This study investigated whether body fat percentage (BF%) in Japanese female university rhythmic gymnasts (RG) and non-athletes (control) was associated with the time-of-day of energy intake. A total of 57 females (RG group, n=34; control group, n=23) completed 24-h dietary recall surveys on 3 non-consecutive days. BF% was measured using a bioelectrical impedance analyzer after overnight fasting. Energy intake was stratified by time-of-day: morning (3:00 to 11:00), midday (11:00 to 17:00), evening (17:00 to 21:00), and nighttime (21:00 to 3:00). There was no significant difference between the groups in total energy intake, body weight, or body mass index. The RG group had significantly higher energy expenditure, a larger negative energy balance and lower BF% than the control group. The energy intake ratios (ER%) in the evening and at nighttime in the RG group were significantly lower and higher than in the control group, respectively. Total energy intake and energy balance did not show any significant association with BF% in either group. Multivariate linear regression with substitution model indicated that a substitution of ER% in the morning for ER% at nighttime was negatively associated with BF% after adjusting for confounding factors (β=-0.240; 95% confidence interval (CI): -0.455, -0.025) in the control group. In the RG group, a substitution of ER% in the evening for ER% at nighttime was negatively associated with BF% (β=-0.117; 95%CI: -0.214, -0.019). These results suggest that the timing of energy intake throughout the day is associated with BF% in Japanese university RG and non-athlete female students.
Keywords: 24-h dietary recall survey; body composition; energy intake ratio (ER%); substitution model; timing of energy intake.