Intake Differences between Subsequent 24-h Dietary Recalls Create Significant Reporting Bias in Adults with Obesity

In depth understanding of the dietary patterns of individuals with obesity is needed in practice and research, in order to support dietitians and physicians in the design and implementation of nutritional management. We aimed to analyze the consistency of energy, macro-, and micronutrient reported intakes in four non-consecutive 24-h dietary recalls from 388 adults with obesity using information collected in the NutriGen Study (ClinicalTrials.gov, NCT02837367). Significant decreases were identified for reported energy and several, macro- and micronutrient intakes, between the first and subsequent 24-h recalls. Significant differences of reported intakes were identified in sensitivity analyses, suggesting that the first recall (also the only one performed on site, face-to-face) might be a point of bias. A comparison of the differences in intakes between weekend and weekday, after adjustment for false discovery rate were non-statistically significant either in male, females, or in total. To overcome this potential bias, studies should be carefully conducted, starting from the design phase, through to the analysis and interpretation phases of the study. Prior to averaging specific intakes across all sessions of reporting, a preliminary analysis must be conducted to identify if a certain time point had significant differences from all other time points and overview potential sources of bias: reporting bias, training bias, or behavioral changes could be responsible for such differences.