Background As internet use becomes more widespread, the screen time (ST) of elementary school students increases yearly. It is known that longer durations of ST can affect obesity, physical activity, dry eye disease, and learning ability. However, the effects of ST just before bedtime have not been clarified. Therefore, we examined ST duration and timing effects on elementary school children. Methods We conducted a survey of 7419 elementary school students in Tokyo, Japan using a questionnaire on food education. ST duration and timing (just before bedtime) served as the explanatory variables, and the relationship between obesity, physical activity, dry eyes, and learning ability was analyzed using logistic regression analysis. Gender, school year, height, and weight were considered confounding factors. First, we examined whether ST duration and timing were related to each objective variable, using a univariate model to examine all variables. Thereafter, we performed multivariate logistic regression analyses for all variables showing a significant difference in the univariate models. Results A significant association was observed between ST duration and obesity, physical activity, and academic performance, indicating that a longer ST duration may lead to obesity, decreased physical activity, and decreased academic performance. ST timing was associated with obesity, dry eyes, and academic performance, and ST immediately before bedtime contributed to obesity, dry eyes, and reduced academic performance. Furthermore, the results of investigating the combined effect of ST duration and timing (immediately before bedtime) on these factors revealed that ST timing has a greater effect on dry eyes, and ST duration has a greater effect on academic performance. Conclusion Our findings indicate that ST in school children is related to obesity, physical activity, dry eyes, and learning ability, and they suggest that not only the duration but also the timing of ST is important.

BackgroundGlucose and lipid tolerance reportedly exhibit diurnal variations, being lower in the evening than in the morning. Therefore, the effects of exercise on glucose and blood lipid levels at different times of the day may differ. This study aimed to investigate the effects of short-term endurance exercise intervention in the morning versus late afternoon on 24-h blood glucose variability and blood lipid levels.MethodsTwelve healthy young men participated in a randomized crossover trial. The participants were assigned to morning (09:00–11:00) or late afternoon (16:00–18:00) endurance exercise for a week, consisting of supervised exercise sessions on Mondays, Wednesdays, and Fridays. In the morning and evening trials, the participants walked for 60 min on a treadmill at approximately 60% of maximal oxygen uptake (VO2max). Following a 2-week wash-out period, the participants performed the exercise training regimen at another time point. Continuous glucose monitoring was used to evaluate blood glucose fluctuations during each 24-h trial period. Blood samples were collected before and after each intervention to examine blood lipid and hormonal responses.ResultsExamination of the area under the curve (AUC) of the glucose level changes for 24 h after the late afternoon versus morning exercise intervention revealed significantly lower values for the former versus the latter (P < 0.01). The AUC of glucose level changes after each meal was also lower after the late afternoon versus morning intervention, and significantly lower values were observed in the late afternoon versus morning trial for breakfast and dinner (P < 0.05, P < 0.01). In addition, a significant decrease in triglycerides (TG) and TG/high-density lipoprotein cholesterol (HDL-C) was noted after versus before the late afternoon intervention (P < 0.05).ConclusionsThese results suggest that late afternoon endurance exercise is more effective than morning endurance exercise at improving 24-h glucose and triglyceride levels.

Highlights d Distribution of dietary protein across meals influences muscle hypertrophy d BCAAs are involved in hypertrophic effects of protein feeding distribution d Hypertrophic effects of protein feeding distribution require the muscle clock d Breakfast protein intake is correlated with skeletal muscle functions in older women

To date, nutritional studies have focused on the total intake of dietary fiber rather than intake timing. In this study, we examined the effect of the timing of daily Helianthus tuberosus ingestion on postprandial and 24 h glucose levels, as well as on intestinal microbiota in older adults. In total, 37 healthy older adults (age = 74.9 ± 0.8 years) were recruited. The participants were randomly assigned to either a morning group (MG, n = 18) or an evening group (EG, n = 17). The MG and EG groups were instructed to take Helianthus tuberosus powder (5 g/day) just before breakfast or dinner, respectively, for 1 week after the 1-week control period. The glucose levels of all participants were monitored using a continuous glucose monitoring system throughout the 2 weeks. The intestinal microbiota was analyzed by sequencing 16S rRNA genes from feces before and after the intervention. There were no significant differences in the physical characteristics or energy intake between groups. Helianthus tuberosus intake led to decreases in tissue glucose levels throughout the day in both groups (p < 0.01, respectively). As a result of examining the fluctuations in tissue glucose levels up to 4 hours after each meal, significant decreases in the areas under the curves (AUCs) were observed for all three meals after intervention, but only in the MG (breakfast: p = 0.012, lunch: p = 0.002, dinner: p = 0.005). On the other hand, in the EG, there was a strong decrease in the AUC after dinner, but only slight decreases after breakfast and lunch (breakfast: p = 0.017, lunch: p = 0.427, dinner: p = 0.002). Moreover, the rate of change in the peak tissue glucose level at breakfast was significantly decreased in the MG compared to the EG (p = 0.027). A greater decrease was observed in the change in the blood glucose level after the ingestion of Helianthus tuberosus in the MG than in the EG. Furthermore, the relative abundance of Ruminococcus in the MG at the genus level was significantly higher at baseline than in the EG (p = 0.016) and it was also significantly lower after the intervention (p = 0.013). Our findings indicate that Helianthus tuberosus intake in the morning might have relatively stronger effects on the intestinal microbiota and suppress postprandial glucose levels to a greater extent than when taken in the evening.

To examine the effects of the intake of a snack containing dietary fiber under free-living conditions on postprandial glucose levels in older adults, nine healthy older adults aged 76.9 ± 1.6 years (mean ± standard error) completed two crossover trials: 1) regular snack (BISCUIT) intake and 2) intake of snacks with a high dietary fiber content (DF-BISCUIT). In both trials, each participant consumed either BISCUIT or DF-BISCUIT between lunch and dinner time for 1 week. During the intervention, the blood glucose levels of all the subjects were observed using a continuous glucose monitoring system. Lower 24 h blood glucose levels were yielded in the DF-BISCUIT than the BISCUIT trials. Moreover, compared to the BISCUIT trials, the blood glucose levels after dinner and areas under the curve (AUCs) were significantly decreased in the DF-BISCUIT treatments. The blood glucose levels and AUCs after the intake of the next day’s breakfast were suppressed in the DF-BISCUIT treatments compared to those in the BISCUIT trials. Our data indicate that the intake of snacks with a high dietary fiber content under free-living conditions is an effective way to restrain postprandial glucose levels and that the effect lasts until breakfast the next day.