Objective: This study describes patterns of bias in self-reported dietary recall data of girls by examining differences among girls classified as under-reporters, plausible reporters, and over-reporters on weight, dietary patterns, and psychosocial characteristics.
Research methods and procedures: Participants included 176 girls at age 11 and their parents. Girls' weight and height were measured. Three 24-hour dietary recalls and responses to psychosocial measures were collected. Plausibility cut-offs for reported energy intake as a percentage of predicted energy requirements were used to divide the sample into under-reporters, plausible reporters, and over-reporters. Differences among these three groups on dietary and psychosocial variables were assessed to examine possible sources of bias in reporting.
Results: Using a +/-1 standard deviation cut-off for energy intake plausibility, 50% of the sample was categorized as plausible reporters, 34% as under-reporters, and 16% as over-reporters. Weight status of under-reporters was significantly higher than that of plausible reporters and over-reporters. With respect to reported dietary intake, under-reporters were no different from plausible reporters on intakes of foods with higher nutrient densities and lower energy densities and were significantly lower than plausible reporters on intakes of foods with lower nutrient densities and higher energy densities. Over-reporters reported significantly higher intakes of all food groups and the majority of subgroups, relative to plausible reporters. Under-reporters had significantly higher levels of weight concern and dietary restraint than both plausible reporters and over-reporters.
Discussion: Techniques to categorize plausible and implausible reporters can and should be used to provide an improved understanding of the nature of error in children's dietary intake data and account for this error in analysis and interpretation.