- Past studies have shown that intermittent fasting and living a physically active lifestyle may be able to slow age-related cognitive decline, which is a natural part of aging.
- New research has found that exercise, particularly short bursts of high intensity exercise can increase the amount of neuroprotective brain-derived neurotrophic factor (BDNF) in the body.
- The study found that high intensity exercise is a more efficient way to increase the level of DBNF than fasting alone.
Aging is associated with lower levels of cognitive performance. Research has shown that cognitive ability is at its peak around the age of 30.
Common symptoms associated with age-related cognitive decline include:
- a slow down in reasoning and problem-solving skills
- decreased in verbal and numeric ability
- a decline in memory
Some level of cognitive decline is unavoidable, but research suggests access to sufficient nutrition and exercise can help keep the body but the mind healthy.
“There is a substantial amount of evidence demonstrating that exercise possesses a significant ability to reduce the risk of cognitive decline […] “preventative lifestyle medicine”, […] is more about percentage risk reduction, which is likely greater alongside more than one lifestyle change,” explained Ryan Glatt, senior brain health coach and director of the FitBrain Program at Pacific Neuroscience Institute in Santa Monica.
Intermittent fasting (IF) and exercise have both been shown to slow down age-related cognitive decline. However, different processes both encourage a “cerebral substrate switch,” which redirects the brain from using glucose as its primary fuel source.
Studies have shown IF reduces glucose levels and increases the number of circulating ketones which become the primary fuel source for the brain. Similarly, lactate produced by muscles during exercise has been shown to account for up to 25% of the brain’s fuel.
This switch in fuel has been linked to an increase in the levels of the neuroprotective protein — brain-derived neurotrophic factor (BDNF) — which is associated with brain health. BDNF plays an important role in cell survival and growth, impacting learning and memory function.
Lower levels of BDNF have been associated with a range of neurodegenerative diseases like Alzheimer’s and Parkinson’s disease.
Now, new research led by Dr. Kate N Thomas, senior lecturer at the University of Otago has found that even short bursts of high intensity exercise can increase the levels of BDNF.
The study is published in The Journal of Physiology
Comparing high and low intensity workouts
In a cross-over trial, the research team studied 12 fit and healthy participants, ages 18–56. Half of the participants were female, all had a BMI below 25, and all undertook regular physical activity.
People with chronic diseases and on daily medication were excluded from the trial.
The participants all underwent 4 different study regimes:
- a 20-hour fast
- 90-minute low intensity cycling calculated at 25% of the participant’s peak oxygen consumption
- 6-minute high intensity cycling calculated at 100% of the participant’s peak oxygen consumption
- a combination of exercise and fasting
Blood samples were taken throughout the trial at set time points to measure the amount of BDNF, glucose, insulin, and ketone body beta-hydroxybutyrate alongside platelet counts.
Fasting vs. HIIT
The research team found a 9-fold increase in ketone body availability after the 20-hour fast, but this was not linked to a notable change in BDNF levels.
In contrast, after 90 minutes of light cycling serum BDNF was raised by up to 14% regardless of whether the participant had fasted. The research team associated the raise with up to a 13% increase in blood platelets.
High-intensity cycling for 6 minutes increased the amount of circulating BDNF up to 5 times more than the longer sessions of low intensity cycling.
The increase was linked to a 6-fold increase in lactate levels, regardless of participant fasting. An increase in lactate level was not evident during low intensity exercise.
The research team also found that exercise increased the number of circulating platelets by 20%, to which they concluded, exercise has a greater impact on platelet count than fasting.
Is all exercise equal?
Medical News Today spoke to the study’s first author Travis Gibbons, about the importance of the type of exercise in this study.
He explained that “[…] any type of exercise is perfectly OK so long as the intensity can be high enough to produce some lactate. The intensity required to do that is relative to each individual.”
He went on the say that the participants in the study worked hard but not at their peak work rate. His simplest suggestion to anyone looking to achieve similar results was to “go all-out for 20-40 [seconds].”
“[P]eople have a pretty good sense of pacing and will pick an intensity they feel can be sustained for at least that period of time,” he noted.
What makes the study stand out
“I love seeing data that encourages people to live actively in the outdoors. The answer to a lot of modern-day (Westernized) health problems, is just beyond our doorstep. It is becoming more and more clear that simply getting up and moving outside throughout aging is a much simpler, effective, and equitable way to preserve ‘health,’ as opposed to searching for remedies to disease,” explained Gibbons.
Ryan Glatt, personal trainer and brain health coach for the Pacific Neuroscience Institute at Providence Saint John’s Health Center in Santa Monica, California, who was not involved in the study, echoed Gibbons.
“[M]ost individuals with cognitive decline or without, may not have the optimal ‘exercise prescription’ for their brain health, which is where an opportunity exists to fill that gap in clinical practice.”
— Ryan Glatt, brain health coach
“[…] this study, […] is interesting in furthering our understanding of how exercise variables, such as intensity and duration, in combination with dietary behaviors, may affect elements of brain health such as the expression of BDNF,” Glatt told MNT.
“The most interesting part about this study is the combined and separate arms of fasting and exercise, which is important as individuals are usually wondering what they can do in multiple areas of their lifestyle to improve brain health, not just one domain of lifestyle such as diet,” he continued.
“[I]t is pertinent that people develop lifestyles that prioritize brain health before neurodegeneration becomes symptomatic.”
— Travis Gibbons, study author
Limitations
The study is limited by its small sample size and lack of a control group.
“[T]his study creates more questions than it does answers due to its low statistical power and its multimodal study design,” commented Glatt.
The authors, however, argue that exercise is “an accessible, affordable, efficient, and equitable intervention” which can be included easily into daily life.
“Another question may be what the significance of BDNF expression is in the context of this study, as cognition or other aspects of brain function were not measured[…],” added Glatt.
He underscored that future research would need to focus on “how significant those benefits are, what sorts of benefits exist (cognitive, brain function or structure or mood), and how long those benefits may last.”
Can exercise and fasting protect the brain?
The next step for this work is to understand if combining exercise and fasting alters the neuroprotective effects.
“This will inform strategies more about the ideal ‘timing’ of exercise to achieve the best stimulus for brain-specific adaptations,” noted Gibbons.
The team is also interested in understanding how exercise affects the blood in the brain and is working on research that will allow them to sample blood from the brain during exercise.
“So far, we’re seeing that the blood in our brain is actually very different from that in the rest of our circulation,” said Gibbons.
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