In June 2019 researchers from the USA published the results of their study to assess cognitive control during periods of sustained physical exertion and limited caloric intake. The researchers stated that it is known that cognitive function is preserved during short-term calorie restriction, but it is unclear if preservation of congnitive function extends to combined calorie restriction and physical exertion. A total of 23 individuals had limited calorie intake for two days on one occasion and were fully fed on another. During this time intermittent bouts of exercise at 40-65% VO2 peak were undertaken, with cognitive function, mood and perceived exertion being assessed. Results showed that limitation of calories impaired accuracy on the task-switching task and decreased sensitivity on the go/no-go task. However a limitation of calories did not appear to affect risk taking on the risk taking task. During exercise, a limitation of calories, especially on day 2, increased perceived exertion and impaired mood states of tension, depression, anger, vigour, fatigue, and confusion. The researchers therefore concluded that physical exertion during times of limited calorie intake impairs cognitive control, mood and perceived exertion.
Giles GE et al. Two days of calorie deprivation impairs high level cognitive processes, mood, and self-reported exertion during aerobic exercise: A randomized double-blind, placebo-controlled study. Brain Cogn. 2019 Jun;132:33-40.