An older Black man wearing glasses and a blue shirt drinks a glass of water in his kitchenShare on Pinterest
Researchers suggest that time-restricted feeding could slow cognitive decline and help manage Alzheimer’s symptoms. Maskot/Getty Images
  • A recent study using mouse models have found that time-restricted feeding or intermittent fasting improved cognition and reduced Alzheimer’s pathology in the brain.
  • Intermittent fasting, or time-restricted feeding, involves restricting the energy intake to fixed periods and fasting outside these times.
  • Intermittent fasting has several health benefits, such as improved sleep, weight control, blood glucose regulation, cardiac function, and gut health.
  • Some studies have shown intermittent fasting may also have anti-aging and anticancer effects.

Time-restricted feeding could help reduce the risk of cognitive decline and benefit those with Alzheimer’s disease (AD), according to researchers from the University of California San Diego School of Medicine.

In a recent study using a mouse model of Alzheimer’s, scientists adjusted the feeding schedule of mice to one 6-hour window each day. The researchers noted the window is equivalent to 14 hours of fasting for humans.

They found that time-restricted feeding corrects the circadian disruptions of Alzheimer’s, improves memory, and reduces the accumulation of amyloid — a protein tied to dementia progression — in the brain.

If these cognitive improvements in mice can be replicated in humans, time-restricted feeding could help with symptom management among those with Alzheimer’s.

The findings were published October 3 in Cell Metabolism.

Dr. Percy Griffin, PhD, the director of scientific engagement at the Alzheimer’s Association, who not involved in the research, told Medical News Today:

“The authors noted that one limitation of the study was the model used. The mouse model only displayed amyloid deposition, which is one of the hallmarks of Alzheimer’s. The model did not display other hallmarks including tau tangle formation [which is another marker of dementia] or brain cell loss. While this is interesting work, we need more research in other models for confirmation.”

Circadian disruptions — altered sleep rhythms and difficulty falling or staying asleep — are a common feature of Alzheimer’s disease, often beginning early in the course of the disease.

Prior research suggests a two-way relationship between circadian disruptions and Alzheimer’s disease pathology. “There is an established bidirectional relationship between circadian rhythm dysfunction and neurodegeneration,” Griffin said.

“Changes in circadian rhythms lead to protein accumulation and other changes associated with neurodegeneration. Further, neurodegenerative changes lead to changes in circadian rhythms and dysfunction.”

For the study, the researchers used transgenic mice engineered to develop Alzheimer’s disease pathology and wild-type mice.

They randomly divided the mice into two groups: transgenic and wild-type mice. All the mice were used to 12 hours of light and 12 of darkness.

The transgenic Alzheimer’s disease mice exhibited sleep disruption and altered activity rhythms, being much more active during the dark phase than the wild-type mice.

One group had constant access to food, and the other had food available for only 6 hours during the 12-hour light phase each day.

Despite the difference in food availability, both groups consumed equivalent volumes of food and showed no significant differences in body weight.

As well as taking blood samples from the mice for analysis, the researchers tested their cognitive function using the novel object recognition test (NOR) and an eight-arm radial arm maze (RAM).

At the end of the experimental period, they euthanized the mice and analyzed their brains to assess changes in gene expression and the extent of amyloid deposition.

Time-restricted feeding decreased blood glucose (sugar) levels in all the mice in the recent study.

The controlled feeding window also resulted in modified gene expression in the mouse model of Alzheimer’s, reducing neuroinflammation and regulating the circadian clock.

After 3 months, the researchers assessed the impact of time-restricted feeding on behavior in the Alzheimer’s disease mice. They found different effects in males and females, with only females increasing total sleep. Both sexes showed improved sleep onset and reduced hyperactivity.

The Alzheimer’s disease mice on time-restricted feeding exhibited significantly reduced amyloid plaques compared with those on unlimited feeding. The researchers suggest that time-restricted feeding may reduce the amyloid deposition rate and increase the amyloid clearance rate.

The mice on time-restricted feeding also showed improved memory and cognitive function. Before time-restricted feeding, the Alzheimer’s disease mice performed worse than wild-type mice in the NOR and RAM tests.

Following time-restricted feeding, they improved on both tests, whereas the Alzheimer’s disease mice on unlimited food continued to show deficits.

For the Alzheimer’s disease mice on time-restricted feeding, cognitive performance improved to almost the levels of the wild-type mice.

Time-restricted feeding involves eating within a certain time period each day or fasting for one or more days a week while eating normally on other days.

Like intermittent fasting (IF), time-restricted feeding involves entirely or partially abstaining from eating for a period of time.

But unlike intermittent fasting, which may involve calorie restriction, time-restricted feeding typically allows you to consume as many calories as you like during an eating window.

Although research in humans is limited, many studies are currently in progress. Intermittent fasting has been associated with several health benefits, such as:

  • weight loss
  • reduced type 2 diabetes risk
  • improved heart health
  • reduced risk of some cancers
  • improved brain health

Previous mouse studies have linked time-restricted feeding with gene modification, longevity, and reduced cancer risk. The latest study found that time-restricted feeding corrected the circadian disruptions of Alzheimer’s disease in mice.

Sebnem Unluisler, a genetic engineer at the London Regenerative Institute, not involved in the study, explained the potential mechanisms behind the changes.

“Numerous processes may contribute to intermittent fasting’s beneficial effects on Alzheimer’s disease,” she told MNT.

“Autophagy, a cellular process that eliminates damaged components and has been associated with neuroprotection, may be one important mechanism. Intermittent fasting may improve autophagic functions, which could aid in the removal of harmful protein clumps like amyloid-beta, a sign of Alzheimer’s disease,” Unluisler added.

“Furthermore, by encouraging the release of brain-derived neurotrophic factor(BDNF), intermittent fasting may enhance brain function, lower oxidative stress, and enhance metabolic health,” she noted.

The researchers who conducted the study believe that time-restricted feeding could be an easy way to help alleviate circadian problems in people with Alzheimer’s disease, one of the main causes of them needing residential care.

“Time-restricted feeding is a strategy that people can easily and immediately integrate into their lives,” said senior study author Dr. Paula Desplats, professor in the Department of Neurosciences at UC San Diego School of Medicine.

“If we can reproduce our results in humans, this approach could be a simple way to dramatically improve the lives of people living with Alzheimer’s and those who care for them.”

Unluisler also commented on the potential to translate these findings from mice to humans:

“Even though the study was done on mice, and findings from animal studies can be difficult to translate to human studies, it provides a good basis for thinking about how intermittent fasting can affect Alzheimer’s disease in humans. Given the possible advantages of intermittent fasting on metabolic health and neuroprotection, it is logical to speculate that comparable effects would be seen in humans.”

However, Dr. Griffin urged caution: “The changes in Alzheimer’s and circadian rhythm dysfunction negatively impact each other, and more research is needed to firmly establish causality,” he said.

More work is needed — both in models and in people — before this approach can be recommended broadly as a strategy for reducing the risk of neurodegeneration,” Griffin concluded.

Alzheimer’s disease — a progressive and ultimately fatal neurodegenerative condition — is the most common form of dementia.

Current treatments, such as lifestyle modifications and medication, may help alleviate Alzheimer’s symptoms. Common symptoms may include:

  • memory loss
  • sleep issues
  • behavioral problems

Newer monoclonal antibody drugs — donanemab, aducanumab, and lecanemab — that clear amyloid plaques perform well in trials.

However, these drugs are not yet widely available, and research is ongoing.