February 8, 2023
Just six minutes of high-intensity exercise may be good for the brain, according to a new report. The study found that short bursts of aerobic exercise raised levels of a protein that is known to protect and nurture nerve cells and connections in the brain. Longer periods of more leisurely exercise did not produce the same effects.
This preliminary study was small, involving only a dozen fit men and women aged 18 to 56. It found that those who cycled intensively for six one-minute periods, interspersed with periods of rest, had higher levels of circulating BDNF (or brain-derived neurotrophic factor), a protein that some researchers refer to as “Miracle-Gro for the brain” because of its ability to keep neurons healthy and even, in some instances, to foster the growth of new brain cells.
BDNF is a naturally-produced brain protein, and it belongs to a family of proteins called growth factors that help neurons to grow and remain healthy. It also strengthens pathways and connections between brain cells, allowing the brain to function better.
Exercise is known to raise levels of BDNF. In animal studies, BDNF has been shown to promote the formation and storage of new memories, enhance learning and boost overall cognitive abilities. Low levels of BDNF are associated with memory issues in animal studies, and with both memory and thinking problems in people.
For this new study, published in The Journal of Physiology, researchers at the University of Otago in New Zealand had the healthy volunteers come to their exercise lab for testing on multiple days. During some study sessions, the volunteers rode a stationary bicycle at an easy pace for 90 minutes. During others, they rode the bike at high-intensity for a minute, followed by a brief period of rest, and repeated the high-intensity cycle five more times.
During these sessions, the scientists took measurements of BDNF levels circulating in their blood before and after they exercised. Because fasting has also been shown to affect levels of BDNF, the researchers also had the participants not eat for 20 hours at different points during the study, to assess how intermittent fasting might alter the results.
The researchers found that the high-intensity bursts of exercise had by far the biggest impact on BDNF levels. Low-intensity exercise boosted BDNF levels only slightly, while the 20-hour fast did not have an impact on the volunteers’ BDNF levels.
“We found that the brief, intense exercise was the most efficient means to increase BDNF in the blood, and it did so by four- to five-fold, compared with only a slight increase with low-intensity exercise, and no change with fasting,” said the lead investigator, Travis Gibbons.
The findings do not prove that high-intensity “wards off dementia” or Alzheimer’s disease, Dr. Gibbons said. But “BDNF has shown great promise in animal models,” and high-intensity exercise could potentially be a way that “humans can use to naturally increase BDNF to help with healthy aging,” he said.
“We are now studying how fasting for longer durations, for example up to three days, influences BDNF,” the study author added. “We are curious whether exercising hard at the start of a fast accelerates the beneficial effects of fasting. Fasting and exercise are rarely studied together. We think fasting and exercise can be used in conjunction to optimize BDNF production in the human brain.”
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Travis D. Gibbons, James D. Cotter, Philip N. Ainslie, et al: “Fasting for 20 hours does not affect exercise-induced increases in circulating BDNF in humans.” The Journal of Physiology, January 11, 2023