The follow-up study was carried out in 2005, when the subjects had reached an age of around 40 years. A total of 1904 subjects were traced and asked to complete a general questionnaire, a food frequency questionnaire, and deliver a DNA sample, all distributed and returned through mail correspondence. The general questionnaire included questions on education, occupation, height, previous and present weight, weight loss history, physical activity, smoking, civil status, children, other family, stress, diseases, hospital admissions, and medicine use, among other things. The questions about physical activity were adopted from the baseline questionnaire. Other questions were adopted from other validated questionnaires. Moreover, a semi-quantitative, 195-item Food Frequency Questionnaire (FFQ), which previously has been used and validated in the Danish "Diet, Cancer and Health" study was included. The study was approved by the local ethics committee for Copenhagen and Frederiksberg (J.nr. KF 01-260/04).