Table 6.

Methodological recommendations for future observational studies

Design	Long-term longitudinal studies
Sample characteristics	Population-based studies with representative samples and sample size to perform analysis by sex
Exposure assessment	Accurate methods should be used for data collection, such as recalls and food diaries, or standardized pattern of meal questionnaires, which can measure food habits; and misreporting should be taken into account in the analyses It is necessary to standardize the method of classifying the eating occasion (main meal and snacks) in order to use a reproducible method between studies The analysis should compare the intake of the three major meals (breakfast, lunch and dinner) with a greater number of meals, in order to propose health recommendations based on results
Outcome assessment	Anthropometric measurements of weight, height to determine BMI, as well as abdominal adiposity measurements (waist, abdominal and hip circumferences), should be obtained using standard techniques, avoiding using self-reported measures, especially in cross-sectional studies In addition to BMI and abdominal adiposity, measures of body composition should be included, such as fat mass and fat-free mass, in order to understand the role of eating frequency on body composition. Body composition should be evaluated by objective measurements, such as dual-energy X-ray absorptiometry, impedance or densitometry, when it is possible
Confounders and mediators	The analyses should be stratified by sex, if the sample size allows for this, in order to explore whether there are differences in the association between eating frequency and adiposity according to sex Should apply multivariate analyses or other statistical methods to control for possible confounding, such as by age, education, race/ethnicity, marital status, income, physical activity, smoking and sleep duration When associations between eating frequency and body weight or body composition are found, it is very important to investigate the role of food habits, with special attention to energy intake, quality of diet, meal composition (macro- and micronutrients) and meal timing as mediator factors. Furthermore, they should be appropriately measured and under-reporting bias should be taken in account