Are People Consuming the Diets They Say They Are? Self-Reported vs Estimated Adherence to Low-Carbohydrate and Low-Fat Diets: National Health and Nutrition Examination Survey, 2007-2018.

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 with their estimated adherence using up to 2 24-hour recalls.

DESIGN

This cross-sectional study acquired data on dietary intake from respondents in the National Health and Nutrition Examination Survey, 2007-2018.

PARTICIPANTS/SETTING: This study included 30 219 respondents aged 20 years and older 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 2 24-hour recalls and usual intake methodology developed by the National Cancer Institute.

RESULTS

Of the 1.4% of participants who reported following 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 value for difference = .014). Of the 2.0% of participants who reported following a low-fat diet, estimated adherence (<30% energy from fat) was 23.0%, whereas estimated adherence among those who did not report following a low-fat diet was 17.8% (P value for difference = .048).

CONCLUSIONS

This research demonstrates that most individuals mischaracterized their diet pattern when compared with up to 2 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.