Stable cognitive performance while adapting to intermittent fasting: A randomised controlled trial

TL;DR

A 10-day study found that 16-hour intermittent fasting does not impair cognitive performance or mood, though concentration was lower before noon.

Contribution

This study provides new evidence that long-term intermittent fasting does not harm cognitive performance or mood.

Findings

Fasting participants showed no lower cognitive performance compared to controls.

Participants reported lower concentration before noon while fasting.

Mood was not negatively affected by intermittent fasting.

Abstract

Intermittent fasting (IF) is a popular health regimen for weight loss and overall health. Yet, potential negative side effects on cognition and mood could hinder its adoption. Such side effects, however, have so far only been studied in short term exposures to IF. We tested whether fasting impairs cognitive performance and mood when adapting to 16-hour, breakfast-skipping IF over 10 days in a randomised, waitlist-controlled trial (N = 122). Cognitive performance was repeatedly assessed online via standardised psychological tasks and subjective concentration and mood measured twice daily via smartphone questionnaires. Bayesian multi-level modelling revealed that fasting participants did not have lower cognitive performance or mood compared to control participants. However, participants felt less concentrated while fasting before noon, compared to after breaking the fast in the afternoon. Thus, 16-hour IF does not cause cognitive performance or mood deficits, removing a potential concern in its use as a health intervention.

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