OBJECTIVE: To investigate if long-term caloric restriction under controlled conditions adversely affects cognitive function in obese women. SUBJECTS: Healthy, premenopausal women between 23±42 y. Dieting group: n 14. Control group: n 11. DESIGN: Longitudinal weight loss study (repeated measures within-subject design) with 3 weeks of baseline, 15 weeks of 50% caloric restriction, and 3 weeks of weight stabilization. MEASUREMENTS: Computerized cognitive function tests (sustained attention, short-term memory, simple reaction time, motor performance and attentional focus), height, body weight, body composition (TOBEC) and behavioral questionnaires (Dutch Eating Behaviour Questionnaire, Eating Attitudes Test, and State-Trait Anxiety Inventory). RESULTS: Dieting women lost 12.3 AE 5.5 kg (mean AE s.d.) of body weight. Controlled long-term caloric restriction signi®cantly slowed simple reaction time but did not diminish sustained attention, motor performance or immediate memory. Word recall performance signi®cantly improved by 24% at the end of caloric restriction. CONCLUSIONS: The slowing of simple reaction time is a short-term and long-term consequence of caloric restriction. In contrast to previous short-term dieting studies, sustained attention and immediate memory were not impaired with long-term caloric restriction.

The current study investigated the relationships between blood glucose levels, mild food deprivation, sympathetic arousal, and cognitive processing efficiency. Subjects (n = 82) were randomly assigned to four experimental conditions, comprising combined manipulations of food deprivation and incentive motivation. Baseline and mid-session measurements of blood glucose, blood pressure and pulse rate were taken. Subjects completed a number of measures of cognitive processing efficiency and self report measures of affective and somatic state. Although glucose levels were lowered following food deprivation, there was no significant detrimental effect of food deprivation on task performance. However, improved recognition memory processing times were associated with deprivation. Incentive motivation was associated with faster simple reaction times and higher diastolic blood pressure. There were no significant relationships between glucose levels and task performance, further supporting the hypothesis that the brain is relatively invulnerable to short food deprivation.

Objective: To determine the relationships between cognitive function and iron status in dieting obese women. Design: Longitudinal weight loss study (repeated measures within-subject design) with 3 weeks of baseline, 15 weeks of 50% caloric restriction, and 3 weeks of weight stabilization. Dietary iron was fed at twice the US Recommended Dietary Allowance with half of the iron from food sources and half from an oral supplement. Setting: This was a free-living study with the exception that subjects came to the research center for one meal per day and were provided all other meals and snacks to take home. Subjects: Healthy, premenopausal, obese women (mean BMI 31.5) were recruited through local newspaper, poster and radio advertising. Twenty-four women volunteers were recruited and 14 completed the study. Measurements: Cognitive function, iron and hematological status, height, body weights and body composition were measured at baseline; at weeks 5, 10, and 15 of the energy restriction period; and at the end of weight stabilization. Computerized cognitive tests included: Bakan vigilance task, two ®nger tapping, simple reaction time, immediate word recall, and a focused attention task. Iron status and hematological measures included: serum iron, total iron binding capacity (TIBC), transferrin saturation, serum ferritin, hemoglobin (Hb), hematocrit, red cell count, MCV, MCH, MCHC, and RDW. Results: A signi®cant reduction in Hb, hematocrit, and red blood cell count occurred across the study. Hb at the end of the study was positively correlated (r = 0.72, P < 0.01) with mean performance on a measure of sustained attention. Transferrin saturation also correlated positively to sustained attention task performance for those subjects whose Hb declined across the study (r = 0.86, P < 0.01). Conclusions: These ®ndings suggest that dieting diminishes iron status in obese women, even when suf®cient dietary iron is available, and that the inability to sustain attention may be an early sign of developing iron de®ciency in dieting women.