Time-of-Day of Energy Intake Is Associated with Body Fat Percentage in Japanese Female University Rhythmic Gymnasts and Non-Athlete Students.

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 (ß=-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% (ß=-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.

Habitual dietary protein intake affects body iron status in Japanese female college rhythmic gymnasts: a follow-up study.

BACKGROUND: Many rhythmic gymnasts stay lean by reducing their body weight (BW); however, this may result in iron deficiency (ID). Our previous cross-sectional study reported an association between ID incidence and protein intake in gymnasts during the pre-season. The present study aimed to examine the association between dietary protein intake and ID incidence in a 2-year follow-up study. METHODS: Elite Japanese female college rhythmic gymnasts [mean age ± standard deviation (SD): 18.4 ± 0.5 years] were recruited on a voluntary basis every August for 9 years. Anthropometric, dietary intake, and hematological parameters were measured at baseline and 2 years later. A total of 20 participants without ID at baseline were divided into either a lower (L, n = 11) or higher (H, n = 9) protein group based on median protein intake (1.3 g protein/kg BW). RESULTS: Participants consumed 1.08 ± 0.16 and 1.55 ± 0.14 g/kg BW of protein in the L and H groups, respectively. No significant changes in the intake of protein and other nutrients were observed between baseline and 2-year follow-up in both groups. ID was observed in a total of eight (72.8 %) participants in the L group and one (11.2 %) in the H group at follow-up. The incidence of ID was significantly lower in the H group than the L group (Fisher's exact test, odds ratio, 0.043; 95 % CI 0.004-0.552; p = 0.010). CONCLUSIONS: During the pre-season weight loss period, habitually higher protein intake may reduce ID incidence among elite college female rhythmic gymnasts.

Relationship Between Dietary Factors and Bodily Iron Status Among Japanese Collegiate Elite Female Rhythmic Gymnasts.

This cross-sectional study explored the prevalence of iron deficiency (ID) and associations between dietary factors and incidence of ID in female rhythmic gymnasts during preseason periods. Participants were 60 elite collegiate rhythmic gymnasts (18.1 ± 0.3 years [M ± SD]) who were recruited every August over the course of 8 years. Participants were divided into 2 groups according to the presence or absence of ID. Presence of ID was defined either by ferritin less than 12 µg/L or percentage of transferrin saturation less than 16%. Anthropometric and hematologic data, as well as dietary intake, which was estimated via a semiquantitative food frequency questionnaire, were compared. ID was noted in 48.3% of participants. No significant group-dependent differences were observed in physical characteristics, red blood cell counts, hemoglobin, hematocrit, haptoglobin, or erythropoietin concentrations. The ID group had a significantly lower total iron-binding capacity; serum-free iron; percentage of transferrin saturation; ferritin; and intake of protein, fat, zinc, vitamin B2, vitamin B6, beans, and eggs but not iron or vitamin C. The recommended dietary allowance for intake of protein, iron, zinc, and various vitamins was not met by 30%, 90%, 70%, and 22%-87% of all participants, respectively. Multiple logistic analysis showed that protein intake was significantly associated with the incidence of ID (odds ratio = 0.814, 95% confidence interval [0.669, 0.990], p = .039). Participants in the preseason's weight-loss periods showed a tendency toward insufficient nutrient intake and were at a high risk for ID, particularly because of lower protein intake.