Are people consuming the diets they say they are? Self-reported versus estimated adherence to low carbohydrate and low fat diets: National Health and Nutrition Examination Survey, 2007-2018.

ABSTRACT

BACKGROUND: Mischaracterization of dietary intake by patients and study participants is a common problem that presents challenges to clinical and public health approaches to improve diet quality, identify healthy eating patterns, and reduce the risk of chronic disease. OBJECTIVE: This study examined participants' self-reported adherence to low carbohydrate and low fat diets compared to their estimated adherence using up to two 24-hour recalls. DESIGN: This cross-sectional study acquired data on dietary intake from respondents in the National Health and Nutrition Examination Survey (NHANES) 2007-2018. PARTICIPANTS/SETTING: This study included 30,219 respondents ≥20 y who had complete and reliable dietary data and were not pregnant or breastfeeding. MAIN OUTCOME MEASURES: The main outcome was prevalence of self-reported and estimated adherence to low carbohydrate or low fat diet patterns. STATISTICAL ANALYSES PERFORMED Self-reported adherence to low carbohydrate or low fat diets was evaluated using responses to questionnaires. Estimated adherence to these diets was assessed using data from up to two 24-hour recalls and usual intake methodology developed by the National Cancer Institute. RESULTS: Of the 1.4% of participants that reported being on a low carbohydrate diet, estimated adherence (<26% energy from carbohydrates) using 24-hour recalls was 4.1%, whereas estimated adherence among those that did not report following a low carbohydrate diet was <1% (P-difference=0.014). Of the 2.0% of participants who reported being on a low fat diet, estimated adherence (<30% energy from fat) was 23.0%, whereas estimated adherence among those that did not report following a low fat diet was 17.8% (P-difference=0.048). CONCLUSIONS: This research demonstrates that most individuals mischaracterized their diet pattern when compared to up to two 24-hour recalls. These findings emphasize the need for clinicians and public health professionals to be cautious when interpreting individuals' self-reported diet patterns, and should aim to collect more detailed dietary data when possible.