Meanwhile, studies in animals dating back to the 1980s show caloric restriction can extend lifespan and slow aging. The current findings are “another piece of evidence that what we see in laboratory rodents on caloric restriction translates to humans,” said Richard Weindruch, PhD, of the University of Wisconsin–Madison, who has studied caloric restriction since 1975 but did not participate in Floel’s study. “I find it somewhat remarkable that such a brief period of [caloric restriction] actually would have these effects.”

Most studies in humans have looked at people who choose to sharply reduce their calorie intake long-term, he noted. This research has found clear signs of reduced cardiovascular disease risk, and perhaps slower aging, in these individuals. But this kind of lifestyle change isn’t easy and is best done with professional help, Dr. Weindruch added. “The whole trick here is to create a state of undernutrition without malnutrition, and it’s not a completely straightforward thing to do.”

Jeffrey Keller, PhD, a professor at Pennington Biomedical Research Center in Baton Rouge, La., who studies aging, metabolism, and neurodegeneration, agreed that seeing results after such a relatively short period of calorie restriction was surprising. It provides more evidence that what’s going on in the rest of the body, from inflammation to belly fat, can have major effects on the brain, he added. “It may very well be it’s the aging of the body that promotes the aging of the brain.”

Researchers who study caloric restriction have two main theories on how it might slow aging. One argument is that eating less slows down metabolism, so that the body produces fewer free radicals, which are byproducts of oxygen metabolism that can harm body tissues. Another is that reducing calorie intake keeps cells under a constant low level of stress, which makes them better able to cope with higher levels of stress when it comes along—similar to how the moderate stress induced by exercise can improve people’s health.

Floel said she and her colleagues are now planning larger studies of calorie restriction and mental function and will perform MRI brain scans on participants before and after they reduce their food intake in order to better understand what’s happening in the brain’s gray matter.

In the meantime, the findings offer yet another reason for people to try eating a little less, Floel added. “It’s probably a good idea anyway, and you might also do something for your brain.”

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