Skipping Breakfast Doesn’t Impair Mental Clarity, New Research Finds

A comprehensive review of existing studies published today indicates that regularly skipping breakfast does not negatively impact cognitive function, challenging long-held beliefs about the importance of morning meals.

Researchers analyzed 71 studies encompassing nearly 3,500 participants, comparing the cognitive performance of those who fasted or had recently eaten, focusing on memory, decision-making, response time, and accuracy. The analysis, appearing in the journal Psychological Bulletin, revealed no significant difference in cognitive abilities during short-term fasts averaging around 12 hours. “The idea that fasting interferes with mental performance probably stems from how we feel when hungry—tired, distracted, and irritable,” explains David Moreau, PhD, associate professor in the School of Psychology at the University of Auckland in New Zealand. “It’s natural to assume that those sensations reflect poorer cognitive function. Some early studies supported this view, but when you pool the evidence, those effects largely disappear.” This finding could have implications for the growing popularity of intermittent fasting as a weight-management strategy.

However, the study did find that longer fasts – exceeding 24 hours – may lead to slight declines in cognitive performance. The brain adapts by utilizing ketone bodies derived from fat as an alternative fuel source when glucose stores are depleted, but this process isn’t as efficient during prolonged periods without food. “Fasts that last longer than 24 hours may negatively affect cognitive performance,” adds Sonya Angelone, PhD, RDN, a consulting nutritionist. Individuals new to fasting or those with metabolic conditions like diabetes may experience temporary mental fogginess as their bodies adjust, similar to how the body reacts to changes in diet, as explained by registered dietitian Albert Matheny, RD, CSCS. For more information on metabolic health, visit the Centers for Disease Control and Prevention.

Researchers emphasize the brain’s remarkable ability to maintain function even without immediate access to glucose. “Your brain metabolism is prioritized over other parts of your body so, if you fast, your brain gets fed before your muscles,” explains Clifford Segil, DO, a neurologist at Providence Saint John’s Health Center. Understanding how the brain utilizes different fuel sources is crucial for optimizing cognitive performance, and further research into the long-term effects of various fasting regimens is ongoing; you can learn more about the science of fasting here.

Officials stated that continued research will focus on individual responses to fasting and the potential benefits for neurological health.