Refereed, Nutrition and health, The differential impact of gaze direction on food evaluation., Kenichi Shibuya; Mana Miyamoto, Background: The influence of others' gaze on human behavior remains incompletely understood. However, it remains unclear whether direct gaze actively enhances evaluation. Aim: The primary aim of this study was to investigate whether direct gaze increases the evaluation of food items. Methods: To address this gap, we conducted an experiment in which 29 Japanese participants (aged 19-22; 6 males) evaluated food images paired with facial images displaying either direct or averted gaze. Using a 9-point Likert scale, participants rated the attractiveness of 12 food items under each gaze condition. Results: Statistical analysis via linear mixed models revealed that food was rated significantly higher when accompanied by direct gaze compared to averted gaze (Estimate = 0.303, p = 0.008; 95% CI: 0.078-0.528). These findings support the hypothesis that direct gaze enhances positive evaluation, possibly through mechanisms such as reputation management, increased arousal, and social facilitation. Conclusion: Our results contribute to a growing body of literature on social influences in perception and suggest that subtle social cues can modulate sensory evaluations. Future research should incorporate dynamic or immersive stimuli, assess physiological responses, and explore cross-cultural differences to clarify the underlying mechanisms. These efforts will deepen our understanding of how gaze direction shapes food perception and may inform applications in marketing, health communication, and user experience design., 24 Jul. 2025, 31, 4, 2601060251362331, 2601060251362331, Scientific journal, True, 10.1177/02601060251362331

Refereed, PeerJ, Exploring the impact of visual stimuli on taste expectations and the role of pull-tab position in food packaging., Kenichi Shibuya; Mana Miyamoto, BACKGROUND: Preference for an image is often associated with the perceived ease of use of the depicted object. AIM: This study investigated the impact of visual stimuli on taste expectations, focusing on the presentation of food in images. Specifically, it explored how the presence of a pull-tab-perceived by participants as a tool that makes the product easy to use or open-influences these expectations. METHODS: A sample of 42 right-handed university students (30 women, 12 men; mean age = 20.4 years) evaluated perceived taste expectations of food presented under different conditions using a 9-point Likert scale. The conditions included images of canned food ("Can condition") with varying pull-tab positions (0°, 90°, 180°, 270°, and Down), as well as images of actual food ("Pineapple condition"). Each participant was shown 12 images per trial in a randomized order and rated their taste expectations immediately after viewing each image. Statistical analyses were conducted using linear mixed models and ANOVA using the Kenward-Roger method. RESULTS: Taste expectations were significantly lower in the Can condition compared with the Pineapple condition (mean difference = 3.14, SE = 0.23, p < 0.001). Within the Can condition, pull-tab positions had a significant effect on taste expectation ratings (F = 116.94, p < 0.001). The 0° position (pull-tab facing the viewer) received the highest rating (M = 4.87, SD = 1.86), while the 180° position (pull-tab facing away) received the lowest (M = 3.95, SD = 1.73). CONCLUSION: These findings underscore the complex relationship between visual presentation and taste expectations, providing valuable insights for optimizing product presentation in marketing strategies., 2025, 13, e20417, Scientific journal, True, 10.7717/peerj.20417

Refereed, Nutrition and Health, SAGE Publications, Preliminary findings on the influence of the presence of others’ eyes on food intake, Risa Santa; Mana Miyamoto; Kenichi Shibuya, Background: The presence of others’ eyes has been shown to influence food evaluation. Aim: The purpose of the present study was to investigate whether the presence of others’ gaze would lead to a reduction in food intake in accordance with social norms. Methods: In this study, we enlisted the participation of 30 volunteers. During the experiment, participants had the opportunity to consume noodles freely as much as they wanted while viewing one of the three images: (1) featuring a person with open eyes (Open condition), (2) depicting a person with closed eyes (Closed condition), and (3) displaying an image devoid of a person (None condition). Results: Food consumption in each condition was 460.00 ± 20.97 g for the Open condition, 515.57 ± 22.97 g in the Closed condition, and 505.03 ± 21.05 g in None condition. The condition had a statistically significant main effect ( F = 4.656, p = .013). The Least-Square means analysis revealed that food consumption in the Open condition was significantly lower than in the other two conditions (Closed and None conditions) (Closed − Open: t = 2.872 [95% CI: 16.844–94.289], p = .006; None – Open: t = 2.328 [95% CI: 6.311–83.756], p = .023). There was no significant difference in food consumption between the Closed and None conditions (Closed − None: t = 0.545 [95% CI: −28.189–49.256], p = .588). Conclusion: The results of the present study suggest that the presence of others’ eyes would reduce food intake in accordance with social norms., 2025, 31, 3, 1189, 1194, Scientific journal, True, 10.1177/02601060241282941

Refereed, International Journal of Gastronomy and Food Science, Elsevier BV, Exploring the influence of user-friendly cutlery on the food consumption levels, Kenichi Shibuya; Risa Santa; Mana Miyamoto, Jun. 2024, 36, 100935, 100935, Scientific journal, 10.1016/j.ijgfs.2024.100935

Refereed, PeerJ, Sleep duration has a limited impact on the prevalence of menstrual irregularities in athletes: a cross-sectional study., Mana Miyamoto; Kenichi Shibuya, BACKGROUND: This study aimed to investigate the relationship between the prevalence of menstrual irregularities, energy intake, and sleep deprivation among female athletes. METHODS: A total of 128 female athletes, with an average age of 19.2 ± 1.2 years, participated in the study and tracked their food intake over a three-day period. Menstrual status and sleep duration were assessed using a questionnaire, and psychological anxiety was evaluated using the State and Trait Anxiety Inventory (STAI). These were measured once during the investigation. The impact of sleep status on state anxiety and daily energy intake was examined using the T-test. A generalized linear model (GLM) with a log link function was employed to investigate the effects of sleep deprivation on the presence of menstrual irregularities. RESULTS: As the results of the present study, sleep deprivation significant increased both state and trait anxiety (p < 0.05), as well as affecting energy intake (p < 0.05), particularly protein and carbohydrate intakes (p < 0.05). However, GLM analysis indicated that while sleep deprivation did not directly influence the prevalence of menstrual irregularities (p > 0.05), state anxiety emerged as a significant factor impacting the prevalence of menstrual irregularities (p < 0.05). CONCLUSIONS: The results of the present study suggest a potential pathway wherein sleep deprivation might elevate state anxiety levels, consequently indirectly contributing to an increase the probability of menstrual irregularities. In conclusion, the results of the presents study provide novels insights suggesting that sleep deprivation might directly increase state anxiety and indirectly affect the prevalence of menstrual irregularities. Hence, decreased sleep duration might be related to mental health issues and the prevalence of menstrual irregularities both significant concerns among female athletes. Future studies will play a crucial role in further elucidating how sleep patterns impact the health and well-being of female athletes., 2024, 12, e16976, Scientific journal, True, 10.7717/peerj.16976

Refereed, PeerJ, Exploring the relationship between nutritional intake and menstrual cycle in elite female athletes, Mana Miyamoto; Kenichi Shibuya, This study aimed to examine potential variations in nutritional intake among female athletes, including top-level, throughout the menstrual cycle. A total 122 female athletes participated in the study, documenting their food consumption over a 3-day period. The menstrual status of female athletes was also assessed, and using the survey results, the phase of the menstrual cycle (the follicular, early luteal, or late luteal) during which each meal was recorded was determined. Consequently, the meal records were categorized into the respective three phases. The findings of this study indicated that there were no notable disparities in nutritional intake, encompassing energy, protein, fat, carbohydrate, calcium, iron, and fiber, across the three phases of the menstrual cycle. The results imply that female athletes may experience comparatively smaller variations in nutrient intake related to the menstrual cycle. This could be attributed to the higher energy requirements of female athletes because of their rigorous training. This study underscores the significance of accounting for the population when examining nutrient intake changes associated with the menstrual cycle., Sep. 2023, 11, e16108, Scientific journal, True, 10.7717/peerj.16108

Refereed, Journal of Texture Studies, Wiley, Effects of different food hardness on cognitive inhibitory control function, Suzuha Kidoura; Yumeno Higuchi; Naoto Sato; Risa Santa; Mana Miyamoto; Kenichi Shibuya, Abstract

Mastication leads to an immediate enhancement in cognitive functions, including inhibitory control. Furthermore, the hardness of the food increases sympathetic nerve activity during and immediately after mastication. Hence, the cognitive function could be enhanced by increased sympathetic nerve activity. The present study aimed to investigate the effects of food hardness on cognitive inhibitory control function in humans. The participants were 23 healthy adults (19–22 years old). Experiments were conducted with two types of gummies (soft and hard). The participants ingested 13 g of gummies and performed a stop‐signal task to measure cognitive inhibitory control function after they rested for 5 min. The reaction time for the stop‐signal task after gummy consumption was significantly shorter in the hard gummy condition compared to the soft gummy condition (p < .05). Furthermore, the accuracy rate of the responses was also significantly higher in the hard gummy condition compared to the soft gummy condition (p < .05). The results of the present study suggest that food hardness enhances cognitive inhibitory control function in humans., 09 Aug. 2023, 54, 6, 958, 962, Scientific journal, True, 10.1111/jtxs.12794

Refereed, Nutrition and Health, SAGE Publications, The effect of background music tempo on eating speed and food intake volume within in healthy women, Naoto Sato; Mana Miyamoto; Risa Santa; Chihiro Homma; Kenichi Shibuya, Background

The effects of the different tempos of background music (BGM) on food intake and eating speed have not been fully studied.

Aim

The study aimed to investigate the influence of changing the tempo of BGM during meals on food intake and to explore strategies to support appropriate eating behavior.

Methods

Twenty-six healthy young adult women participated in this study. In the experimental phase, each participant ate a meal under three separate conditions: fast (120% speed), moderate (original, 100% speed), and slow (80% speed) BGM. The same music was used for each condition, and appetite before and after eating, the amount of food consumed, and eating speed were recorded.

Results

The results showed that food intake (g, mean ± standard error (SE)) was slow: 317.9 ± 22.2, moderate: 400.7 ± 16.0, and fast: 342.9 ± 22.0. Eating speed (g/s, mean ± SE) was slow: 28.1 ± 2.8, moderate: 34.2 ± 2.7, and fast: 27.2 ± 2.4. The analysis showed that the moderate condition showed greater speed than the fast and slow conditions (slow–fast: p = .008; moderate–slow: p = .012; moderate–fast: p = .004). Moreover, the food intake in the moderate condition was significantly higher than that in the slow and fast conditions (moderate–slow: p < .001; moderate–fast: p < .001), and there was no significant difference between the slow and fast conditions in this regard ( p = .077).

Conclusion

These results suggest that original tempo BGM led to higher food intake compared to the faster and slower tempo conditions. These findings suggest that listening to music at an original tempo during meals may support appropriate eating behavior., 19 Feb. 2023, 026010602311582, 026010602311582, Scientific journal, True, 10.1177/02601060231158234

Refereed, PeerJ, PeerJ, Cross-modal and subliminal effects of smell and color, Naoto Sato; Mana Miyamoto; Risa Santa; Ayaka Sasaki; Kenichi Shibuya, In the present study, we examined whether the cross-modal effect can be obtained between odors and colors, which has been confirmed under olfactory recognizable conditions and also occurs under unrecognizable conditions. We used two flavors of red fruits such as strawberries and tomatoes for this purpose. We also aimed to compare whether similar cross-modal effects could be achieved by setting the flavors at recognizable (liminal) and unrecognizable (subliminal) concentrations in the experiment. One flavor at a normal concentration (0.1%, Liminal condition) and one at a concentration below the subliminal threshold (0.015%, Subliminal condition), were presented, and the color that resembled the smell most closely from among the 10 colors, was selected by participants. Except for the subliminal tomato condition, each odor was significantly associated with at least one color (p < 0.01). Participants selected pink and red for liminal strawberry (0.1%) (p < 0.05), pink for subliminal strawberry (0.015%) (p < 0.05), and orange for liminal tomato (0.1%) (p < 0.05), but there was no color selected for subliminal tomato (0.015%) (p < 0.05). The results of this study suggest that the flavor of tomato produced a cross-modal effect in liminal conditions, but not in subliminal conditions. On the other hand, the results of the present study suggest that the flavor of strawberries produces a cross-modal effect even under subliminal conditions. This study showed that cross-modal effects might exist, even at unrecognizable levels of flavor., 17 Feb. 2023, 11, e14874, e14874, Scientific journal, True, 10.7717/peerj.14874

Refereed, 2023, 9, 5, 10, Research institution, 5-10　体型判断におけるベイズ統合の影響.pdf, False

Refereed, PeerJ, PeerJ, Increased vitamin D intake may reduce psychological anxiety and the incidence of menstrual irregularities in female athletes, Mana Miyamoto; Yuko Hanatani; Kenichi Shibuya, Background

Vitamin D deficiency has been associated with major depression and premenstrual mood symptoms, and menstrual irregularity has been correlated with mental anxiety. However, the potential effect of increased vitamin D intake on reducing the risk of menstrual irregularities by decreasing psychological anxiety is yet to be fully elucidated. The existence of such a relationship in athletes with high levels of psychological anxiety and adequate dietary intake remains unknown. Therefore, this study aimed to examine the effects of vitamin D intake on psychological anxiety levels and the risk of menstrual irregularities in healthy college-and international-level female athletes.

Methods

Female intercollege-level track and field and international-level rowing athletes (n = 107) aged 15–24 years were included in this study. Their nutritional intake, body mass, body fat, mental anxiety, and menstrual irregularities were investigated. A generalized linear mixed model (GLMM) was used to examine the effects of several parameters on menstrual irregularities. The independent variables introduced into the GLMM were determined based on Akaike’s information criterion.

Results

The GLMM identified a significant interaction effect of vitamin D intake and state anxiety on menstrual irregularities, with a p-value of 0.049 and an odds ratio of 0.423. The study results suggest that increased vitamin D intake in relatively young endurance athletes may reduce mental anxiety, consequently decreasing menstrual irregularities., 21 Nov. 2022, 10, e14456, e14456, Scientific journal, True, 10.7717/peerj.14456

Refereed, Food Quality and Preference, Preliminary findings: Preferences of right-handed people for food images oriented to the left vs. right side., Kenichi Shibuya; Rina Kasuga; Naoto Sato; Risa Santa; Chihiro Homma; Mana Miyamoto, 2022, 97, 104502, Scientific journal, 10.1016/j.foodqual.2021.104502

Refereed, Nutrients, MDPI AG, Relationship among Nutritional Intake, Anxiety, and Menstrual Irregularity in Elite Rowers, Mana Miyamoto; Yuko Hanatani; Kenichi Shibuya, There is evidence showing that excessive mental stress is detrimental to the menstrual period, and it is known that many elite athletes are highly susceptible to mental anxiety. This study investigated the nutritional intake and mental anxiety of 104 relatively young elite endurance athletes aged 16 to 23 years and used a multiple logistic model to examine the factors that might be related to menstrual irregularity. Calcium intake was marginally associated with the occurrence of menstrual irregularities (odds ratio = 1.004, p = 0.030), whereas there were strong associations between body mass or state anxiety and menstrual irregularities in elite athletes (odds ratio = 0.557, p = 0.035 for body mass; odds ratio = 1.094, p = 0.006 for state anxiety). These results suggested that state anxiety would be an important factor causing menstrual irregularity in elite endurance athletes. It is recommended that elite athletes are monitored for anxiety levels and develop a strategy for stress management., 28 Sep. 2021, 13, 10, 3436, 3436, Scientific journal, True, 10.3390/nu13103436

Refereed, The Journal of Sports Medicine and Physical Fitness, Edizioni Minerva Medica, Dietary intake and menstrual cycle changes in international level young athletes, Mana MIYAMOTO; Yuko HANATANI; Kenichi SHIBUYA, BACKGROUND: Few studies have examined the influence of nutritional status and mental stress on menstrual cycle characteristics. The purpose of this study was to describe the impact of low energy availability (EA) and mental health problems on the menstrual cycles of elite female rowing competitors during a survey period. METHODS: We enrolled sixteen subjects (16-18 years old) who were elite female rowing competitors preparing for an international competition. This study provides the first long-term assessment of dietary intake, body mass/composition, state of anxiety, and menstrual cycle in international level female athletes. RESULTS: Dietary energy intake increased significantly during the investigation period (P<0.001). CHO intake increased significantly during the investigation period (P<0.005). EA significantly increased during the investigation period (P<0.01). The percentage of athletes with menstrual dysfunction was 20.0% in April 2018 (2 of 10), but none of the athletes reported menstrual dysfunction in October 2019. The mental status measured by state anxiety index (STAI) did not change significantly during this survey period (P>0.05). CONCLUSIONS: There was no athlete who has menstrual disfunction after sufficient CHO intake during this survey period. These findings of this study suggest that adequate EA levels and sufficient CHO intake might lead to improved menstrual function. In addition, the impact of psychological factors on menstrual dysfunction at normal levels may be less than the effects of nutritional status., Jun. 2021, 61, 6, 851, 856, Scientific journal, True, 10.23736/s0022-4707.20.11392-6

Refereed, PeerJ, The effect of an image of watchful eyes on the evaluation of the appearance of food., Kenichi Shibuya; Mana Miyamoto; Risa Santa; Chihiro Homma; Sumire Hosono; Naoto Sato, It is known that an eye-like image promotes generosity. It is also known that the evaluation of the visual deliciousness of food is improved in the presence of an emotionally positive stimulus. The purpose of the present study was to examine whether the presence of open eyes (OPEN) causes generous behavior altering the evaluation of the visual deliciousness of food, and how the images of open and closed eyes (CLOSED) affect human emotions. Seventeen women participated in the present study. A picture of food was presented on a computer screen, and the participants predicted and evaluated its visual deliciousness. An image of OPEN or that of CLOSED was presented simultaneously with a picture of food. There was a significant difference between the OPEN and CLOSED conditions, as demonstrated by the scores on a nine-point Likert scale for visual deliciousness; the ratings in the OPEN condition were significantly higher than those in the CLOSED condition (p = 0.004). There was no significant difference in the image of watchful eyes for the perceived relaxation state; the ratings in the OPEN condition were not significantly higher than those in the CLOSED condition (p = 0.716). The results of the present study revealed that the evaluation of the visual deliciousness of food based on its appearance was likely due to the presence of an image of open watchful eyes, increasing the perceived visual deliciousness of the food without any changes in the participants' emotions., 2020, 8, e9804, Scientific journal, True, 10.7717/peerj.9804

Refereed, Journal of Nutritional Science and Vitaminology, Mastication of hard gumi can alter the gustatory threshold for sodium chloride, Risa Santa; Mana Miyamaoto; Natsuko Hosono; Mizuki Hoshi; Chihiro Homma; Aya Goto; Naoto Sato; Kasumi Suzuki; Hiromi Inaba; Kenichi Shibuya, In recent years, there has been an increase in the number of hypertensive diseases and the various diseases associated with them. A major cause of these is excessive salt intake. The purpose of the present study was to examine whether chewing hard foods lowers the saltiness threshold. Fifteen subjects (fourteen women and one man) participated in the present study. Two types of gummies are available as ingredients: hard and soft gummies. The saltiness thresholds before and after chewing of each gummi were studied using 11 different NaCl solutions. Then, points of subjective equality (PSEs) were calculated to detect changes in the saltiness for each subject. In the soft Gumi condition, there was no significant difference in PSE for the saltiness between before and after ingesting Gumi (p>0.05), while in the hard Gumi condition, the PSE for the saltiness significantly decreased after ingesting Gumi compared with the value of before ingesting Gumi (p=0.001). From these results, we concluded that sensitivity to saltiness would increase after mastication of hard foods such as hard Gumi., 2020, 66, 6, 587, 590, Scientific journal, False, 10.3177/jnsv.66.587

Refereed, Journal of Human Ergology, Yellow dishes increase the perception of the overall-liking of popcorn, Mana Miyamoto; Riko Sakaue; Naoto Sato; Kasumi Suzuki; Kenichi Shibuya, 2020, 49, 9, 15, Scientific journal, 10.11183/jhe.49.1_17

Refereed, Journal of Human Ergology, Non-caloric sweeter enhances oxygenation of the prefrontal cortex after gum chewing, Mana Miyamoto; Naomi Kuboyama; Naoto Sato; Kenichi Shibuya, 2020, 49, 17, 23, Scientific journal

Refereed, Journal of Human Ergology, Complementary activation in the ipsilateral to the contralateral primary motor cortex during high-intensity exhaustive pinching exercise in well-trained athletes, Mana Miyamoto; Kenichi Shibuya; Naoto Sato; Misaki Kaiwa; Kasumi Suzuki; Naomi Kuboyama, 2019, 48, 61, 67, Scientific journal, 10.11183/jhe.48_2.61

Refereed, The effect of food hardness during chewing exercise on autonomic nervous activity, Naoto Sato; Ikumi Asano; Momoka Hatakeyama; Yuki Mitomi; Yuki Kimura; Mana Miyamoto; Kasumi Suzuki; Kenichi Shibuya, 2018, 47, 69, 76, Scientific journal, 10.11183/jhe.47.2_69

Mar. 2024

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Mar. 2022