Submitted to: Lancet
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/3/2005
Publication Date: 5/3/2005
Citation: Green, M.W., Elliman, N.A., Kretsch, M.J. Weight loss strategies, stress, and cognitive function: supervised versus unsupervised dieting. Lancet. Elsevier, Psychoneuroendocrinology (2005) 30, 908-918. Interpretive Summary: In the United States and in many populations around the world, the incidence of obesity has increased dramatically, reaching epidemic proportions. Not surprisingly, there has been considerable interest in preventing and reducing the incidence of obesity. However, a number of studies have shown that weight loss is not without negative psychological consequences. For instance, dieting has been associated with increased depression, lowered self-esteem, and poorer cognitive abilities. In an effort to better understand the relationship between dieting and cognitive impairment, this study investigated the effect of dieting conditions on cognitive performance. Further, the study examined whether or not the stress of dieting leads to an elevation in body cortisol levels, one factor that may underlie alterations in cognitive function. Three groups of healthy, pre-menopausal, overweight women were studied: those dieting unassisted, those dieting with the support of a commercial weight loss program, and non-dieting controls. After one week of dieting, the unsupervised dieters had poorer concentration and planning abilities and significantly elevated body cortisol levels. These changes were not observed in the other groups. This research affirms the need to develop effective weight loss strategies without adverse functional consequences.
Technical Abstract: Background Dieting to lose weight has been associated with neuro-psychological impairments in the early stages of attempted weight loss, consistent with a reduction in working memory capacity. Previous work has not elucidated whether these impairments are a function solely of unsupported or supported dieting. Previous work also indicates that these impairments could be a function of raised cortico-steroid levels. Methods Healthy, overweight, pre-menopausal women were randomised to one of three conditions in which they either dieted as part of a commercially available weight loss group, dieted without any group support or acted as non-dieting controls for a period of eight weeks. Testing occurred at baseline and again after one, four and eight weeks. During each session, participants completed measures of neuro-psychological function including measures of simple reaction time, motor speed, vigilance, immediate verbal recall, visuo-spatial processing and (at week one only) executive function. Participants donated saliva samples, later assayed for cortisol, at the beginning and thirty minutes into each test session. Also, food intake was self-recorded prior to each session and fasting body weight and percentage body fat were measured at each session. Findings Participants in the unsupported diet condition displayed poorer vigilance performance and impaired executive planning function (along with a marginally significant trend for poorer visual recall) after one week of dieting. No such impairments were observed in the other two groups. In addition, the unsupported dieters experienced a significant rise in salivary cortisol levels after one week of dieting, which significantly correlated with task performance. Both dieting groups lost roughly the same amount of body weight over the course of the eight weeks of dieting, although only the unsupported dieters experienced a significant drop in percentage body fat over the course of dieting. Interpretation Unsupported dieting is associated with increased stress during its early stages, and it is this elevation in the cortisol level which is responsible for the observed impairments in cognitive task performance.