The association among chronotype, timing of food intake and food preferences depends on body mass status.

BACKGROUND/OBJECTIVES
Previous studies have shown that individuals with circadian preferences for the evening (wake up later and reach maximum activity in the afternoon) have distorted dietary habits and misregulated body weight. Therefore, the present study was conducted to analyse the possible relationships between 'morningness' or 'eveningness' (chronotype), dietary habits and the level of obesity.

SUBJECTS/METHODS
Among 400 participants, 171 subjects finished the follow-up period and were evaluated. Anthropometric, clinical and dietary parameters were analysed; the Horne-Östberg test was used to determine chronotype. A hypocaloric-behavioural intervention was performed in the overweight/obese subjects.

RESULTS
In normal-weight subjects, the morningness group ingested most of their energy and nutrients at breakfast and lunch, whereas the eveningness group showed a higher intake at dinner, corresponding with their chronotypes. A significant interaction was revealed between chronotype and body mass index regarding the energy and nutrients consumed at dinner (P<0.05 in all cases), as in the normal-weight subjects the evening food intake was higher in the eveningness group, but in the overweight subjects the situation was inverse. In addition, the food preferences were related to the chronotype, as the morningness subjects showed a higher intake of fruit (P<0.010).

CONCLUSIONS
The timing of food intake corresponded to the chronotype in the normal-weight subjects; however, the overweight/obese subjects showed intake patterns removed from their physiological rhythms. These findings may indicate a need to design specific diets based not only on the total energy expenditure but also on the chronotype, as an indicator of the biological rhythms.European Journal of Clinical Nutrition advance online publication, 21 September 2016; doi:10.1038/ejcn.2016.182.