Older women who kept eating to a nine-hour window and avoided food for four hours before bed did better on some mental tests than women who spread meals across about 12 hours, in a small pilot study presented at Nutrition 2026 in Maryland. The finding adds to a growing case that when people eat may matter for the brain, not just what they eat.
The trial followed 47 women, aged 50 to 79, all living with overweight or obesity, for six months. Twenty-six were told to eat only between about 10am and 6pm, while the others were encouraged to spread meals and snacks over a longer day and both groups were asked to cut 500 calories from their daily intake. By the end, both groups had lost about 7kg on average, which is why the better test scores in the narrow-window group stand out: the difference was not explained by more weight loss.
On the tests, the nine-hour group performed better on spatial planning and problem solving. There were also hints that they made fewer errors on memory and learning tasks. On multitasking and reaction time, the two groups were the same. Sue Shapses, who led the study, said the effects were modest, but she said they point to additional benefits from restricting when food is eaten.
That matters because the research was aimed at a question with real public health weight. Dementia is the leading cause of death in the UK and is seventh worldwide, and previous work has suggested that nearly half of cases could be prevented or delayed through lifestyle changes. Obesity in middle age can raise the risk of dementia later in life by 30%, and many people in the UK and US eat over a 14-hour period, leaving only 10 hours overnight without food. In January, a review linked finishing eating before 7pm with better body weight, BMI, waist circumference, blood pressure and markers of metabolic health, but this new trial tries to push the idea a step further by looking at mental performance, not just weight or metabolism.
The friction is simple: both groups lost the same amount of weight, yet only the narrower eating window showed better performance on some cognitive tests. That leaves open whether the benefit comes from circadian timing, metabolic changes, reduced inflammation or some mix of all three, and the study does not show which mechanism matters most. Hall called time-restricted eating a plausible approach to supporting cognitive health in midlife and older adults with overweight, but the work is still preliminary and needs larger trials before anyone can say the pattern holds beyond this small group of women. For now, the most useful next step is obvious: find out whether the timing effect survives when the sample gets bigger, the test gets longer and the question moves beyond older women with overweight or obesity.
