Accurate assessments of a target population's energy intake (EI) are essential to prevent poor nutritional status. However, self-reported dietary records (DRs) or food frequency questionnaires (FFQs) are not always accurate, thereby requiring validation and calibration studies. This study aimed to validate the EI estimated by a FFQ using the doubly labeled water (DLW) method. Participants were 109 Japanese older adults (50 women and 59 men) aged 65-88 years. The EI was obtained by a DR and 47-item FFQ over 1 year. The total energy expenditure (TEE) was measured by DLW for ~2 weeks. EI was significantly lower than TEE (p < 0.01); ratios of EI assessed by DR and FFQ against TEE were 0.91 ± 0.17 and 0.82 ± 0.22, respectively. TEE was significantly and moderately correlated with the EI estimated by the DR (r = 0.45, p < 0.01) and FFQ (r = 0.37, p < 0.01). Furthermore, the EI correlation coefficients estimated by DR and the FFQ in this study were not significantly different (p = 0.46). The EI/TEE ratio was significantly and negatively correlated with the body mass index (BMI). In conclusion, EI estimated with a DR or FFQ modestly correlated with TEE, and calibrating EI with a developed equation in this study can attenuate the underestimation of EI.
Keywords: doubly labeled water; energy intake; food frequency questionnaire; total energy expenditure; validity.