The effect of mild dehydration (1–3% loss of body weight as water)
on subjective ratings of perceived physiological and mood states has
been investigated during drinking restriction. As expected,
dehydration state increases perceived thirst and mouth dryness.
Dehydrated subjects also scored lower on alertness and on their ability
to concentrate while they scored higher on fatigue, as compared to
hydrated controls. These results confirmed previous observations.
The physiological changes and/or physical discomfort induced by
moderate dehydration seem, therefore, to negatively influence
subjective perceptions of mental energy.