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

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.