It is well established that diet, meaning which foods we eat, impacts brain health, but there is increasing evidence that what time we eat may be nearly as important. While altering your eating schedule will not counteract the negative effects of a poor diet, it may help amplify the beneficial effects of a healthy diet.
Every cell in the body cycles its activity according to an internal clock. These clocks are synced to a daily cycle based on the rising and setting of the sun [1]. This natural rhythm, called the circadian rhythm, influences the physiology of the body, such that the cells of the body are optimized to engage in specific tasks during certain periods of the cycle. In general, the human body is primed to be active during the day and to rest during the night. Since eating is an active process, our bodies are designed to utilize nutrients most efficiently during the daytime hours [2]. As the evening approaches, the body shifts its priorities to healing and repair. This means that during the night, the cells in the body have a lower capacity to take up and use nutrients from food. This can result in elevated levels of nutrients circulating in the blood, which can induce a stress response [3]. Instead of being used by cells, these excess sugars and fats get stored in fat tissue, resulting in weight gain. In this way, chronic nighttime eating can prime the body toward metabolic disorders, such as diabetes and obesity, which are established risk factors for dementia. Numerous clinical studies have found that shifting eating patterns back into alignment with the day-night cycle, whereby food is primarily consumed during the daytime hours, can improve measures of metabolic health [4].
The adage that ‘breakfast is the most important meal of the day’ may stem from the health benefits associated with eating during the morning and afternoon hours, relative to eating during the evening. Skipping breakfast, which is generally an indication of a later-shifted eating pattern, has been associated with an increased risk for cardiovascular disease [5], while late-night eating has been associated with an increased risk for some forms of cancer [6]. Recent studies provide evidence that eating patterns may also impact cognitive function. An observational study found that older adults who restricted their daily eating to a window of no more than ten hours were less likely to show signs of cognitive impairment [7]. Notably, the association was driven by those with an early-shifted eating window. A separate study found that skipping breakfast was associated with a faster rate of cognitive decline in older adults [8].
Eating out of sync with the natural rhythm disrupts the internal clocks by altering cellular activity patterns, which can negatively impact cell function [2]. In the brain, cellular rhythms play an important role in the mechanisms underlying learning and memory, such that disruptions to these rhythms can impair cognition [9]. Meal timing can also influence the production of hormones involved in regulating the sleep-wake cycle [10]. Consequently, late night eating can make it more difficult to fall asleep and reduce sleep quality, which can also negatively impact brain function.
Modern society has led to an extension of our activity patterns beyond our natural rhythms, which has caused our bodies to fall out of sync, placing us at higher risk for chronic age-related diseases. While it is not feasible to rearrange all aspects of our lives to coincide with the light-dark cycle, realigning eating patterns with the day-night cycle, which involves restricting eating to a window of eight to twelve hours biased toward the morning and afternoon, can help restore our internal rhythms and maintain our health.
Betsy Mills, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Mills came to the ADDF from the University of Michigan, where she served as the grant writing manager for a clinical laboratory specializing in neuroautoimmune diseases. She also completed a Postdoctoral fellowship at the University of Michigan, where she worked to uncover genes that could promote retina regeneration. She earned her doctorate in neuroscience at Johns Hopkins University School of Medicine, where she studied the role of glial cells in the optic nerve, and their contribution to neurodegeneration in glaucoma. She obtained her bachelor's degree in biology from the College of the Holy Cross. Dr. Mills has a strong passion for community outreach, and has served as program presenter with the Michigan Great Lakes Chapter of the Alzheimer's Association to promote dementia awareness.
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