Limiting the time you eat to a nine-hour window and avoiding eating four hours before bed could reduce the risk of dementia, a new clinical trial has suggested.

A pilot study looking at older women who were overweight or obese found that cognitive skills were improved for those who restricted the hours in which they ate compared with those that didn’t.

The findings were part of a weight-loss programme and suggest that it’s not just weight loss that can ward off age-related cognitive decline, but restricting the times in which you eat, Sue Shapses, professor of Rutgers University and the study’s principle investigator revealed.

“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 4 hours prior to going to sleep and reduce food intake to 8-9 hours per day, compared to the usual eating window of 12 hours per day,” she said.

Professor Shapses’ findings are set to be presented at NUTRITION 2026, the annual meeting of the American Society for Nutrition, outside Washington DC, on Monday.

The trial enrolled 47 women between the ages of 50 and 79 who were overweight or obese. All participants were counseled to reduce their calorie intake by 500 calories per day, and 26 were asked to restrict their eating to a window of less than nine hours per day, while the rest maintained a typical eating window of about 12 hours per day.

In the time-restricted eating group, participants generally ate only between 10am and 6pm, with an average daily eating window of 8.2 hours, compared to 12.3 hours per day on average among those asked to maintain the standard eating window.

After six months, participants lost about 15 lbs (6.8kg) on average across the groups. But those who consumed food within the eight and nine hour window, compared to those who maintained a 12-hour eating window, were better at spatial planning and problem-solving tests at the end of the weight-loss programme.

They also experienced fewer errors on memory and learning tests, but there was no significant difference in performance on multitasking or reaction time tests.

Professor Shapses explained: "There was a modest effect of time-restricted eating to improve spatial planning and problem-solving and on reducing errors related to memory and learning.

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

Further studies would be needed to confirm the findings as part of a larger group of participants, researchers said. They also hope to investigate why time-restricted eating might have these benefits, such as how it interacts with circadian rhythm, nutrient-sensing pathways, inflammation and metabolic health.

There are currently an estimated 982,000 people living with dementia in the UK, according to Alzheimer’s Society, a figure that is expected to rise to 1.4 million by 2040.