My dad always stressed the importance of eating breakfast before school, insisting that an empty stomach would “dull my brain and make learning much harder.” I dutifully ate my oats—but was he right?

There are two main theories about how fasting could affect the brain. One hypothesis suggests that fasting drains the brain's cognitive resources, making it harder to focus on tasks unrelated to hunger. Hunger could become a distraction, causing people to make poorer decisions or struggle with complex tasks. On the other hand, some research shows that hunger may sharpen decision-making, especially regarding food choices.

This study specifically examines the effects of short-term fasting, looking at whether a brief period without food impacts cognitive ability.

The study
Researchers conducted an experiment with 245 participants to assess if fasting, induced by either 3-hour or 12-hour periods without food, has any measurable impact on cognitive performance.

The study also looked at potential differences in how fasting affects individuals based on characteristics such as Body Mass Index, race, and their personal associations with food.

The study used a test that measured abstract reasoning to assess cognitive performance in participants after different fasting durations.

Results showed no significant decline in cognitive ability after fasting for either 3 hours or 12 hours, suggesting that short-term fasting does not impair short-term cognitive function. The experiment also found little variation in how fasting affected individuals based on factors like body weight or race. 

Fasting and Cognitive Performance
Previous research has shown that longer periods of fasting or chronic food scarcity can negatively affect cognitive functions such as attention, memory, and problem-solving. The study’s findings challenge the assumption that short-term food deprivation leads to a noticeable drop in cognitive ability.

It indicates that while hunger might impact decision-making in certain contexts, it does not seem to hinder basic cognitive tasks that require fluid intelligence.

The lack of a significant cognitive penalty after short fasting suggests that the timing and duration of food deprivation may be crucial factors.

So .. to oat or not to oat?
The study contributes to ongoing research on intermittent fasting and its effects on both health and cognitive function.

While short-term fasting has been linked to various health benefits, including weight loss and cholesterol reduction, this study provides evidence that it does not significantly impair cognitive ability in the short run.

Given the growing popularity of intermittent fasting, especially for health or religious reasons, these findings suggest that fasting for up to 12 hours is unlikely to have a substantial cognitive cost.

About the scientific paper:

First author: Austin Landini, USA
Published in: PLoS One. November 2024. 
Link to paper: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0312811