To investigate if long-term caloric restriction under controlled conditions adversely affects cognitive function in obese women. Healthy, premenopausal women between 23-42 y. Dieting group: n = 14. n = 11. 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. 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). Dieting women lost 12.3 +/- 5.5 kg (mean +/- s.d.) of body weight. Controlled long-term caloric restriction significantly slowed simple reaction time but did not diminish sustained attention, motor performance or immediate memory. Word recall performance significantly improved by 24% at the end of caloric restriction. 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.