For people trying to lose weight, eating less may not be the only benefit. A small randomized trial suggests that restricting meals to an earlier, shorter window could also sharpen planning, problem-solving, and other aspects of executive function, even when both groups lose about the same amount of weight.
To find out, the researchers recruited 47 postmenopausal women who were overweight or obese, and split them into two groups. Both groups cut out 500 calories a day from their diets. One group ate within a normal 12-hour window—for example, breakfast at 7:30 a.m. and nothing after 7:30 p.m. The other limited eating to a shorter window earlier in the day, nine hours or less, with most eating within eight hours, finishing their last meal about four hours before bed.
The Results
After six months, both groups lost about the same amount of weight, but only one group showed cognitive improvement. On a battery of cognitive tests, the early, time-restricted eating group scored significantly better on problem-solving and planning—a cluster of skills researchers call executive function. That covers things like working memory, mental flexibility, resisting impulses, and strategic thinking. Memory and learning improved too. Reaction time and multitasking didn’t improve, and neither did sleep quality in either group.
The results were substantial. “I felt surprised because it’s hard to get significant findings—and we found them,” Sue Shapses, study author, a professor of nutritional sciences, and director of the Center for Human Nutrition, Exercise and Metabolism at Rutgers University, told The Epoch Times.
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Executive function alone encompasses working memory, cognitive flexibility, inhibitory control, planning, problem-solving, strategic thinking, and impulsivity assessment. “And that’s a really big one to get a significant effect on, and so it was very interesting,” she said.
Why Timing Might Matter
The study wasn’t designed to prove why timing helped, but researchers have a leading theory: circadian rhythm. Our bodies run on an internal clock, and nearly every organ has its own daily cycle that affects how well it functions.
There is a master clock in the brain—in a region called the suprachiasmatic nucleus—that is activated by light entering the eyes and governs sleep, body temperature, metabolism, and hormone production. The organs also have their own local clocks, called “peripheral clocks.” What we eat and when we eat help set those. Normally, the master and peripheral clocks stay in sync, but eating at odd hours can throw them out of alignment.
Betsy Mills, a neuroscientist and associate director of the Aging and Alzheimer’s Prevention Program at the Alzheimer’s Drug Discovery Foundation, who was not involved in the study, told The Epoch Times that the combined evidence so far suggests the brain benefits of restricted eating are strongest when the eating window is shifted earlier in the day—a concept researchers call “chrononutrition.”
Mills said the brain benefits of time-restricted eating appear to depend on aligning meals with the body’s natural circadian rhythm by eating earlier in the day and avoiding late-night meals.
A Caveat, and What’s Next
Both researchers caution that diet quality still matters—a shorter eating window isn’t a substitute for eating well. Mills points to eating whole foods like vegetables, fruits, whole grains, and fish, and cutting back on sugar and ultra-processed foods, as important measures. Shapses is also careful about drawing conclusions because the findings are preliminary and still being analyzed.
Based on the study’s findings, Shapses wants to investigate the mechanisms underlying timed eating and test whether the cognitive benefits also occur in people who aren’t trying to lose weight, since this trial only included women actively losing weight.
