead of, you know, going, doing a 20 hour fast or doing just a light cycling for 90 minutes, do six minutes of high intensity cycling intervals and in, in, at least in, in this small study, b d f increase four to five times more than the prolonged low intensity cycling or compared to almost one day of fasting.

Brian (5m 7s):

So I'll quickly share my screen here so you can see the study if you wanna just research it a little bit more, and I'll do that right there. And there it is. So that's the conclusion of the study. Hopefully this helps. And obviously this is just a small sample size, but it's showing you that if, if you wanna maybe help increase brain health a little bit with, with increasing BDNF circulating in your, in your, in your body, then you should do some high intensity exercise. And you could do this on a bike. You could do this in a pool. Okay? You can also do this on a treadmill, but whatever, whatever's most probably advantageous for you, I think some people get, get intimidated by maybe sprinting.

Brian (5m 50s):

You don't have to do sprinting in this example, it was done on a bike or you could do it on a row machine. So yeah, so give that a try. Let me know if you have any questions and I'd love it if you, if you enjoying these episodes, like and share. And I, I would love a review. That'd be great. So I appreciate you listening and I will talk to you on Friday with another great interview. Thanks so much for listening and have a great day. Thanks for listening to the Get Lean ean podcast. I understand there are millions of other podcasts out there and you've chosen to listen to mine and I appreciate that. Check out the show notes@briangrin.com for everything that was mentioned in this episode.

Brian (6m 33s):

Feel free to subscribe to the podcast and share it with a friend or family member that's looking to get their body back to what it once was. Thanks again and have a great day.

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