Older women who squeezed all their meals into under 9 hours a day scored better on spatial planning and problem-solving tests after six months than women who ate across a normal 12-hour day, according to a small pilot trial presented July 26 at NUTRITION 2026, the American Society for Nutrition’s annual meeting in National Harbor, Maryland. Both groups cut 500 calories a day and lost roughly the same weight, which is why the researchers think the timing itself may have added something.
The trial was led by Sue Shapses, PhD, RD, a professor at Rutgers University. It has not been published in a journal, and the abstract did not go through peer review.
Key takeaways
- 47 women aged 50 to 79 with overweight or obesity, randomized for six months; 26 ate within under 9 hours a day, the rest kept a 12-hour window.
- Both groups lost about 15 pounds. Only the short-window group improved significantly on spatial planning and problem-solving.
- No significant difference on multitasking or reaction time, and no dementia, brain imaging, or blood biomarker outcomes were measured.
What the study found
All 47 women were counseled to cut 500 calories a day. The 26 assigned to time-restricted eating were told to keep their window under 9 hours, typically 10 a.m. to 6 p.m., and averaged 8.2 hours. The comparison group averaged 12.3 hours.
After six months, according to the American Society for Nutrition release, “participants had lost about 15 pounds, on average, which was about the same in both groups.” Coverage of the abstract put the split at roughly 7.5 kg in the time-restricted group and 6.1 kg with calorie cutting alone.
On testing, the release states that the women eating within 8 to 9 hours a day “had significant improvements on spatial planning and problem-solving tests at the end of the weight-loss program.” Significant here means the gain was large enough to be unlikely to come from chance alone. They also trended toward fewer errors on memory and learning tests, but that did not reach significance, so it could be noise. There was no significant difference on multitasking or reaction time.
“There was a modest effect of time-restricted eating on improving spatial planning and problem-solving and reducing errors related to memory and learning,” Shapses said.
Dr. Kumar’s take
Some outlets are already running this as time-restricted eating lowering dementia risk. This trial did not measure dementia. No amyloid, no tau, no neurofilament light, no brain imaging. It measured a battery of cognitive tests in 47 women over six months, and one domain out of several moved. I operate on brains, and a test-score change over half a year is not the same thing as a change in the trajectory toward dementia.
The second problem is the weight. The whole argument for meal timing rests on both groups losing the same amount, so anything left over must come from the clock. But the time-restricted group appears to have lost about 1.4 kg more. That gap was not statistically different, which in a trial this small tells you little: 47 people cannot reliably detect a difference that size. The cognitive gain may be riding on the extra pounds lost, not the clock.
Third, testing spatial planning, problem-solving, memory, learning, multitasking, and reaction time gives you several chances at a positive result. One hitting significance while the rest do not is what you would expect from chance alone. It is also what a real but narrow effect looks like. A 47-person pilot cannot tell you which.
That does not make the finding worthless. It makes it a signal. Time-restricted eating already has decent evidence for weight, and it helps keep weight off a year later. It needs a properly powered trial with brain imaging or fluid biomarkers and a design that holds weight loss equal across arms. Age likely matters too: in other work, lifestyle changes protected the brain, but only in adults under 70.
What it means for you
If you already eat in a shorter window and it works, keep going. Nothing here suggests harm, and the weight benefits are reasonably well supported. If you are picking a window, the evidence on 4-hour versus 6-hour time-restricted feeding suggests very short windows are not automatically better.
What I would not do is change when you eat because you think it will prevent dementia. That claim is not in this data. The supported version is smaller: cutting calories and losing weight is good for your aging brain, and finishing dinner a few hours before bed is cheap to try on top of that. The habits with real evidence for brain aging are still the boring ones: blood pressure control, sleep, hearing correction, exercise, and not smoking. Meal timing is a candidate, not a prescription.