Six minutes of high-intensity exercise might prolong the lifespan of a healthy brain, perhaps delaying the start of Alzheimer's and Parkinson's diseases, a new, small study suggests.

Researchers found that short but intense cycling increased the production of a protein called brain-derived neurotrophic factor (BDNF), which is essential for brain formation, learning and memory. It's thought that BDNF might protect the brain from age-related mental decline.

"BDNF has shown great promise in animal models, but pharmaceutical interventions have thus far failed to safely harness the protective power of BDNF in humans," said lead study author Travis Gibbons, from the University of Otago in New Zealand.

"We saw the need to explore non-pharmacological approaches that can preserve the brain's capacity which humans can use to naturally increase BDNF to help with healthy aging," Gibbons said.

The report was published Jan. 11 in the Journal of Physiology.

BDNF promotes the brain's ability to form new connections and pathways, and also helps neurons survive. Animal studies have shown that increasing the availability of BDNF boosts cognitive performance, such as thinking, reasoning or remembering.

For this study, the researchers wanted to look at the influence of fasting and exercise on BDNF production in humans.

Working with a dozen men and women, the investigators compared fasting, low-intensity cycling for 90 minutes, six-minute high-intensity cycling, and a combination of fasting and exercise.

Brief but vigorous exercise was the most efficient way to increase BDNF compared to one day of fasting with or without lengthy, low-intensity exercise, the researchers said.

BDNF increased four to five times more compared to fasting, which showed no BDNF change, or prolonged activity, which showed a slight increase in BDNF.

More work is needed to better understand these findings, the study authors noted.

The researchers hypothesize that the brain switches its favored fuel source for another to meet the body's energy demands. This could mean metabolizing lactate instead of glucose during exercise, which potentially could initiate pathways that lead to more BDNF in the blood.

The BDNF boost could be due to an increased number of blood platelets, which store large amounts of BDNF. This is more heavily influenced by exercise than fasting, they explained.

Ongoing research will further study the effects of calorie restriction and exercise.

"We are now studying how fasting for longer durations, for example up to three days, influences BDNF," Gibbons said in a journal news release. "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."