Amirhossein Yazdinezhad - Student Research Committee. Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Moslem Askarpour - Student Research Committee. Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Mohammad Mehdi Aboushamsia - Student Research Committee. Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Maryam Asadi - Nutrition and Metabolic Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Anahita Mansoori - Nutrition and Metabolic Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

Background and Objective: Recent studies have shown a relationship between energy regulation and the circadian rhythm at behavioral, molecular, and physiological levels. The present study investigated the effect of chronotype on meal timing and obesity in Iranian housewives. Materials and Methods: This cross-sectional study was carried out using a convenience-sampling method through the participation of housewives living in Ahvaz in ۲۰۱۸. Anthropometric information was collected. To assess food intake timing, energy intake and sleep patterns during seven days of normal living were recorded by the researchers. Dietary information was obtained by using a ۲۴-hour recall questionnaire and analyzed by NUT IV software. The morningness-eveningness questionnaire (MEQ) was used to determine chronotypes. Results: There was a significant difference between the morning and evening groups in terms of the timing of lunch (P=۰.۰۰۴) and mid-afternoon snacks (P=۰.۰۴). There was no significant difference between mean energy intake in the morning and evening chronotypes in women who were overweight or obese (P=۰.۳۱). There was also no significant difference between morning and evening chronotypes in terms of the percentage of energy intake of meals and snacks (P>۰.۰۵). The only significant difference, detected between morning and evening chronotypes in normal-weight women, was for the percentage of energy intake after ۳:۰۰ PM. (P=۰.۰۰۸). Conclusion: The present study showed no effect of chronotype on obesity. However, energy intake calculations were based on self-reports, which could lead to information bias. Therefore, in future studies, researchers should carry out clinical trials while controlling food intake and considering meal timing.

Chronotype, Energy regulation, Obesity, Meal timing, Sleep patterns