People 70 and older who eat between 2,100 and 6,000 calories a day may be at double the risk of these deficits in memory, which can be an early sign of Alzheimer’s disease, the study authors said.
“Excessive daily caloric consumption may not be brain-health friendly,” said lead researcher Dr. Yonas Geda, an associate professor of neurology and psychiatry at the Mayo Clinic in Scottsdale, Ariz.
“It may sound like a cliche, but we need to be mindful of our daily caloric consumption,” he said. “The bottom line is that eating in moderation, not in excess amount, may be good for your brain.”
The results of the study are due to be presented in April at the annual meeting of the American Academy of Neurology, in New Orleans. The data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
For the study, investigators collected data on more than 1,200 people, aged 70 to 89, living in Olmsted County, Minn. Among these people, 163 had been diagnosed with the memory deficits known as “mild cognitive impairment.”
Each person told the researchers how much they ate. One-third ate between 600 and 1,525 calories a day, one-third between 1,526 and 2,142 calories a day, and one-third ate between 2,143 and 6,000 calories a day.
Among those who ate the most, the odds of being diagnosed with the impaired-memory disorder was more than twice that of those who ate the least, the researchers found.
There was no significant increase in risk for memory problems among those in the middle group, the researchers added.
These findings remained the same after taking into account a history of stroke, diabetes, education and other risk factors for memory loss.
“We also looked at BMI and obesity,” Geda said. BMI, or body mass index, is a measurement based on height and weight. “But there was no significant difference between the normal [participants] and mild cognitive impairment when it comes to these two variables,” he said.
Why overeating affects the brain isn’t clear, but “excessive caloric intake may lead to oxidative damage leading to structural changes in the brain,” Geda suggested.
Commenting on the study, Dr. Neelum Aggarwal, an associate professor of neurological sciences at Rush University in Chicago, said that “as the population of the U.S. is aging at a rapid rate, in addition to becoming increasingly obese, physicians are being asked by their elderly patients about their risk for various diseases, specifically cognitive [mental] decline and dementia.”
These findings allow doctors to start the discussion about the links between common healthy living practices — eating a nutritious diet, limiting sugar — to overall brain function, he said.
“This study furthers the discussion of what the possible mechanisms are for the development of cognitive decline and offers strategies for disease prevention through nutrition and caloric restriction,” Aggarwal said.
Another expert, David Loewenstein, a professor of psychiatry and behavioral sciences at the University of Miami Miller School of Medicine, said that “this makes a lot of sense because increased caloric intake is associated with obesity and metabolic syndrome, so it is not at all surprising that increased calories are associated with increased cognitive impairment.” Metabolic syndrome is a group of risk factors linked to heart disease and other health problems.
“This study suggests that anything that’s good for the heart — like decreased calories — is good for the brain,” Loewenstein added.
While the study found an association between overeating and memory impairment, it did not prove a cause-and-effect relationship.