The greatest risk factor for Alzheimer's disease and dementia is aging, and research in aging biology suggests that caloric restriction (i.e., reducing caloric intake by 20–40 percent) may mitigate some of these risks. If caloric restriction can slow the body’s aging, there is a chance that it could delay age-related diseases such as Alzheimer’s.
So how can we reap the potential benefits of caloric restriction? It would be difficult for a healthy person to eat 20–40 percent fewer calories each day throughout life. But previous studies have found that intermittent fasting may have a similar effect.
Intermittent fasting, as the name implies, involves reduced calorie intake or full fasting for 16–24 hours, followed by regular eating. Preclinical studies in rodents suggest that long-term intermittent fasting might promote longevity, reduce cognitive deficits, improve cognition, and increase the generation of new brain cells.
While these studies are promising, no human clinical studies have confirmed that intermittent fasting or even standard calorie restriction promotes brain health or prevents dementia. Preliminary observational evidence and a small randomized controlled trial have suggested some protection from diabetes and cardiovascular disease, two age-related diseases often associated with an increased risk of dementia. And other studies are underway on specific types of intermittent fasting. The Fasting Mimicking Diet was developed by Dr. Valter Longo and involves eating a reduced number of calories on five consecutive fasting days each month in the form of a proprietary solution of micronutrients. And the 5:2 fast diet, now in clinical trials, involves reducing caloric intake to only 500–600 calories, two days per week. None of these studies are focused on dementia prevention or brain health.
Experts in aging biology and genetics do caution that intermittent fasting may be unsafe for certain people, including those with a very low BMI or diabetics receiving insulin or insulin-like drugs. And elderly people are at a greater risk for malnutrition, which research shows may exacerbate frailty, itself a risk factor for dementia. Therefore, reducing caloric intake or fasting may not be advisable for the elderly.
It is still unclear if intermittent fasting or even standard calorie restriction can prevent cognitive decline or dementia in healthy people. But, rates of obesity and diabetes are increasingly common and both are risk factors for dementia. Therefore, certain populations would likely benefit from reducing caloric intake or perhaps periodic fasting.
Nick McKeehan is a member of the ADDF's Aging and Alzheimer's Prevention program. He evaluates the scientific evidence for and against therapies to promote brain health and/or prevent Alzheimer's disease at our website CognitiveVitality.org and contributes regularly to the site's blog. Mr. McKeehan previously served as Chief Intern at Mid Atlantic Bio Angels (MABA) and was a research technician at Albert Einstein College of Medicine investigating repair capabilities of the brain. Mr. McKeehan received a bachelor of science degree in biology from Purdue University, where he was awarded a Howard Hughes Scholarship. He also writes about the biotechnology industry for 1st Pitch Life Science.
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