Background/objectives: Healthy eating advice is informed, in part, by dietary surveys that rely on self-reported data. Misreporting of food intake may distort relationships between diet and health outcomes. This study directly quantified the food groups that were under-reported or over-reported in common dietary assessment techniques.
Subjects/methods: Food and drink consumption of 59 adults, with ad libitum access to a range of familiar foods, was objectively and covertly measured by investigators, and validated against independent measures of energy balance, while participants were resident in the Human Nutrition Unit of the Rowett Institute. Participants self-reported their diets using weighed dietary records (WDR) and multiple-pass 24-hr recalls over two periods of 3 days using a cross-over design. Foods and drinks were aggregated into 41 food groups.
Results: The mean daily weight of food and drinks reported was significantly lower than actually consumed; 3.3 kg (p = 0.004, 95% confidence interval (CI) = 3.07-3.55 kg) and 3.0 kg (p < 0.001, CI = 2.80-3.15 kg) for the WDR and 24-hr recall respectively, compared with 3.6 kg for the objective measure. Reported intakes were significantly lower than the objective measure for four and eight food groups (WDR and 24 h recall, respectively), and not significantly different for the remaining food groups.
Conclusions: Although under-reporting was greater for some food groups than for others, 'healthy' foods were not over-reported and 'unhealthy' foods were not consistently under-reported. A better understanding of which foods tend to be misreported could lead to improvements in the methods of self-reported dietary intakes.