Estimating under-reporting of energy intake in dietary surveys using an individualised method
Under-reporting (UR) of energy intake (EI) by self-reported dietary methods is well-documented but the methods used to estimate UR in population-based studies commonly assume a sedentary lifestyle. We compared estimated UR using individualised estimates of energy requirements with a population cut-off based on minimum energy needs. UR was estimated for 1551 adults aged 19–64 years enrolled in the National Diet and Nutrition Survey. Physical activity diaries and 7 d weighed dietary records were completed concurrently. Mean daily EI (kJ/d) was calculated from the dietary records. Reported physical activity was used to assign each subject’s activity level, and then to calculate estimated energy requirements (EER) from published equations. UR was calculated both as EER – EI with an adjustment for daily EER and EI variation, and also by a population method. By the individual method UR was approximately 27% of energy needs in men and 29% in women, with 75% of men and 77% of women classified as under-reporters; by the population method 80 and 88% were classified as under-reporters respectively. When subjects who reported their eating being affected by dieting or illness during dietary recording were excluded, UR was 25% of energy needs in both sexes. UR was higher in overweight and obese men and women compared with their lean counterparts (P,0·001). UR of EI must be considered in dietary surveys. The EER method allows UR to be quantified and takes into account an individual’s activity level. Measures of physical activity and questions to identify under-eating during dietary recording may help to evaluate secular trends in UR.