Few studies have described the status and change of time-of-day of energy intake on a population level. This study aims to investigate the secular trend in time-of-day of energy intake using a Chinese cohort, and to examine demographic disparities in trends. A total of 20,976 adults with at least two waves of dietary data in the China Health and Nutrition Survey (CHNS 1991-2018) were included. A multilevel linear mixed model was applied to the energy proportions of breakfast, lunch and dinner. A multilevel Tobit regression model was applied to the energy proportion of morning snack, afternoon snack and evening snack. Time-demographic interaction terms were tested to examine demographic disparities in the trends. From 1991 to 2018, the marginal mean of the energy proportion of breakfast experienced first a falling and then a rising trend, and the marginal mean of energy proportions of lunch and dinner both presented first a rising and then a falling trend. The marginal means of all snacks took on a rising trend. Significant time-demographic interactions were observed for energy proportion of each eating occasion. On average, female, older and rural people tended to have a higher energy proportion at breakfast and lower energy proportion at lunch and dinner. Female, younger and urban people tended to have higher snack energy proportions. The time-of-day of energy intake has first shifted towards later in the day and then towards a balanced meal pattern in this Chinese cohort. Demographic disparities were observed in both the secular trend and the mean level of energy proportions of eating occasions. The health implications of such meal patterns warrant further investigation.
Keywords: cohort; energy intake; snacking; time-of-day; trend.