A pilot study of older women with overweight or obesity suggests that limiting meals to a nine-hour window and avoiding food for four hours before sleep may help preserve cognitive abilities. Researchers at Rutgers University in New Jersey found hints of improvement in mental skills among participants who ate within the restricted period compared with those who spread meals over a longer time.
Study details and findings
The small clinical trial involved 47 women aged 50 to 79, all living with overweight or obesity. All participants were encouraged to cut 500 calories from their daily diet for six months. Within the group, 26 women were advised to eat only within a nine-hour window, typically between 10am and 6pm, while the rest spread their meals over about 12 hours.
At the end of the trial, both groups lost a similar amount of weight—an average of about 7kg (15lbs). However, cognitive tests revealed that those who confined eating to the narrow window performed better on spatial planning and problem solving tests. There were also indications of fewer errors on memory and learning tests, though multitasking and reaction time tests showed no difference between the groups.
Potential benefits beyond weight loss
Prof Sue Shapses, a nutritional scientist at Rutgers University who led the study, noted that losing weight alone can help slow cognitive decline in older age, but there may be “additional benefits” for people who do not eat outside an eight to nine-hour window and stop eating four hours before going to sleep. She described the effects as “modest” but suggested that time-restricted eating may improve the ability to remember information for everyday tasks and reduce mistakes linked to memory, attention, and problem solving.
The findings were presented at Nutrition 2026, the annual meeting of the American Society for Nutrition in Maryland. The researchers plan to investigate why the timing of eating matters, potentially involving circadian rhythms, metabolism, and inflammation.
Broader context and expert commentary
Dementia is the leading cause of death in the UK and the seventh worldwide, causing nearly 2 million deaths globally each year. While some risk factors like age and genetics are unavoidable, experts estimate nearly half of cases could be prevented or delayed through lifestyle changes. Obesity in middle age can raise the risk of dementia by 30%.
Prof Wendy Hall, head of nutritional sciences at King’s College London, who was not involved in the study, said that time-restricted eating is a plausible approach to supporting cognitive health in midlife and older adults with overweight. “Not only because it may help with weight management but also because avoiding large meals late in the evening may improve blood sugar control, vascular function and inflammation,” she said. She cautioned that the findings are preliminary and that the full peer-reviewed study is needed to determine if the improvements are clinically meaningful.
