Researchers from the Johns Hopkins University School of Medicine and the National Institute on Aging at the National Institutes of Health have uncovered promising findings regarding the effects of intermittent fasting versus a standard healthy diet on brain health in older adults with obesity and insulin resistance. Cell metabolismfound that both diets led to improvements in cognitive function, with intermittent fasting showing a slightly stronger effect.
As people live longer, the prevalence of diseases such as Alzheimer’s disease and related dementias is expected to rise, posing major challenges for individuals, families, and healthcare systems. Cognitive decline not only impacts quality of life but also leads to increased disability and loss of independence, making effective prevention strategies urgently needed.
One of the key factors linked to brain aging and the development of Alzheimer’s disease is insulin resistance. Insulin resistance, which becomes more common with age and obesity, affects the body’s ability to regulate glucose and is associated with cognitive impairment and neurodegenerative diseases. Given this relationship, interventions that improve insulin sensitivity may mitigate cognitive decline and promote brain health in older adults.
“It is widely believed among scientists and the general public that diet in general, and intermittent fasting in particular, is beneficial for cognitive function and brain health, and may reduce the risk of Alzheimer’s disease. However, there is little data from clinical studies to support this idea. We sought to fill this evidence gap by comprehensively evaluating the effects of 5:2 intermittent fasting and a healthy diet on cognition and multiple brain health biomarkers,” said the study authors. Dimitrios Kapogiannisis a senior investigator and division chief of the Human Neurosciences Division at the National Institute on Aging.
Researchers recruited 40 older adults with obesity and insulin resistance — a group at high risk for developing brain aging and cognitive decline. These participants were randomly assigned to one of two eating plans: the 5:2 intermittent fasting diet or the USDA Certified Healthy Living diet.
The intermittent fasting group followed a diet that restricted their calorie intake to one-quarter of the daily recommended intake and consumed only two 480-calorie shakes per day for two consecutive days each week, while the healthy living group followed a daily healthy living diet that emphasized a balanced diet that included fruits, vegetables, whole grains, lean protein, and low-fat dairy products and limited added sugars, saturated fat, and sodium.
To monitor and enhance adherence to the dietary plan, participants were visited in person for anthropometric measurements and blood sampling at weeks 2, 4, and 6, and contacted by phone or email at weeks 1, 3, 5, and 7. The final visit was at week 8, with assessments conducted at the beginning and end of the study period.
Evaluations included brain health measures, cognitive tests, and whole-body and peripheral metabolic measurements. Neuron-derived extracellular vesicles were collected from participants’ blood and analyzed for biomarkers related to brain cell activity and insulin signaling. Additionally, brain imaging and cognitive performance tests were performed to measure the impact of the diet on brain aging and function.
The study results revealed that both intermittent fasting and a healthy diet led to improved insulin resistance and cognitive function. Both groups of participants experienced a decrease in insulin resistance, but the improvement was more pronounced in the intermittent fasting group. This was evidenced by a significant decrease in specific biomarkers of insulin resistance found in neuron-derived extracellular vesicles.
In terms of brain health, the study found that both diets helped slow the rate of brain aging, especially in areas of the brain important for executive function, such as the anterior cingulate cortex and prefrontal cortex. This was measured using brain age gap estimates from MRI scans. Brain age gap indicates how old or young an individual’s brain appears compared to their chronological age. Both diets reduced brain age gap similarly, suggesting a positive effect on brain aging.
“While both diets are good for overall health and brain health, 5:2 intermittent fasting showed stronger effects on reversing insulin resistance, improving executive function, and optimizing brain metabolism than the healthy living diet,” Kapogiannis told PsyPost. “However, we found no evidence that the two diets alter Alzheimer’s-related biomarkers in the short term. Finally, genetic factors such as gender and APOE may alter responses to the diets, so the choice of which diet is best for you should be an individual one.”
Specifically, the intermittent fasting group showed greater improvements in tasks related to strategic planning and cognitive flexibility. They also showed greater memory gains, especially in long-delay cued recall, compared to the healthy lifestyle group. The intermittent fasting group increased their physical activity levels and reduced their sedentary behavior, while the healthy lifestyle group showed no significant changes in physical activity.
Interestingly, despite the overall positive results, the study did not find any significant changes in cerebrospinal fluid biomarkers associated with Alzheimer’s disease, such as amyloid beta or tau protein, suggesting that while the diet had clear benefits on insulin resistance and cognitive function, it had limited impact on Alzheimer’s disease-specific biomarkers.
“Several things surprised us: the fact that a low-intensity, traditional intervention such as the Healthy Living diet was effective in improving brain health, and across many outcomes was nearly as effective as a high-intensity intervention such as 5:2 intermittent fasting,” Kapogiannis explained, “and the fact that we saw no improvement in cerebrospinal fluid biomarkers of Alzheimer’s disease; however, the intervention lasted only eight weeks, so it’s possible that a longer intervention period would have improved the biomarkers.”
Although the findings are promising, some limitations must be considered. The study period was relatively short, so the long-term effects of the diet remain unknown. Furthermore, the sample size was small, with only 20 participants in each diet group, making it difficult to draw clear conclusions about subgroups based on gender or genetic factors.
“We can speculate about the long-term effects of dietary interventions, but we can never really know,” Kapogiannis points out. “It’s essential to study intermittent fasting over a longer period of time, and we also need to combine dietary interventions with ketone supplements to see if there are additional benefits to boosting ketone levels in the brain. In the long term, I think an individual’s dietary choice should be guided by the following principles: Precision MedicineIt is classified based on gender, genetic factors and biomarkers.”
By employing a comprehensive and diverse approach to assess the impact of dietary intervention on brain health, this study establishes a methodological standard upon which future research can build. This study highlights the potential of neuron-derived extracellular vesicles, magnetic resonance imaging, and magnetic resonance spectroscopy to provide detailed insight into how diet affects cognitive function and insulin resistance in older adults.
“We hope this study will serve as a blueprint for future studies to rigorously evaluate the long-term effects of diet on brain health,” Kapogiannis said.
the study, “Brain responses to intermittent fasting and healthy eating in older adultsThe authors of “The Impact of Breast Cancer on Breast Cancer Patients in the Early Stage of Cancer Patients with Breast …
