OBESITY AS A MAJOR DETERMINANT OF UNDERREPORTING IN A SELF-ADMINISTERED FOOD FREQUENCY QUESTIONNAIRE - RESULTS FROM THE EPIC-POTSDAM STUDY

The phenomenon of underreporting of dietary intake has been observed p reviously in many epidemiologic studies. In this study it was investig ated whether dependencies exist between energy intake obtained by a se miquantitative, self-administered food frequency questionnaire and lif estyle or anthropometric factors, particularly obesity. The study popu lation consisted of 2 531 subjects, men aged 40 to 64 years and women aged 35 to 64 years from the general population of Potsdam and the sur rounding areas. First, subjects were allocated into quintiles of the r atio 'reported energy intake (EI)' to 'calculated basal metabolic rate (BMR)' as a measure of age and weight adjusted energy intake. No appa rent dependencies between socio-economic variables and the ratio EI/BM R were observed. Among anthropometric variables, BMI and related measu res of obesity were inversely related to the ratio EI/BMR in men and w omen. While dietary intake was directly related to the ratio EI/BMR in absolute quantities, energy adjusted intake of fat, protein, carbohyd rate, and alcohol was found to be independent of this ratio. Energy ad justed food group consumption was also found to be independent of the ratio EI/BMR, showing only slightly increasing trends across quintiles of EI/BMR for cereals and fats, and a slightly decreasing trend for s weet foods in women. When subjects were classified into three categori es of BMI, reported energy intake decreased across categories. Estimat ed energy expenditure based on BMR was increasing with BMI categories. A close direct relationship was observed between BMI categories and t he difference between reported energy intake and estimated energy expe nditure. It is concluded that obesity is a major determinant of underr eporting. Energy adjusted dietary variables were found to be largely i ndependent of such methodological influences.