15-day fasting and aerobic exercise impair cognitive abilities and mental states

Long-term complete fasting (≥ 4 days) is an extreme condition which may happen in emergent situations, requiring exerted cognitive functioning and maintain strength to solve problems. However, there is still no clear understanding how long-term fasting and physical activities affect people’s cognitive functions and their mental states. In the current study, 22 healthy participants completed a 28-day experiment (7 females and 15 males; age: 41 ± 7 years old; BMI: 24.84 ± 2.52). The whole experiment includes 3-day Baseline, 15-day Complete Fasting, 5-day Caloric Restriction and 5-day Full Recovery phases. Participants were randomly assigned into three groups with gender and BMI balanced across groups: Group EM with supervised moderate intensity of running (= 5 km/h) during Complete Fasting (2 F and 5 M; age: 40 ± 8; BMI: 25.40 ± 3.04); Group EL with supervised light intensity of running (= 3 km/h; 3 F and 5 M; age: 41 ± 7; BMI: 25.19 ± 2.62); Group CN without any exercise (2 F and 5 M; age: 43 ± 7; BMI: 23.89 ± 1.84). During the whole experiment, Go/No-go, Time Perception and Auditory Serial Reaction Time tasks were used to track participants’ cognitive functions and visual analogue scale was used to measure their mental states. Results showed that fasting impaired executive and learning functions, and the inclusion of exercises further impaired the learning function. However, this cognitive decrease in inhibitory control due to fasting was not a linear trend but rather followed a double hump pattern, which may reflect the influence of metabolic changes from glucose to ketone. Additionally, fasting increased subjective feelings of sleepiness and decreased calmness, and no significant differences were observed among exercise groups. This study is the first to combine long-term complete fasting and exercises, offering insights into fasting protocols and survival strategies in food-shortage emergencies.