Does Frequently Skipping Breakfast Affect Concentration?
A recent review published in Psychological Bulletin suggests that skipping breakfast regularly doesn’t necessarily hinder mental focus. Researchers claim there’s substantial evidence indicating that short-term fasting doesn’t impair mental clarity.
David Moreau, an associate professor at the University of Auckland and coauthor of the study, comments, “The belief that fasting disrupts mental performance likely comes from how we feel when hungry—often tired, distracted, and irritable. It’s easy to connect those feelings with diminished cognitive function. Early studies endorsed this idea, but a comprehensive review shows those effects mostly vanish.”
This might be welcome news for those exploring intermittent fasting but feeling anxious about experiencing brain fog. However, there are different effects regarding short-term and long-term fasting on cognitive function; it’s worth discussing further.
Short-Term vs Long-Term Fasting: What’s Better for Cognition?
In their analysis, researchers reviewed 71 studies involving nearly 3,500 participants who were either fasting or had recently eaten. They looked into various cognitive abilities, including memory, decision-making, response time, and accuracy. Most fasting instances were short-term, typically lasting around 12 hours.
The findings revealed no significant cognitive performance differences between those who fasted for shorter periods and those who had recently eaten. “The brain has built-in mechanisms to stay energized, even when food is scarce—a comforting insight for intermittent fasting practitioners,” remarks Moreau.
In contrast, those engaging in longer fasting—especially beyond 12 hours—experienced a slight decline in cognitive performance.
“Fasts lasting over 24 hours may negatively impact cognitive function,” says Sonya Angelone, a consulting nutritionist. Still, the study indicates that short-term intermittent fasting is generally safe for most individuals.
But What If You Feel Unfocused When Fasting?
The study indicates no cognitive differences for those accustomed to short-term fasting. Yet, if you’re new to this practice, your body might need time to adjust. Albert Matheny, a registered dietitian, explains that initial fasting might leave you feeling mentally unsettled.
“For those who don’t typically fast, it can be especially challenging,” he notes. “If you’re used to regular meals and suddenly don’t eat, the hunger can be quite distracting.” Those with metabolic issues, such as diabetes, might also find that their cognitive abilities are affected during intermittent fasting.
How Does Fasting Affect the Brain?
Fasting impacts the brain, but not in terms of cognitive capabilities, which involve thinking, learning, and remembering.
Typically, the brain relies on glucose derived from glycogen. When fasting, this energy source diminishes, yet the brain is “remarkably adaptable” and has a response plan.
When glycogen levels drop, the body begins converting fat into ketone bodies—an alternative fuel source for the brain, as Moreau explains.
“Your brain’s needs are prioritized over those of other body parts; during fasting, your brain receives energy before your muscles do,” shares Clifford Segil, a neurologist.
According to Moreau, this adaptability ensures a consistent energy supply to the brain, even when food is not available. “Evolutionarily, this makes sense; our ancestors needed to remain alert while foraging and couldn’t afford to feel sluggish,” he notes. “That ability to maintain cognitive stability seems to persist even today.”
