Impaired cognitive functioning during spontaneous dieting

Abstract

SYNOPSISIn one of a continuing series of studies, the cognitive performance of normal weight female dieters was compared on two sessions, 3 weeks apart. Those who reported themselves as being on a weight-reducing diet on only one of the two sessions displayed poorer vigilance performance, slower reaction times and poorer immediate recall of words when they were dieting. In contrast, performance on a low processing load tapping task was unaffected. Self-report measures showed that dietary restraint, but not state anxiety or depression was increased during dieting. These results are interpreted in terms of an association between dieting behaviour and high levels of distractibility, and extend earlier findings by demonstrating that these deficits in cognitive performance are closely related to dieting or the perceived need to diet per se.

Cognitive effects of a long-term weight reducing diet

“…Whereas poorer immediate memory was found in the short-term, self-imposed dieting studies, 3,5 no such change was found with long-term caloric restriction in either this study or the Minnesota study. 13 Rather, in this study recall performance signi®cantly improved at the end of caloric restriction ( 24%) and then readily reversed to baseline levels upon restoration of suf®cient calories to maintain body weight.…”

“…13 Rather, in this study recall performance signi®cantly improved at the end of caloric restriction ( 24%) and then readily reversed to baseline levels upon restoration of suf®cient calories to maintain body weight. It could be that if changes in immediate memory occur, as reported in the earlier studies, 3,5 they occur only during the early weeks of dieting. In this study, subjects with the greatest body weight loss after 5 weeks of caloric restriction had the lowest two second word recall scores (r 0.72, P 0.004), however, this relationship was not found after 10 or 15 weeks of caloric restriction.…”

“…3,5 The sustained attention task employed in those studies was the Bakan vigilance test, a high processing load attention task. Contrary to those studies, no signi®cant change in Bakan vigilance task performance was found in this study in which the Bakan testing was begun ®ve weeks into the dieting period.…”

“…3 Further, it has been found that, within the same individuals performance on a cognitive function task battery was poorer when they reported themselves as currently dieting than when they reported themselves as not currently dieting. 5 This demonstrates that the processing impairments were associated with self-imposed dieting per se, rather than being due to pre-existing differences between dieters and non-dieters. Since the dieters in this latter study reported no substantial weight loss from their self-imposed diet, it was also tentatively concluded that the underlying nature of the processing impairment was primarily psychological, rather than physiological.…”

Are dieting-related cognitive impairments a function of iron status?

“…The main finding of the present study was the replication of the impairment in cognitive function among unsupported dieters, relative to supported dieters or non-dieting controls, within the first week of attempted weight loss (7,15) . Primarily, the impairments appear to be in tasks which assess the capacity of the central executive and phonological loop components of working memory (12) , although simple reaction speed also appeared to be impaired in unsupported dieters during the early stages of weight loss (6) .…”