A study from Johns Hopkins University School of Medicine and the National Institute on Aging at the National Institutes of Health (NIH) tracked 40 older adults with obesity and insulin resistance who were randomly assigned to either an intermittent fasting diet or a standard healthy eating plan approved by the U.S. Department of Agriculture (USDA). The study explored the potential benefits of both diets for brain health and provided important clues.
Insulin resistance, a hallmark of type 2 diabetes, is common in obese people. Studies have shown that people with insulin resistance are at higher risk for Alzheimer's disease and other cognitive impairments than healthy people. Therefore, various weight loss programs are often considered effective ways to reduce the risk of these metabolic and brain diseases.
Studies at Johns Hopkins University in animal models of diabetes and Alzheimer's disease have shown that intermittent fasting can improve cognition and insulin sensitivity. New research published in the journal Cell Metabolism on June 19 tested the effects of intermittent fasting on women and men at risk for cognitive impairment, and the authors note that the study provides a "blueprint" for using a wide range of biomarkers to assess the effects of diet, including analysis of extracellular vesicles - tiny packets of material shed by neurons (a type of brain cell that sends messages). Extracellular vesicles produced by these neurons are shed into the circulating blood, and in the new study, extracellular vesicles were collected during an eight-week period while participants were on one of two diets.
"The results suggest that both eating plans have benefits for reducing insulin resistance and improving cognition," said Mark Mattson, PhD, adjunct professor of neuroscience at the Johns Hopkins University School of Medicine and former director of the Laboratory of Neuroscience at the National Institute on Aging in Baltimore. "Both diets improved memory and executive function, but the improvements were more pronounced with the intermittent fasting diet. Other scientists may want to incorporate the brain markers (that we used) into additional, larger studies of diet and brain health."
Because people with obesity and insulin resistance may be more susceptible to cognitive impairment and Alzheimer's disease than those with normal metabolism and body mass index (BMI), Dimitrios Kapogiannis, MD, head of the Human Neuroscience Section at the National Institute on Aging and adjunct associate professor of neurology at the Johns Hopkins University School of Medicine, developed a method to isolate neuron-derived extracellular vesicles from blood. His lab has found molecular evidence of insulin resistance in extracellular vesicles shed by neurons in patients with diabetes and Alzheimer's disease, and blood samples are considered a good candidate for widespread use because they are relatively easy to collect.
To test the effects of the two diets on biomarkers of brain function, the new study recruited participants between June 2015 and December 2022 and completed four face-to-face assessments at facilities managed by the National Institute on Aging at MedStar Harbor Hospital in Baltimore. 40 of the participants completed the eight-week study. Of these, 20 were assigned to the intermittent fasting diet group, which restricted calories to a quarter of the recommended daily intake for two consecutive days each week, and followed the USDA's healthy living diet standards for the remaining five days, including fruits, vegetables, whole grains, lean meats, low-fat dairy products, and limited added sugars, saturated fats, and sodium. The remaining 20 were assigned to the USDA's standard healthy living diet group, which gave a standard eating plan every day of the week.
The average age of the participants in both groups was 63 years old, 25 were white, 14 were black, and 1 was Hispanic. Among them, 24 were men and 16 were women. All had obesity and insulin resistance.
The researchers found that both diets had the same positive effects on reducing markers of insulin resistance in extracellular vesicles, improving brain age (the biological age of the brain measured using MRI structural data), and reducing glucose concentrations in the brain. The reduced glucose concentrations are a natural consequence of improved glucose utilization.
Both diets also improved conventional measures of metabolic health, including weight, body mass index, waist circumference, blood fats (such as cholesterol), and insulin resistance.
Compared with the healthy living diet group, the intermittent fasting group showed about 20% improvement in executive function and memory (a set of mental skills that help plan and achieve goals). A few study participants reported mild side effects, including constipation, loose stools, and occasional headaches.
The researchers also found that levels of neurofilament (a structural protein in neurons) were increased in both diets, but mainly in the intermittent fasting group. What does this mean for brain health? The answer is unclear.
"This marker needs to be evaluated in further studies," said Dr. Mattson. "Neurons release a lot of proteins, and one idea is that intermittent fasting may induce some kind of neuroplasticity (structural changes) in neurons that leads to the release of neurofilament proteins."
The researchers cautioned that "people interested in intermittent fasting should plan carefully with a health professional, as it may be harmful to some people, including those with type 1 diabetes and eating disorders."
Awards, Support, and Collaborators
The research reported in Cell Metabolism was supported by the National Institute on Aging of the National Institutes of Health (ZIAAG000966, ZIAAG000975).
Other researchers who contributed to the study include: Apostolos Manolopoulos, Francheska Delgado-Peraza, Maja Mustapic, Carlos Nogueras-Ortiz, Pamela Yao, Krishna Pucha, Janet Brooks, Qinghua Chen, Lisa Hartnell, Mark Cookson and Josephine Egan from the National Institute on Aging, Roger Mullins from Morgan State University, Konstantinos Avgerinos from Wayne State University, Shalaila Haas and Sophia Frangou from the Mount Sinai School of Medicine and Ruiyang Ge from the University of British Columbia.
This article was independently created and published by Herbfields.net.