An estimation of periconceptional under-reporting of dietary energy intake.

BACKGROUND The purpose of this cross-sectional study was to examine periconceptional misreporting of energy intake (EI) using the Willet food frequency questionnaire (WFFQ). METHODS Women were recruited in the first trimester. Women completed a semi-quantitative WFFQ. Maternal body composition was measured using eight-electrode bioelectrical impedance analysis. Under-reporters were those whose ratio of EI to their calculated basal metabolic rate fell below the calculated plausible threshold for their physical activity category. RESULTS The mean age was 30.1 ± 5.3 years (n = 524). The mean body mass index (BMI) was 25.4 ± 5.6 kg/m(2), and 16.6% were obese (BMI ≥ 30.0 kg/m(2)). Under-reported EI was observed in 122 women (23.3%) with no over-reporters in the sample. Under-reporters were younger (P < 0.001), less likely to have a normal BMI (P = 0.002) and more likely to be obese (P < 0.001) than plausible reporters. Under-reporters had higher percentage of body-fat and lower percentage of body fat-free mass (P < 0.001), were more likely to be at risk of relative deprivation (P = 0.001) and reported a higher percentage of EI from carbohydrate (P = 0.02) than plausible reporters. CONCLUSIONS Observed differences between under-reporters and plausible reporters suggest that the exclusion of these under-reporters represents an important potential source of bias in obesity research among women in the periconceptional period.