Intermittent fasting offers those, who are looking to gain some control over their calories, a chance to manage their food intake while making space to digest those all-important nutrients. But when it comes to choosing a winning fasting window, it can be difficult to know which protocol to plan for. Fortunately, a new study by the American Society of Nutrition may have the answer as relates to the top method of time restriction, with results showing that an eight-to-nine-hour window could benefit both body and brain.
The study, presented at the Nutrition 2026 meeting in Washington, D.C. aimed to find out if time-restricted eating could alleviate the risk of dementia while aiding in weight loss and improving cognitive function. This is an important link to make, because those who are overweight or obese have a greater likelihood of developing Alzheimer’s disease and other forms of dementia.
How was the Study Carried Out?
47 overweight or obese women, between the ages of 50 and 79, were supported with reducing their overall intake by 500 calories per day, and split into two groups for six months:
Group One: Eating was restricted to less than 9 hours per day
(10am to 6pm)
Group Two: Typical eating window of around 12 hours per day
(No window of restriction)
What is the Optimal Intermittent Fasting Window for Weight Loss and Brain Health?
At the end of the six months, the average weight loss among both groups, having shaved 500 calories off their usual daily intake, resulted in about the same amount of weight loss, averaging 15 pounds. But when it came to brain function, restricting daily eating to an 8-to-9-hour window combined with cutting 500 calories daily delivers the best balance of fat loss and cognitive enhancement.. They demonstrated better problem-solving abilities and had greater memory recall, although there was no significant difference in multitasking or reaction times between the groups.
“There was a modest effect of time-restricted eating to improve spatial planning and problem-solving, and on reducing errors related to memory and learning,” said Professor Sue Shapses, who was the study’s principal investigator. “These outcomes suggest a better ability to remember information during everyday tasks and reducing mistakes related to memory, attention and problem-solving.”
How Time-Restricted Eating Protects Cognitive Performance
While losing weight alone is a great way to boost longevity and slow mental and physical decline, the experts think that stopping eating, around 4 hours prior to sleep, could be one of the biggest reasons that fasting comes into its own. “Reductions in the eating window predicted greater improvements,” said Professor Shapses.
Since this latest study was relatively small in size, further work will likely involve a larger sample, including men, with a greater focus on other elements that may impact the effects of fasting, such as the impact on our circadian rhythm, nutrient sensitivity, inflammation, and metabolic health. But for now, there’s strong evidence to suggest that sticking with a time restricted window of 8 to 9 hours, and finishing your food around four hours before bedtime, could boost brain longevity while helping to lose weight.
