Time-restricted diets may cut dementia risk in older women, pilot study finds

Clinical findings from a small-scale pilot study propose that it may be possible to reduce dementia risk by restricting their eating to within fewer hours of the day. Overweight or obese older women who limited their daily eating window instead of just reducing their calorie intake displayed modest cognitive improvements in the study while participating in a weight loss program. 

“Losing weight alone will ward off some of the aging-related cognitive decline, and these data suggest that there may be additional benefits if you stop eating four hours prior to going to sleep and reduce food intake to eight to nine hours per day, compared to the usual eating window of 12 hours per day,” says Sue Shapses, Ph.D., the study’s principal investigator. She is a registered dietician and professor at Rutgers University and Rutgers-RWJ Medical Center, US.

The study authors are presenting their findings at the ongoing Nutrition 2026 conference (Jul 25–28), the first annual meeting of the American Society for Nutrition, alongside other premier dietary research.

Dietary interventions to long-term brain health

The researchers stress that Alzheimer’s disease and other forms of dementia have become more common as populations age — adding that women and overweight or obese individuals are at higher risk of developing these conditions.

Diet and various other lifestyle factors have been associated with dementia risk, they add. However, few studies have evaluated whether modifying these factors can reduce that risk.

The trial enrolled 47 women aged 50–79 who were overweight or obese. All participants were instructed to reduce their calorie intake by 500 calories per day. Twenty-six participants restricted their eating to a window of less than nine hours per day, while the rest maintained a standard eating time frame of around 12 hours per day.

Women in the study whose eating was confined to a smaller eating window tended to make fewer errors on memory and learning tests.Participants in the time-restricted eating group ate only between 10 a.m. and 6 p.m., with an average daily eating window of 8.2 hours, compared to 12.3 hours per day on average among those who maintained the standard eating window.

After six months of following this protocol, participants in both groups had lost the same amount of weight, or 15 pounds, on average.

However, compared to study participants who maintained a 12-hour eating window, those who consumed food for only eight to nine hours per day had significant improvements on spatial planning and problem-solving tests at the end of the weight-loss program.

Those whose eating was confined to a smaller window also tended to make fewer errors on memory and learning tests. However, the researchers found no significant difference in performance on multitasking or reaction time tests.

“There was a modest effect of time-restricted eating to improve spatial planning and problem-solving and reduce errors related to memory and learning,” says Shapses.

“These outcomes suggest a better ability to remember information during everyday tasks and reduce mistakes related to memory, attention, and problem-solving. Reductions in the eating window predicted greater improvements.”

Mixed results around time-restricted eating

The researchers add that future studies are needed to confirm the findings in a larger group of participants. They plan to evaluate whether these mechanisms might explain the possible benefits of time-restricted eating, such as the interactions between circadian rhythm, nutrient-sensing pathways, inflammation, and metabolic health.

Scientific consensus on the benefits of fasting is varied, as one study this year argued that intermittent fasting is unlikely to lead to weight loss in obese and overweight adults.

Researchers of that paper compared people using intermittent fasting to others who followed traditional dietary advice and those who made no changes to their existing lifestyle. The time-restricted protocol did not appear to have a clinical effect on weight loss in any of these cases, which multiple experts contested.

Another review of 71 global studies on food intake and cognition showed that adults going without food for between about eight and 24 hours have no meaningful difference in mental performance.

In contrast, a paper in The BMJ revealed intermittent fasting may outperform conventional calorie-restricted weight loss diets. However, researchers have also cautioned that without changing a person’s caloric intake, intermittent fasting does not lead to measurable improvements in metabolism or cardiovascular health.