Impaired cognitive processing in dieters: Failure of attention focus or resource capacity limitation?

Objectives. The current study investigated the fundamental nature of the cognitive processing deficit associated with spontaneous dieting behaviour. Design. In a between-subjects design, dieters and non-dieters performed a number of cognitive performance tasks designed to test the competing hypotheses that the deficit in performance previously observed in dieters is due either to resource capacity limitation or to a failure to maintain attentional focus. Methods. Current dieters (N = 21), non-dieting restrained eaters (N = 20) and non-dieting low-to-medium restrained eaters (N = 28) completed measures of working memory span, attentional focus and motor speed. Participants also completed self-report measures of dietary restraint, somatic sensation and affective state. Results. Dieters displayed a significantly smaller working memory span than non-dieting participants with a similar level of dietary restraint, which covaried with their self-rated 'Desire to eat'. Conclusions. The cognitive impairments found to be associated with dieting behaviour result from a reduction in working memory processing capacity. It is suggested that this, in turn, results from task-irrelevant cognitions concerning food preferentially consuming limited processing capacity.