The effect of a 2 week ketogenic diet, versus a carbohydrate-based diet, on cognitive performance, mood and subjective sleepiness during 36 h of extended wakefulness in military personnel: An exploratory study.
Level 2 - randomized trial
Randomized crossover trial
PubMed 36734405 · doi:10.1111/jsr.13832
What was done
A randomized crossover trial evaluated seven male military personnel consuming an iso-energetic ketogenic diet versus a carbohydrate-based diet for 14 days, separated by a 12-day washout period. Each dietary phase was immediately followed by 36 hours of extended wakefulness. Capillary blood glucose, D-β-hydroxybutyrate, cognitive performance (psychomotor vigilance task and running memory continuous performance test), mood, and subjective sleepiness were assessed every 2 hours during wakefulness and analyzed with linear mixed models.
What was found
D-β-hydroxybutyrate was significantly higher (p < 0.001) and glucose was significantly lower (p < 0.01) on the ketogenic diet compared with the carbohydrate-based diet. The ketogenic diet resulted in significantly improved psychomotor vigilance task performance (fewer lapses, improved mean reciprocal response time, fastest 10% response time, and slowest 10% response time; all p < 0.05), running memory continuous performance (response time and correct responses per minute; both p < 0.01), as well as improved vigor, fatigue, and sleepiness ratings (all p ≤ 0.001). Absolute numerical values were not reported in the abstract.
Why it matters
This study provides exploratory human trial evidence that nutritional ketosis may help preserve cognitive vigilance and reduce subjective fatigue during severe sleep deprivation.
Limits
The sample size is very small (n = 7) and restricted entirely to male military personnel, limiting generalizability. Absolute effect sizes, baseline diet details, and specific numerical scores were not provided in the abstract.