COGNITIVE FUNCTION, IRON STATUS, AND HEMOGLOBIN CONCENTRATION IN OBESE DIETING WOMEN

Objective: To determine the relationships between cognitive function a nd iron status in dieting obese women. Design: Longitudinal weight los s study (repeated measures within-subject design) with 3 weeks of base line, 15 weeks of 50% caloric restriction, and 3 weeks of weight stabi lization. Dietary iron was fed at twice the US Recommended Dietary All owance with half of the iron fr-om food sources and half from an oral supplement. Setting: This was a free-living study with the exception t hat 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 lo cal newspaper, poster and radio advertising. Twenty-four women volunte ers were recruited and 14 completed the study. Measurements: Cognitive function, iron and hematological status, height, body weights and bod y composition were measured at baseline; at weeks 5, 10, and 15 of the energy restriction period; and at the end of weight stabilization. Co mputerized cognitive tests included: Bakan vigilance task, two finger tapping, simple reaction time, immediate word recall, and a focused at tention task. Iron status and hematological measures included: serum i ron, total iron binding capacity (TIBC), transferrin saturation, serum ferritin, hemoglobin (Hb), hematocrit, red cell count, MCV, MCH, MCHC , and RDW. Results: A significant reduction in Hb, hematocrit, and red blood cell count occurred across the study. Hb at the end of the stud y was positively correlated (r = 0.72, P < 0.01) with mean performance on a measure of sustained attention. Transferrin saturation also corr elated positively to sustained attention task performance for those su bjects whose Hb declined across the study (r = 0.86, P < 0.01). Conclu sions: These findings suggest that dieting diminishes iron status in o bese women, even when sufficient dietary iron is available, and that t he inability to sustain attention may be an early sign of developing i ron deficiency in dieting women.