Fasting and cognition in well- and undernourished schoolchildren: a review of three experimental studies

This paper reviews three experiments on the effects of an overnight and morning fast on attention and memory processes among 9-11-y-old children. Two of the experiments focused on middle-class, well-nourished boys and girls in the United States; the third involved boys from low-income families with and without nutritional risk in Huaraz, Peru. All experiments used the same crossover design and followed similar experimental procedures to control the subjects' intakes and motor activity during the study period. The children were admitted to a research center on two different evenings, approximate to 7 d apart. After arrival the children ate dinner, played table games or watched television, and went to bed. They were awakened at 0730 and, by design, were either served breakfast (approximate to 2301 kJ) or not. At 1100 they took psychologic tests that assessed recall from working memory and competence in discriminating visual stimuli. At 1200 the children were discharged. The consequences of the overnight and morning fast, particularly among the children who were nutritionally at risk, included slower stimulus discrimination, increased errors, and slower memory recall. We propose that these alterations result from a state of metabolic stress in which homeostatic mechanisms work to maintain circulating glucose concentrations.