Want More Brain Energy? Try This Diet, Which Could Prevent Alzheimer's, Too

What doesn't kill brain cells might make them stronger. The brain cells of mice who regularly fast may grow more than usual once they get food again, according to research presented at the Society for Neuroscience's annual meeting in November and first reported by New Scientist.

One particular protein may be behind the growth: brain-derived neurotrophic factor (BDNF). In humans, BDNF may be involved in learning and memory. Levels of this protein tend to decline as a person gets older, especially if someone is diagnosed with a disease that can affect cognitive functions like Alzheimer's. However, levels of this protein increase by up to 50 percent in mice that have been fasting.

"This makes sense in a lot of ways," Mark Mattson, one of the researchers at the National Institute on Aging, which is behind the research, told Newsweek. He looks at the results from an evolutionary perspective. Human ancestors, before we had continuous access to food, were similar to animals in the wild, which go extended periods of time without food, said Mattson. "It's normal for them to go a week without killing a prey and then they eat it all at once," he said. "They have to be able to function at a high level both mentally and physically." If a brain cell can survive between meals, it's likely to seize the next opportunity it has to get energy and grow.

In theory, Mattson said, BDNF might be stimulating cells to produce more mitochondria. Mitochondria are often described as the powerhouse of the cell—they're what are responsible for transforming chemicals into an energy form that a cell can use to function. Having more of these mitochondria may allow brain cells to make more connections to other brain cells, too.

For rodents, at least, intermittent fasting has been linked with decreasing cellular damage after strokes and increasing lifespans. However, mice are (obviously) not humans—there's a limit to what science can say about fasting's effect on the human brain. "There has been virtually nothing done—no published studies—looking at the effect of intermittent fasting on the brain," he said.

However, Mattson and his colleagues are working on changing that. A clinical trial to see how fasting might affect brain function in older women is ongoing. For that trial, people are asked to eat normally for five days and severely restrict their calories for two days—a diet often referred to as a 5:2 diet or a Fast Diet.

He also has some theories about how intermittent fasting might affect cancer. Perhaps, he said, fasting might force a person's body to run on something other than sugar for energy. Cancer cells, however, might not be able to run on that alternate fuel source, called ketones—potentially starving them out and making them more vulnerable to treatments. (There are plenty of clinical trials that are working on figuring out if this effect might be real, too.)

However, that's still speculation. For now, so is the idea that fasting might make your brain work better. What Mattson can say, though, is that it might—"if you're a mouse or a rat."