Restricted eating hours may reduce cognitive decline in older age, researchers find

Limiting your eating and drinking to a specific number of hours each day, and stopping for at least four hours before you go to bed, might help protect the brain from decline as people get older, scientists suggest.

A small initial study looked at older women who were overweight. It found some signs that those who ate their meals within a shorter, specific period performed better on tests of mental skills compared to women who ate over a much longer part of the day.

These results are early because the study was small. However, if more research confirms these findings, it could mean that people can help maintain their thinking abilities by eating within a limited timeframe and not eating late at night.

Losing weight can help slow down cognitive decline in older adults, according to Professor Sue Shapses, a nutritional scientist at Rutgers University in the US. She believes there might be extra advantages for people who finish eating within an eight to nine-hour window and stop eating four hours before sleeping.

Dementia is a major cause of death globally. While some factors contributing to dementia cannot be changed, like age and genes, experts think that almost half of all cases could be prevented or delayed by making lifestyle changes. Being overweight in middle age has been shown to increase the risk of dementia later in life by 30%.

Professor Shapses led a small trial involving 47 women, aged between 50 and 79, who were overweight. For six months, they were asked to reduce their daily calorie intake by 500. Out of this group, 26 women were advised to eat only within a nine-hour period. For most, this meant eating between 10am and 6pm. The remaining participants ate their meals spread over about 12 hours.

By the end of the study, both groups lost a similar amount of weight, around 7kg (15lbs) on average. However, cognitive tests showed that the women who restricted their eating to the narrower nine-hour window performed better on tests measuring spatial planning and problem-solving skills. There were also indications that they made fewer mistakes in memory and learning tests, although performance on some tests of multitasking and reaction speed was the same for both groups.

Professor Shapses described the observed effects as modest. Nevertheless, she suggested that eating within a restricted time frame might enhance people's capacity to recall information for daily tasks and reduce errors related to memory, attention, and problem-solving. These findings were presented at Nutrition 2026, an annual meeting of the American Society for Nutrition in Maryland.

The researchers are now planning to explore the reasons behind these potential benefits, considering not just what we eat but also when we eat. They believe the positive effects could result from a complicated interaction between the body's internal clock (circadian rhythms), metabolism, and inflammation.

In many countries, including the UK and US, people commonly eat over a 14-hour period, leaving only 10 hours overnight without food. However, research indicates clear health advantages from extending the overnight fasting period. A review from January highlighted that finishing meals before 7pm was linked to significant improvements in body weight, BMI, waist size, blood pressure, and markers of metabolic health.

Professor Wendy Hall, who leads nutritional sciences at King's College London and was not part of this study, commented that limiting mealtimes to a short window could indeed benefit the brain. She explained that time-restricted eating is a reasonable approach for supporting brain health in middle-aged and older adults who are overweight. This is not only because it may assist with weight control but also because avoiding large meals late at night could improve blood sugar regulation, vascular function, and reduce inflammation.

Professor Hall advised that these results are preliminary. She stressed the importance of seeing the full, peer-reviewed study to determine if the observed improvements are significant enough to be considered clinically meaningful in medical terms.