Chronotype and associations with dietary intake, meal timing, body composition, and metabolic biomarkers

In humans, meals are important non-photic zeitgebers for the circadian timing system, which is also influenced by chronotype. This study assessed whether chronotype is associated with dietary intake (energy; nutrients), meal timing, body composition markers, and metabolic biomarkers in healthy European and Pacific New Zealand (NZ) women.

Whole-body fat percentage (BF%), android-to-gynoid (AG) fat percentage ratio were assessed in 287 healthy non-pregnant European and Pacific NZ women aged 18-45 years using dual-energy X-ray absorptiometry (DXA). Body mass index (BMI) was calculated, and chronotype was assessed utilizing the Munich Chronotype Questionnaire (MCTQ). A 5-day estimated food record was used to assess dietary intake. Fasting venous blood samples were collected to evaluate metabolic biomarkers.

The majority of participants (54%) were classified as intermediate chronotypes (IT), 34% as evening types (ET), and 12% as morning types (MT). The ET group had higher BMI, BF%, and AG fat percentage ratio than the morning and intermediate-chronotypes groups (MT-IT): 31.4 vs. 26.1 kg/m², 36 vs. 34%, and 0.98 vs. 0.87, respectively. Daily energy intake was higher in ET than in MT-IT (p = 0.03). MT-IT had higher intakes of energy, protein, carbohydrate, and fat in the morning than ET (before 10:00); in contrast, ET had higher energy, protein, carbohydrate, and fat intakes in the evening after 20:00. The ET in high BF% and high AG ratio groups were more likely to have lower energy, protein, and carbohydrate intakes before 10:00 in the morning, as well as higher energy, carbohydrate, and fat intakes after 20:00. The ET group had overall a poorer lipid profile as well as glucose homeostasis than MT-IT (all p < 0.05).

The ET women consumed less energy and less micronutrient-dense food than the MT-IT. The ET had lower dietary intake in the morning but higher intake in the evening, with an inverse pattern observed among MT-IT. Higher energy and macronutrient intake in the evening was significantly associated with a higher BF% and AG ratio in ET, suggesting a potentially greater susceptibility to obesity.