Dietary assessment in the 1993 Pelotas (Brazil) birth cohort study: comparing energy intake with energy expenditure

The study aims to describe and compare two methods of energy intake assessment and one measure of energy expenditure applied in adolescents from a birth cohort. In a sub-sample of the 1993 Pelotas (Brazil) birth cohort, followed up in 2006-7, information on intake was obtained through a food-frequency questionnaire (FFQ) and three 24-hour-recalls (24hR), while energy expenditure was assessed using an accelerometer. Bland & Altman plots were used in the analyses in order to compare the methods. The mean difference between FFQ and 24hR was 592 +/- 929cal/day. Compared to energy expenditure, intake was overestimated when measured by FFQ (357 +/- 968cal/day) and underestimated by 24hR (-278 +/- 714cal/day). In spite of the great differences between energy intake obtained using the two methods, lower differences were observed when these methods were compared to expenditure.