Meal Timing Regulates the Human Circadian System

The diverse roles of the circadian clock in cancer

A growing part of the human population is affected by circadian misalignment caused by deregulated sleep, increased nighttime light exposure and erratic eating patterns. Thus, circadian rhythms are a key research area, with compelling links to cancer. Here, we review the circadian regulation of critical cellular processes, including immunity, metabolism, cell cycle control and DNA repair, under physiological homeostasis and in cancer. We discuss the divergent evidence indicating tissue-specific roles of the circadian clock in different cancer types and the potential link between circadian misalignment and early-onset cancers. Finally, we outline how understanding the circadian clock can improve cancer prevention and chronomedicine-based therapies.

Time-of-day-dependent effects of a green tea extract on postprandial glycemia and insulinemia in healthy adults: a randomized, controlled, double-blind, cross-over intervention

Glucose homeostasis is intricately associated with circadian rhythms, and disrupting these rhythms, due to mistimed eating, can increase the risk of metabolic dysfunction. Although green tea (poly)phenols are recognized for their potential to lower postprandial glycemia, time-of-day effects of green tea extract incorporated into a starch-based meal remain unexplored. We hypothesized that combining green tea extract with a starch-rich meal could lower postprandial glucose and insulin in both the morning and evening. A four-arm randomized, double-blind, controlled, cross-over intervention was conducted on fourteen healthy adults. Fasted volunteers attended twice in the morning (08:00) and twice in the evening (18:00), consuming either a control (white rice) or test meal (green tea extract-enriched white rice). Blood glucose and insulin concentrations were measured at several time points over 180 minutes, and incremental areas under the curve (iAUC) and peak blood concentrations were calculated. Postprandial glucose levels were higher in the evening compared to the morning, while insulin levels were lower in the evening, regardless of the intervention. The green tea extract meal did not significantly alter the glucose and insulin iAUC compared to the control meal during the morning and evening. Although green tea extract did not affect postprandial glucose concentrations, it significantly decreased peak insulin levels (629 ± 313 pmol L-1, P = 0.04) 30 minutes after the morning meal. Green tea (poly)phenols delay postprandial insulin in the morning but not in the evening, revealing a time-of-day dependent effect on insulin sensitivity.

Exploring Lifestyles and Sensory Processing Patterns of Toddlers in Relation to Sleep Patterns Using Body Movement Analysis

This study explored the impact of lifestyle habits and sensory processing patterns on sleep quality by analyzing body movements (BMs) during the first and last 3 h of sleep in toddlers. We collected cross-sectional data about sleep-related habits from 58 toddlers using a mobile application. Actigraphy measured BMs during nighttime sleep and 1 h before bedtime, as well as sleep latency, over 8 consecutive days. The Infant/Toddler Sensory Profile was used to assess the toddlers' sensory processing patterns. The participants had a mean age of 22.0 ± 2.0 months. BMs were significantly lower during the first 3 h of sleep. Longer sleep latency was significantly associated with media use and higher activity levels before bedtime. Ending a nap earlier and consuming a substantial breakfast were correlated with lower BMs during the first 3 h of sleep. Auditory and oral sensory scores were positively correlated with BMs during the first 3 h of sleep. However, no specific factors related to lifestyle habits or sensory processing patterns were found to correlate with BMs during the last 3 h of sleep. Lifestyle habits and sensory processing patterns have a significant impact on toddlers' sleep quality, emphasizing the importance of appropriate routines and environments.

Advancing Chrononutrition for Cardiometabolic Health: A 2023 National Heart, Lung, and Blood Institute Workshop Report

The circadian system maintains optimal biological functions at the appropriate time of day, and the disruption of this organization can contribute to the pathogenesis of cardiometabolic disorders. The timing of eating is a prominent external time cue that influences the circadian system. "Chrononutrition" is an emerging dimension of nutrition and active area of research that examines how timing-related aspects of eating and nutrition impact circadian rhythms, biological processes, and disease pathogenesis. There is evidence to support chrononutrition as a form of chronotherapy, such that optimizing the timing of eating may serve as an actionable strategy to improve cardiometabolic health. This report summarizes key information from the National Heart, Lung, and Blood Institute's virtual workshop entitled "Chrononutrition: Elucidating the Role of Circadian Biology and Meal Timing in Cardiometabolic Health," which convened on May 2 to 3, 2023, to review current literature and identify critical knowledge gaps and research opportunities. The speakers presented evidence highlighting the impact on cardiometabolic health of earlier and shorter eating windows and more consistent day-to-day eating patterns. The multidimensionality of chrononutrition was a common theme, as it encompasses multiple facets of eating along with the timing of other behaviors including sleep and physical activity. Advancing the emerging field of chrononutrition will require: (1) standardization of terminology and metrics; (2) scalable and precise tools for real-world settings; (3) consideration of individual differences that may act as effect modifiers; and (4) deeper understanding of social, behavioral, and cultural influences. Ultimately, there is great potential for circadian-based dietary interventions to improve cardiometabolic health.

Inverted day-night feeding during pregnancy affects the brain health of both maternal and fetal brains through increasing inflammation levels associated with dysbiosis of the gut microbiome in rats

BACKGROUND

In both humans and rodents, inappropriate feeding times during pregnancy can cause maternal metabolic abnormalities, increasing the risk of neurodevelopmental disorders in both the mother and offspring. Using a rat model, this study investigates whether feeding only during the inactive phase in rats leads to anxiety-like behaviors and abnormal brain development in fetuses through gut microbiota imbalance.

METHODS

10-week-old female rats in the inactive-phase feeding group (IF group) were first trained for daytime feeding, ensuring that energy intake was statistically insignificant and different from that of the normal diet feeding group (ND group). They were then paired with male rats, and the previous feeding regimen was continued after pregnancy. Anxiety-like behavior was evaluated using the open-field test. Maternal caecal microbiota was analyzed using 16S rRNA sequencing. Enzyme-linked immunosorbent assay (ELISA) measured serum inflammation factors. RT-PCR was employed to assess mRNA levels of integrity genes and inflammatory cytokines in the maternal hippocampi, intestines, fetal brains, and placentae.

RESULTS

There were no statistically significant differences in energy intake or body weight gain between the IF and ND groups. In the open field test, dams in the IF group exhibited anxiety-like behavior, as indicated by fewer entries into and shorter duration in the central zone. Active-phase fasting elevated maternal serum inflammatory cytokine levels and impaired antioxidant capacity. It also increased intestinal permeability and induced gut microbiota dysbiosis, characterized by a decrease in Akkermansia and an increase in Dubosiella. Changes in the expression of intestinal circadian genes and elevated intestinal inflammatory cytokines were observed. Lipopolysaccharide (LPS) translocated into the maternal circulation, activated Toll-like receptor 4 (TLR 4), and passed through the compromised placental barrier into the fetal brain, leading to increased expression of inflammatory cytokines in the fetal brain.

CONCLUSIONS

The misalignment between maternal feeding time and the biological clock during pregnancy disrupts the balance of the gut microbiota and peripheral rhythms. The impaired intestinal and placental barriers allow LPS from the gut to infiltrate the maternal hippocampus and fetal brain, increasing inflammation and impacting both maternal and fetal brain health.

Outdoor Exposure to Artificial Light at Night and Breast Cancer Risk: A Case-Control Study Nested in the E3N-Generations Cohort

BACKGROUND

Exposure to light at night (LAN), particularly blue light, is suspected to disrupt circadian rhythm, inhibit melatonin production, and eventually increase the risk of breast cancer.

OBJECTIVES

We assessed the association between exposure to outdoor LAN and breast cancer risk in the E3N-Generations cohort, a large population-based cohort study of French women followed-up from 1990 to 2011.

METHODS

We conducted a nested case-control study in the cohort, including 5,222 incident breast cancer cases and 5,222 matched controls. Outdoor LAN exposure at residential addresses was assessed using radiance-calibrated satellite images from the Defense Meteorological Satellite Program (DMSP). Logistic regression models were used to obtain odds ratios (OR) and 95% confidence intervals (CIs), adjusting for socio-demographic, reproductive, hormonal, and lifestyle-related factors, as well as exposure to air pollutants (NO 2 , PM 2.5 ) evaluated from land use regression and chemistry-transport models, and proximity to greenspaces estimated from the Normalized Difference Vegetation Index (NDVI) in a buffer of 300 m .

RESULTS

Before adjustment for environmental covariates, the ORs associated for LAN exposure increased monotonically from the first to the fourth quartile. This increasing trend was less pronounced after adjustment for air pollutants (NO 2 and PM 2.5 ) and NDVI, but the fully adjusted OR per interquartile range (IQR) of LAN exposure (261  nW / cm 2 / sr ) remained slightly elevated [OR IQR = 1.11 ; 95% confidence interval (CI): 1.02, 1.20]. The adjusted ORs were slightly more elevated in postmenopausal (OR IQR = 1.10 ; 95% CI: 1.02, 1.18) than in premenopausal women and in women living in urban areas with low greenness.

CONCLUSION

The weak positive associations observed in this study that persist after adjustment for environmental covariates, support the hypothesis that outdoor LAN may increase breast cancer risk. Our results, suggesting that urban greenness could mitigate the role of LAN exposure in breast cancer risk, should be investigated further. Future studies on cancer risk in relation to outdoor LAN should assess exposure to indoor sources, including electronic devices, and characterize the light spectrum, particularly the blue light. https://doi.org/10.1289/EHP15105.

Effect of cyclic daytime versus continuous enteral nutrition on circadian rhythms in critical illness (CIRCLES): Study protocol for a randomized controlled trial

BACKGROUND

Circadian rhythms and sleep are often disrupted in critically ill patients in the intensive care unit (ICU), which has been linked to poor clinical outcomes. Feeding-fasting cycles serve as a synchronizing cue for the circadian timing system, indicating that optimizing these cycles in the ICU could reinforce circadian rhythms. The CIRCLES trial evaluates whether cyclic daytime enteral nutrition improves 24-h rhythms in critically ill patients compared to continuous enteral nutrition.

OBJECTIVE

To describe the study protocol for the CIRCLES study.

STUDY DESIGN

The CIRCLES study is an investigator-initiated randomized controlled trial in a tertiary care ICU in the Netherlands. Patients (aged ≥18 years) admitted to the ICU with an expected stay ≥48 h receiving or with intention to start enteral nutrition are eligible for inclusion. Patients (n = 60) are randomized to the continuous enteral nutrition (nutrition around the clock) or cyclic daytime enteral nutrition group (nutrition between 08:00 h to 20:00 h).

MAIN OUTCOME MEASURES

The primary outcome is the amplitude of 24-h rhythms in core body temperature. Secondary outcomes include 24-h rhythms in heart rate, mean blood pressure heart rate variability, melatonin and gene expression, glucose regulation, insulin administration, caloric intake and feeding intolerance.

CONCLUSION

We hypothesize that a cyclic daytime feeding strategy will result in a higher amplitude of 24-h rhythms in vital signs, heart rate variability, and melatonin, compared to continuous feeding, thereby suggesting improved circadian rhythm strength. This study aims to provide insight into strategies to optimize circadian rhythms in ICU patients.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov (NCT05795881), April 2023.

Associations of breakfast habits and breakfast quality with depression symptoms: A cross-sectional study based on NHANES 2007-2018

BACKGROUND

Breakfast, often considered the most important meal of the day, affects both physical and mental health. While most studies focused on the effects of skipping breakfast on depression, few explored the roles of breakfast quality and breakfast time. The study aimed to investigate the association of breakfast habits and breakfast quality with depression symptoms.

METHODS

This study included 23,839 participants aged 20 and older from the 2007-2018 National Health and Nutrition Examination Survey (NHANES). Breakfast habits were assessed using two 24-h dietary recalls, capturing both whether and when breakfast was consumed. Breakfast quality was assessed by calculating the Breakfast Quality Score (BQS). Depression symptoms was diagnosed using the Patient Health Questionnaire (PHQ-9). Binary logistic regression was used to explore the associations.

RESULTS

Compared to participants who did not report breakfast, the ORs of participants who reported breakfast on both one recall and both recalls were 0.737(0.591,0.919) and 0.766(0.624,0.939) for depression symptoms. Compared to participants in the BQS T1 subgroup, the ORs of participants in the T2 subgroup and T3 subgroup were 0.895(0.723,1.108) and 0.716(0.564,0.908) for depression symptoms (P for trend = 0.013). Compared to participants who had breakfast before 8:00 AM, the ORs for depression symptoms were 1.104 (95 % CI: 0.888, 1.371) for those who had breakfast between 8:00-9:00 AM and 1.278 (95 % CI: 1.030, 1.587) for those who had breakfast after 9:00 AM.

CONCLUSIONS

Skipping breakfast, low breakfast quality, and late breakfast are independently associated with depression symptoms.

Circadian clock communication during homeostasis and ageing

Maintaining homeostasis is essential for continued health, and the progressive decay of homeostatic processes is a hallmark of ageing. Daily environmental rhythms threaten homeostasis, and circadian clocks have evolved to execute physiological processes in a manner that anticipates, and thus mitigates, their effects on the organism. Clocks are active in almost all cell types; their rhythmicity and functional output are determined by a combination of tissue-intrinsic and systemic inputs. Numerous inputs for a specific tissue are produced by the activity of circadian clocks of other tissues or cell types, generating a form of crosstalk known as clock communication. In mammals, the central clock in the hypothalamus integrates signals from external light-dark cycles to align peripheral clocks elsewhere in the body. This regulation is complemented by a tissue-specific milieu of external, systemic and niche inputs that modulate and cooperate with the cellular circadian clock machinery of a tissue to tailor its functional output. These mechanisms of clock communication decay during ageing, and growing evidence suggests that this decline might drive ageing-related morbidities. Dietary, behavioural and pharmacological interventions may offer the possibility to overcome these changes and in turn improve healthspan.

Maternal pregnancy diet quality, night eating, and offspring metabolic health: the GUSTO study

BACKGROUND

We investigated the understudied influence of maternal diet quality, food timing, and their interactions during pregnancy on offspring metabolic health.

METHODS

Maternal diet at 26-28 weeks' gestation was assessed using a 24-h recall and adherence to the modified-healthy-eating-index (HEI-SGP) reflects diet quality. Predominant night-eating (PNE) was defined as consuming >50% of total daily energy intake from 19:00 to 06:59. Outcomes were offspring composite metabolic syndrome score and its components measured at age 6 years. Multivariable linear regressions adjusted for relevant maternal and child covariates assessed associations of diet quality and PNE with these outcomes.

RESULTS

Up to 758 mother-child pairs were included. The mean(SD) maternal HEI-SGP score was 52.3(13.7) points (theoretical range: 0-100) and 15% of the mothers demonstrated PNE. Maternal diet quality showed inverse relationship with offspring Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) [β(95% CI): -0.08(-0.15, -0.02) per-10-point HEI-SGP increment; P = 0.012]. Maternal PNE was associated with a higher offspring HOMA-IR [0.28(0.06, 0.50); P = 0.012], with similar estimates after adjustment for children's BMI and diet quality; the association was stronger for boys (P-interaction<0.001) and among mothers with lower diet quality (

CONCLUSIONS

Maternal PNE and low dietary quality were associated with a higher level of insulin resistance in early childhood, especially among boys.

IMPACT

We demonstrated that maternal predominant night-eating behavior and low-quality diet are associated with higher offspring insulin resistance. Maternal low-quality diet and predominant night-eating behavior synergistically interact to influence offspring insulin resistance, particularly among boys. While maternal diet quality and food timing impact the mother's health, their influence on offspring long-term health outcomes through developmental programming is not well understood. Our findings highlight the significance of maternal food timing and calls for further studies on its influence on child health through developmental programming. Targeting both dietary quality and food timing during pregnancy could be a promising intervention strategy.

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MESH Headings

• Female
• Humans
• Pregnancy
• Male
• Diet
• Adult
• Maternal Nutritional Physiological Phenomena
• Insulin Resistance
• Child
• Metabolic Syndrome
• Prenatal Exposure Delayed Effects
• Feeding Behavior

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Affiliation(s)

Ling-Wei Chen Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, No. 17 Xu-Zhou Road, Taipei, 10055, Taiwan. Master of Public Health Program, College of Public Health, National Taiwan University, No. 17 Xu-Zhou Road, Taipei, 10055, Taiwan. A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore.
See Ling Loy Department of Reproductive Medicine, KK Women's and Children's Hospital, Singapore, Singapore Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
Mya Thway Tint A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore Human Potential Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
Navin Michael A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore
Yi Ying Ong Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Road, Singapore, 119228, Singapore Department of Social and Behavioral Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, USA
Jia Ying Toh A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore
Peter D Gluckman Liggins Institute, University of Auckland, 85 Park Rd, Grafton, Auckland, 1023, New Zealand
Kok Hian Tan Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore Department of Maternal Fetal Medicine, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore, 229899, Singapore
Yap-Seng Chong A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore Human Potential Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore Department of Obstetrics & Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Road, Singapore, 119228, Singapore
Keith M Godfrey MRC Lifecourse Epidemiology Centre & NIHR Southampton Biomedical Research Centre, University of Southampton & University Hospital Southampton NHS Foundation Trust, Tremona Road, SO16 6YD, Southampton, UK
Johan G Eriksson A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore Human Potential Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore Department of Obstetrics & Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Road, Singapore, 119228, Singapore Department of General Practice and Primary Health Care, University of Helsinki, Haartmaninkatu 8, 00290, Helsinki, Finland Folkhälsan Research Center, Topeliusgatan 20, 00250, Helsinki, Finland
Fabian Yap Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore Department of Pediatric Endocrinology, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore, 229899, Singapore
Yung Seng Lee A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Road, Singapore, 119228, Singapore Khoo Teck Puat- National University Children's Medical Institute, National University Health System, 1E Kent Ridge Road, Singapore, 119228, Singapore
Mary F F Chong A*STAR Institute for Human Development and Potential (A*STAR IHDP), Agency for Science, Technology and Research (A*STAR), 30 Medical Drive, 117609, Singapore, Singapore Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Singapore

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Neural and hormonal mechanisms of appetite regulation during eating

Numerous animal and clinical studies have demonstrated that the arcuate nucleus of the hypothalamus, a central regulator of appetite, plays a significant role in modulating feeding behavior. However, current research primarily focuses on long-term dietary changes and their effects on the body, with limited investigation into neuroendocrine dynamics during individual meals across diverse populations. In contrast to long-term dietary adjustments, directives for dietary behavior during a specific meal are more actionable, potentially enhancing patient adherence and achieving better outcomes in dietary behavior interventions. This review aimed to explore the neural pathways and endocrine changes activated by gastrointestinal expansion and variations in blood nutrient levels during a single meal, with the goal of informing dietary behavior guidance.

Characterizing 24-Hour Skeletal Muscle Gene Expression Alongside Metabolic and Endocrine Responses Under Diurnal Conditions

CONTEXT

Skeletal muscle plays a central role in the storage, synthesis, and breakdown of nutrients, yet little research has explored temporal responses of this human tissue, especially with concurrent measures of systemic biomarkers of metabolism.

OBJECTIVE

To characterize temporal profiles in skeletal muscle expression of genes involved in carbohydrate metabolism, lipid metabolism, circadian clocks, and autophagy and descriptively relate them to systemic metabolites and hormones during a controlled laboratory protocol.

METHODS

Ten healthy adults (9M/1F, [mean ± SD] age 30 ± 10 years; BMI 24.1 ± 2.7 kg·m-2) rested in the laboratory for 37 hours with all data collected during the final 24 hours (08:00-08:00 hours). Participants ingested hourly isocaloric liquid meal replacements alongside appetite assessments during waking before a sleep opportunity from 22:00 to 07:00 hours. Blood samples were collected hourly for endocrine and metabolite analyses, with muscle biopsies occurring every 4 hours from 12:00 to 08:00 hours the following day to quantify gene expression.

RESULTS

Plasma insulin displayed diurnal rhythmicity peaking at 18:04 hours. Expression of skeletal muscle genes involved in carbohydrate metabolism (Name, Acrophase [hours]: GLUT4, 14:40; PPARGC1A, 16:13; HK2, 18:24) and lipid metabolism (FABP3, 12:37; PDK4, 05:30; CPT1B, 12:58) displayed 24-hour rhythmicity that reflected the temporal rhythm of insulin. Equally, circulating glucose (00:19 hours), nonesterified fatty acids (04:56), glycerol (04:32), triglyceride (23:14), urea (00:46), C-terminal telopeptide (05:07), and cortisol (22:50) concentrations also all displayed diurnal rhythmicity.

CONCLUSION

Diurnal rhythms were present in human skeletal muscle gene expression as well systemic metabolites and hormones under controlled diurnal conditions. The temporal patterns of genes relating to carbohydrate and lipid metabolism alongside circulating insulin are consistent with diurnal rhythms being driven in part by the diurnal influence of cyclic feeding and fasting.

Investigating the association between night eating symptoms and chronotype: the mediating role of depressive symptoms in a sample of Italian university students

PURPOSE

This study aimed to understand the relationship between night eating symptoms, chronotype, and depressive symptoms among Italian university students.

METHODS

The study assessed 905 students using self-report questionnaires, including the night eating questionnaire (NEQ), the Morningness-Eveningness Questionnaire (MEQ), and the Beck depression Inventory (BDI). The correlation between variables was analyzed using Pearson correlation analysis, and mediation analysis was conducted using SPSS PROCESS Macro to estimate the association between variables.

RESULTS

Among the students' sample, the mean age was 25.54 years, with an age range between 18 and 35, 68.7% were women, 15% were morning types with MEQ scores of 59 and above, 64.8% were intermediate types with MEQ scores between 42 and 58, 20.3% were evening types with MEQ scores of 41 and below, and 3.6% reached the criteria for night eating syndrome (NES). There was an inverse correlation between MEQ and BDI scores, higher BDI and lower MEQ scores, and a significant inverse correlation between NEQ and MEQ scores, higher NEQ and lower MEQ scores. Individuals with higher NEQ scores had higher BDI scores, indicating a significant positive correlation between night eating symptoms and depressive symptoms. MEQ had a statistically significant negative direct effect on BDI and NEQ variables. The direct impact of BDI on NEQ was positive and statistically significant. The indirect negative effect of MEQ on NEQ through BDI was also determined to be statistically significant.

CONCLUSION

The study found that depressive symptoms played a significant mediating role in the link between eveningness and night eating, with a partial mediation. Evening chronotype was associated with an elevated night eating score. The findings emphasize the importance of chronotherapeutic approaches in treating night eating. However, further research is necessary to elucidate the intricate relationship between these variables.

LEVEL OF EVIDENCE

Level III. Evidence obtained from well-designed cohort or case-control analytic studies.

Association between Eating-Fasting and Sleep-Wake Cycles with Eating Times and Food Consumption throughout the Day: Longitudinal Study with Pregnant Women

Objective  To investigate the associations of the sleep-eating interval with eating times and food consumption throughout the day in pregnant women. Materials and Methods  A longitudinal study with 100 pregnant women treated at the public health network in the city of Uberlândia, state of Minas Gerais (MG), Brazil, during the entire gestational period. The time intervals between waking up and the first eating episode and between the last eating episode and going to sleep (independent variables) were investigated. Outcome measures were meal and sleep times, as well as food consumption throughout the day. Results  Food consumption closer to sleep at night is associated with higher total daily caloric intake in the first (β = -0.337, p  = 0.016) and second trimesters (Ts) of pregnancy (β = -0.240, p  = 0.023), and with longer sleep duration on weekdays ( p  < 0.05 for all three trimesters). We did not find associations between the wake-up to first eating episode interval and total calories ( p  > 0.05 for all three trimesters), but the longer this interval, the greater the percentage of calories at dinner (1T: β = 0.266, p  = 0.003; 2T: β = 0.269, p  = 0.045) and at the last meal (1T: β = 0.324, p  = 0.001; 2T: β = 0.231, p  = 0.033). Discussion  Taking longer to eat the first meal after waking up is associated with higher caloric intake later in the day, while taking longer to sleep after eating the last meal is associated with higher total daily caloric intake and shorter sleep duration, especially in the beginning and middle of pregnancy.

Intermittent Fasting: Implications for Obesity-Related Colorectal Tumorigenesis

Obesity is associated with metabolic and immune perturbations (ie, insulin resistance, increased inflammation, and oxidative stress), circadian rhythm dysregulation, and gut microbial changes that can promote colorectal tumorigenesis. Colorectal cancer (CRC) is the third most incident cancer in the United States. This narrative review examines the effects of intermittend fasting on factors influencing colon tumorigenesis, such as body weight, metabolic and immune markers, circadian rythm, and the gut microbiota in humans. Findings suggest that intermittent fasting regimens can lead to weight loss and shifts in metabolic markers, which could be preventive for CRC but effects on the gut microbiota composition and functions still remains elusive.

Mistimed Feeding Disrupts Metabolic Rhythm and Increases Lipid Accumulation of Growing Rabbits in Winter

Maintaining the normal biological rhythms of livestock is of great significance for reflecting the environmental suitability and welfare level of animals. Mistimed feeding can interfere with the circadian rhythms of both humans and animals, resulting in disorders of lipid metabolism, obesity, and metabolic syndrome. Low-temperature environment stimulates increased appetite and decreased physical activity, resulting in higher energy intake than consumption and thus facilitating fat deposition and even obesity. In this study, growing rabbits were randomly allocated to the daytime feeding (DF) group and nighttime restricted feeding (NRF) group. Our research demonstrated that, during winter, the DF regimen disrupted the behavioral rhythms of rabbits and accelerated weight gain without changing overall feed intake. The underlying reason was that DF disturbed the lipid metabolism rhythms, promoted hepatic lipid synthesis regulated by DGAT1 and lipid synthesis of adipose tissues regulated by GPAM, thus triggering fat deposition. In contrast, the NRF regimen enhanced thermogenesis regulated by T3 and elevated body temperature and facilitated ketogenesis mediated by HMGCS2, increasing energy consumption. However, it had no significant impact on the fat content within muscle. This study offers a theoretical foundation for the refinement of feeding management and healthy raising of rabbits.

The effect of mediterranean diet and chrononutrition on sleep quality: a scoping review

BACKGROUND

The relationship between diet and sleep quality is intricate, with growing evidence suggesting that dietary patterns and meal timing (chrononutrition) can significantly influence sleep outcomes. This scoping review aims to compare the impact of Mediterranean diet and chrononutrition methods on sleep variables, including sleep quality, duration, and efficiency. While the Mediterranean diet is renowned for its health benefits in chronic diseases, chrononutrition focuses on how the timing of food intake affects health and circadian biology.

METHODS

Literature search following PRISMA guidelines using PubMed and Google Scholar focused on Mediterranean diet and chrononutrition effects on sleep quality. Studies assessed sleep quality using subjective methods like Pittsburgh Sleep Quality Index, analyzing data on study type, sample size, age group, diet, duration, sleep parameters, and outcomes.

RESULTS

Thirty three studies met inclusion criteria, 24 focusing on Mediterranean diet and 9 on chrononutrition. Among the 24 Mediterranean diet studies, most of which were observational studies, 17 reported a positive association between adherence to Mediterranean diet and improved self-reported sleep quality, while the remaining studies found no significant association. In contrast, evidence supporting the positive effects of chrononutrition on sleep quality was limited, with only two out of nine studies having found improvement in sleep quality.

CONCLUSIONS

Mediterranean diet demonstrates a more consistent and positive influence on sleep quality compared to chrononutrition. However, a limitation of review is that the reviewed Mediterranean diet studies were mainly cross-sectional or observational, while the reviewed chrononutrition studies were mainly interventional trials. Larger interventional clinical trials are needed to determine optimal dietary strategies and meal timing for promoting healthy sleep.

Independent effects of the human circadian system and sleep/eating cycles on caloric intake in adolescents vary by weight status

Late-day eating is linked to increased obesity risk; however, whether the endogenous circadian system independently influences caloric intake and if this control differs among individuals based on weight status is unknown. Here, we investigated in adolescents the independent roles of the endogenous circadian system and of the behavioral sleep/wake cycle (sleep/wake, fasting/eating, rest/activity, dark/dim light, social interaction, posture, etc.) on self-selected caloric intake using a Forced Desynchrony protocol. Fifty-one male and female adolescents across three weight status categories (24 with healthy weight, 13 with overweight, and 14 with obesity) completed the protocol where participants lived on seven 28-h sleep/wake cycles in dim light during wake and complete darkness during sleep. Results suggest that the circadian system and the behavioral cycle each affected caloric intake, with a decrease across the wake episode and an increase from circadian morning to circadian evening in caloric intake. The endogenous circadian rhythm in caloric intake showed a circadian peak-to-trough difference of 196 [CI 95% 164, 226] kcal per meal with peak timing of 296° [288°, 304°; equivalent to ~17:30 in these participants]. In those with overweight/obesity, more calories were consumed later in the waking episode and later in the circadian cycle, and with blunted amplitudes compared to those with healthy weight. Results implicate both the endogenous circadian system and the behavioral cycle in shaping the daily rhythm of food intake. Furthermore, these results help explain the increased drive for caloric intake toward the evening, especially in those at risk for obesity.

Stuck in time: The slow march of circadian medicine and how to speed it up

While there is considerable enthusiasm for the translational and clinical applications of chronobiology, their actual implementation is not progressing as rapidly as might be expected. Here we discuss the possibility that this may relate to a combination of conceptual, methodological, evidentiary and training challenges. These are compounded by the remaining, profound cultural differences between basic and applied chronobiologists. We argue that all these issues can be overcome by cross-faculty teaching, time, patience and goodwill, together with a set of more formal actions, such as the establishment of a collaborative framework for evidence generation, the engagement of relevant stakeholders and public health campaigns based on already available evidence. We hope that chronobiology, and in particular the transformative power of circadian medicine, will change health outcomes, increase safety and improve quality of life for patients worldwide. Now is the time to bring "internal time" into medicine.

Circadian Disruption and the Risk of Developing Obesity

PURPOSE OF THE REVIEW

This review summarizes recent evidence for a role of the clock in adipose tissue physiology and the impact of circadian desynchrony on the development of obesity.

RECENT FINDINGS

Circadian disruptions due to shift work, late time eating and nighttime light exposure are associated with obesity and its metabolic and cardiovascular consequences. Studies in mice harboring tissue-specific gain/loss of function mutations in clock genes revealed that the circadian clock acts on multiple pathways to control adipogenesis, lipogenesis/lipolysis and thermogenesis. Time-restricted eating (TRE), aligning feeding with the active period to restore clock function, represents a promising strategy to curb obesity. While TRE has shown clear benefits, especially in participants at higher cardiometabolic risk, current studies are limited in size and duration. Larger, well-controlled studies are warranted to conclusively assess the effects of TRE in relation to the metabolic status and gender. Field studies in shift-workers, comparing permanent night shift versus rotating shifts, are also necessary to identify the optimal time window for TRE.

Circadian rhythm and the influence of light on parameters related to calcium metabolism in stroke patients admitted for rehabilitation

Hospitalized stroke patients are at high risk of developing circadian disruption due to lack of natural sunlight. This may affect the circadian rhythm of the calcium metabolism. This study is a secondary explorative analysis from a Randomized Controlled Trial. Acute stroke patients requiring a minimum of two weeks of rehabilitation were randomized to an Intervention unit (IU) equipped with naturalistic light or a Control unit (CU) with standard indoor lighting. Blood was drawn across 24 h at inclusion and discharge in 45 patients, 25 from the IU and 20 from the CU. Calcium showed significant rhythmicity at inclusion and discharge in both groups. Alkaline phosphatase, parathyroid hormone (PTH), and Vitamin D exhibited no significant rhythmicity at inclusion or discharge in either group while phosphate exhibited rhythmicity at discharge in the CU. PTH levels were elevated in the CU group compared to the IU group at time of discharge. Of the measured parameters, only calcium exhibited circadian rhythmicity after stroke. Naturalistic light did not have any influence on the rhythmicity, indicating that light may not be the main circadian regulator of the circadian oscillations that regulate calcium metabolism. PTH seems to be decreased by naturalistic light.

Association between behavioral jet lag with subjective and objective circadian rhythm among Chinese young adults

BACKGROUND

Behavioral jet lags (social and eating jet lag), the difference in sleep and eating time between weekdays and weekends, are ubiquitous in modern society. However, evidence on the effects of behavioral jet lags on circadian rhythm is limited.

METHODS

Social jet lag was assessed using wrist-worn accelerometers. Eating jet lag was measured through Tencent online form with the method of ecological momentary assessment. Total jet lag was calculated as social jet lag plus eating jet lag. Participants were divided into 3 behavioral jet lag patterns: low (both social and eating jet lag < 1h), medium (social or eating jet lag ≥ 1h), and high (both social and eating jet lag ≥ 1h). Subjective and objective circadian rhythm were assessed by reduced Morningness-Eveningness Questionnaire (rMEQ)-based chronotype and the dim light melatonin onset (DLMO) time in 7 saliva samples, respectively.

RESULTS

The mean age of the sample (n = 140) was 20.7 ± 0.8 years, and 60% were women. Compared to low behavioral jet lag group, medium and high behavioral jet lag group exhibited lower rMEQ score and later DLMO time. Each hour increase in social jet lag was associated with 2.27 point-decrease of rMEQ score, and 24 min-delay of DLMO time; each hour increase in eating jet lag was associated with 1.71 point-decrease of rMEQ score, and 28 min-delay of DLMO time; each hour increase in total jet lag was associated with 1.08 point-decrease of rMEQ score, and 17 min-delay of DLMO time (all P-values <0.05). Additionally, social jet lag explained 6.7% of the variance in the timing of DLMO, which was higher than eating jet lag (4.2%).

CONCLUSION

Higher behavioral jet lags were significantly associated with increased risk of circadian disruption among young adults. Maintaining consistency in daily behavioral cycles may be an effective intervention for the prevention of circadian disruption.

Dietary habits of Koreans aged 95 years and older residing in rural and metropolitan areas

BACKGROUND/OBJECTIVES

Cultural and environmental factors may affect dietary habits and intake, regardless of age. As recent assessments of dietary habits of adults 95 yrs and older are absent, we aimed to determine dietary habits, diet quality, and intake of adults 95 yrs and older and test if they vary by region.

SUBJECTS/METHODS

Adults 95 yrs and older residing in rural areas (Gurye-gun, Goksung-gun, and Sunchang-gun [GuGokSun]; n = 46), a near-city area (Hwasun-gun, and Damyang-gun [HwaDam]; n = 77), and a metropolitan city (Gwangju Metropolitan City [Gwangju]; n = 32) were surveyed. Dietary habits and quality were surveyed using the Nutrition Quotient for the Elderly (NQ-E). Participants (n = 20) recorded videos of their meals, which were subsequently analyzed for food and nutrient intake and compared with intakes of participants of the Korea National Health and Nutrition Examination Survey (KNHANES) aged ≥ 80 yrs (n = 1,769), which were assessed via 24-h recall.

RESULTS

Most participants (85.2%) consumed similar amounts of food at meals; however, only 65.1% ingested meals at regular times. The mean NQ-E score was 48.0 ± 11.9 and did not differ among regions. In Gwangju participants, subjective income was positively associated with diet quality. The mean energy and grain intakes per meal were lower, whereas the percent energy intake from protein and intakes of seaweed, meat and poultry, and iron were higher in GuGokSun and HwaDam participants with meal recordings than in KNHANES participants.

CONCLUSION

Among Korean adults aged ≥ 95 yrs, few regional variations exist in dietary quality and habits, although associations with diet quality vary within regions. Adults 95 yrs and older exhibit lower energy intake but higher intakes of seaweed, meat and poultry, and iron than adults aged ≥ 80 yrs. Notwithstanding, further longitudinal studies on centenarians are warranted.

Challenges and opportunities for statistical power and biomarker identification arising from rhythmic variation in proteomics

Time-of-day variation in the molecular profile of biofluids and tissues is a well-described phenomenon, but-especially for proteomics-is rarely considered in terms of the challenges this presents to reproducible biomarker identification. We provide a case study analysis of human circadian and ultradian rhythmicity in proteins, including in the complement and coagulation cascades and apolipoproteins, with PLG, CFAH, ZA2G and ITIH2 demonstrated as rhythmic for the first time. We also show that rhythmicity increases the risk of Type II errors due to the reduction in statistical power from increased variance, and that controlling for rhythmic time-of-day variation improves statistical power and reduces the chances of Type II errors. We recommend that best practice in proteomics study design should account for temporal variation and that time of sampling be reported as part of study metadata. These simple steps can mitigate against both false and missed discoveries, as well as improving reproducibility.

Chrononutrition in Chronic Kidney Disease

Chrononutrition, the study of the interaction between biological rhythms and nutrition, has emerged as a promising field for addressing metabolic health. However, its role in chronic kidney disease (CKD) remains underexplored. CKD patients often experience circadian disruptions due to renal, metabolic, treatment-related, and lifestyle factors, which may influence their nutritional status and clinical outcomes. Objective: to synthesize and analyze the existing evidence on chrononutrition in CKD patients, identify knowledge gaps, and propose directions for future research across different stages of CKD. Initially, this review contextualizes circadian physiology, alignment, and chronodisruption to explore such factors in CKD patients, focusing on chrononutrition variables already studied in the general population. We discuss how dietary timing and habit adjustments could influence CKD clinical outcomes, offering insights into circadian impacts on disease management. This new approach could optimize patient care, encouraging further research, particularly in the development of personalized strategies for different stages of the disease.

The association between melatonin-containing food consumption and sleep/meal timing and behavior in children with language difficulties

The purpose of this study was to investigate the sleep characteristics, circadian rhythms, behavior, and postnatal development of children with and without language difficulties (LDs) and the association of these variables with melatonin-containing food (FMT) consumption. The study involved parents who anonymously and voluntarily provided their children's personal data and assessed LDs, bedtime, meal timing, behavioral problems, gross motor skill development, and FMT consumption. Multiple regression analysis was used to analyze the associations between study variables. A total of 587 children were examined, with mean age M (SD) 5.5 (2.4) years, (range: 2-12 years), and 44.2% were boys. Children with LD had delayed sleep onset (β = 0.09; R2 = 0.007), increased sleep latency (β = 0.11; R2 = 0.014), social jetlag (β = 0.10; R2 = 0.009), screen time (β = 0.14; R2 = 0.022), and behavioral problems (β = 0.13-0.35; R2 = 0.016-0.142); decreased gestational age at birth (β = -0.09; R2 = 0.007), and delayed development of gross motor skills in the postpartum period (β = 0.11-0.21; R2 = 0.012-0.064). The children's average FMT consumption was 2087.6 ± 2401.3 ng/d. Children with the highest FMT consumption had lower rates of LDs (β = -0.11; R2 = 0.010), social jetlag (β = -0.08; R2 = 0.007), and eating jetlag (β = -0.12; R2 = 0.013); fever behavioral problems (β = -0.09 - -0.10; R2 = 0.007-0.057); and less delayed eating phase (β = -0.11; R2 = 0.012), and development of gross motor skills in the postpartum period (β = -0.10 - -0.12; R2 = 0.009-0.014). In summary, LDs in children were associated with higher rates of circadian misalignment, sleep, behavioral, and developmental dysfunctions, and higher FMT consumption was associated with lower rates of circadian misalignment, behavioral, and developmental dysfunctions. The data obtained indicate the need for a detailed study of the state of the circadian system in preschool and primary school children with language difficulties, which will serve as a rationale for the use of chronotherapy principles for the treatment of this neurological dysfunction.

Fecal microbiota transplantation, a tool to transfer healthy longevity

The complex gut microbiome influences host aging and plays an important role in the manifestation of age-related diseases. Restoring a healthy gut microbiome via Fecal Microbiota Transplantation (FMT) is receiving extensive consideration to therapeutically transfer healthy longevity. Herein, we comprehensively review the benefits of gut microbial rejuvenation - via FMT - to promote healthy aging, with few studies documenting life length properties. This review explores how preconditioning donors via standard - lifestyle and pharmacological - antiaging interventions reshape gut microbiome, with the resulting benefits being also FMT-transferable. Finally, we expose the current clinical uses of FMT in the context of aging therapy and address FMT challenges - regulatory landscape, protocol standardization, and health risks - that require refinement to effectively utilize microbiome interventions in the elderly.

Influence of lifestyle and the circadian clock on reproduction

Background

The biological reproductive process requires the precise coordination of annual and daily signals to adapt to environmental shifts. Humans and animals have developed shared neuroendocrine systems that have adapted to process daily and seasonal light signals within the hypothalamic-pituitary -gonadal axis. However, the stability of circadian and seasonal biological processes is at risk due to industrialization and contemporary round-the-clock lifestyles. These threats include skipping breakfast, excessive artificial illumination during inappropriate hours because of irregular work schedules, nighttime urban lighting, and widespread environmental pollution from endocrine-disrupting chemicals. This review aimed to explore the interplay between lifestyle factors, circadian rhythms, and reproductive functions.

Methods

This review examined the reciprocal influences of circadian clocks on reproductive hormones, exploring the underlying mechanisms and their implications for fertility and reproductive health. We emphasized key findings regarding molecular clock components, endocrine pathways, and the critical importance of synchronizing circadian rhythms with hormonal cycles.

Main Findings

The intersection of reproductive endocrinology and circadian biology reveals complex interactions between hormonal regulation and circadian rhythms. Circadian rhythm misalignments due to environmental factors, including late-night work and skipping breakfast, negatively impact endocrine and reproductive functions.

Conclusions

More strategies are needed to mitigate the effects of circadian disruption on reproductive functions.

Effects of time-restricted feeding and meal timing on an 8-week fat oxidation exercise training program-A randomized controlled trial

Time-restricted feeding (TRF) and aerobic exercise are lifestyle interventions to prevent or manage different metabolic diseases. How these interventions interact, including the impact of meal timing, is not well understood. The aim of this study was to examine the influence of TRF on fat oxidation during exercise, whereby participants performed an 8-week fatmax-training program either in the fasted state or after a carbohydrate-based snack. 36 participants were randomized into three groups. (1) Training sessions were performed in the fasted state; (2) Training sessions were performed after consuming a standardized carbohydrate-based snack; (3) Exercise training with an ad libitum diet as a control group. Pre- and post-tests included anthropometric measurements and a fatmax-cycle-ergometry protocol to measure substrate oxidation. Data were analyzed as workload-matched and maximal fat oxidation using a series of mixed ANOVAs. Workload-matched (p = 0.038) and maximal (p < 0.001) fat oxidation improved in all groups. No significant group × time interactions were found in substrate utilization. Time had a significant effect on body weight (p = 0.011), fat mass (p < 0.001), and muscle mass (p < 0.001). Results suggest that fatmax exercise training leads to improvements in fat oxidative capacity independent of fed or fasted state.

Chronobiological Factors Influencing Glycemic Control and Birth Outcomes in Gestational Diabetes Mellitus

BACKGROUND/OBJECTIVES

Studies have shown that chronobiological factors may adversely affect glycemic control in patients with type 2 diabetes mellitus. We assessed the association of chronobiological factors with glycemic control and neonatal birth weight in women with GDM.

METHODS

A prospective cohort study included 208 women aged 18-45 years with a singleton pregnancy who were randomly selected from among women undergoing follow-up for GDM at the Maternal-Fetal Medicine Unit of a tertiary medical center. Nutrition, sleep, and lifestyle patterns were assessed from onset of GDM until birth along with glycemic control and birth outcomes.

RESULTS

Multivariate analyses on a cohort of 208 women revealed that suboptimal glycemic control was associated with a late breakfast (RR = 2.26; 95% CI 1.09-4.67), increased carbohydrate intake in the evening (RR = 1.19; 95% CI 1.003-1.42), and poor sleep quality (RR = 2.14; 95% CI 1.04-4.41). The adjusted relative risk for neonatal birth weight above the 85th percentile was associated with increased carbohydrate intake in the morning (RR = 1.70; 95% CI 1.30-2.23) and increased carbohydrate intake in the evening (RR = 1.39; 95% CI 1.16-1.67).

CONCLUSIONS

Chronobiological factors are associated with suboptimal glycemic control and birth weight above the 85th percentile in women with GDM. The study was registered under ClinicalTrials.gov.org, identifier: NCT02916667.

Association of the Korean Healthy Eating Index and sleep duration with prediabetes in middle-aged adults

BACKGROUND/OBJECTIVES

Sleep duration and diet quality are reportedly associated with the risk of diabetes. This study aimed to examine the risk of diabetes according to sleep duration and diet quality in middle-aged Koreans.

SUBJECTS/METHODS

Using the Korea National Health and Nutrition Examination Survey 2019-2020, raw data from 2,934 participants aged 40-64 yrs (1,090 men and 1,844 women) who were not diagnosed with type 2 diabetes were analyzed. With a sleep duration of 7-7.9 h per night as the referent category, diet quality was assessed using the Korean Healthy Eating Index (KHEI), which comprises adequacy, moderation, and energy balance.

RESULTS

The study results showed that individuals with a short sleep duration had significantly higher blood glucose (P = 0.034) and HbA1c levels (P < 0.001) than those had by individuals with a sleep duration of 7-7.9 h. Within the group with a sleep duration of 7-7.9 h, the lowest quintile of the KHEI score had a significantly higher risk of prediabetes than that had by the highest quintile of the KHEI score (Model 1: odds ratio [OR], 1.775; 95% confidence interval [CI], 1.072-2.939; P < 0.05 and Model 2: OR, 1.731; 95% CI, 1.040-2.882; P < 0.05).

CONCLUSION

Our findings suggest that achieving the sleep duration of 7-7.9 h and eating good diet are associated with the lowest risk of prediabetes. We recommend that the results of this study be used to educate adults aged 40-64 yrs on diet and lifestyle habits to prevent diabetes.

Maternal dietary and environmental factors associated with infant circadian rhythm, growth, and temperament: Research protocol for a prospective cohort study

Introduction: Emerging evidence has been explored to determine the factors affecting the development of infant circadian rhythm. While fetal programming happens during the pregnancy period, external environmental cues and infant nutritional programming can have substantial effects on the infant circadian rhythm. Understanding prenatal and postnatal factors determining infant circadian rhythm can improve future interventions in optimizing maternal and infant health. Methods: This is a prospective observational cohort study, targeting 216 pregnant women from government maternity clinics in Kuala Lumpur, Malaysia. Pregnant women will be recruited at third trimester (baseline), and follow up at 3 months, and 6 months. A subsample will be collected for salivary cortisol analysis to determine circadian rhythm of the mother and infant at third trimester and 3 months. Data of eating misalignment, light exposure, chronotype, infant temperament, sleep quality, and mood will be collected via validated questionnaires. Anthropometric data and birth outcomes will be collected from antenatal and postnatal health records. Summary: Studies on infant circadian rhythm development have yet to be explored and established, hence this study presents a novel approach to identify the factors from prenatal to postnatal periods on infant circadian rhythm and its influence on growth and temperament. Findings from this study will provide insights in the critical timing which has larger effects on infant circadian rhythm development for future interventions to be conducted.

Selecting, implementing and evaluating control and placebo conditions in light therapy and light-based interventions

Introduction: Light profoundly influences human physiology, behaviour and cognition by affecting various functions through light-sensitive cells in the retina. Light therapy has proven effective in treating seasonal depression and other disorders. However, designing appropriate control conditions for light-based interventions remains a challenge.Materials and methods: This article presents a novel framework for selecting, implementing and evaluating control conditions in light studies, offering theoretical foundations and practical guidance. It reviews the fundamentals of photoreception and discusses control strategies such as dim light, darkness, different wavelengths, spectral composition and metameric conditions. Special cases like dynamic lighting, simulated dawn and dusk, complex interventions and studies involving blind or visually impaired patients are also considered.Results: The practical guide outlines steps for selection, implementation, evaluation and reporting, emphasizing the importance of α-opic calculations and physiological validation.Conclusion: In conclusion, constructing effective control conditions is crucial for demonstrating the efficacy of light interventions in various research scenarios.

Parenteral nutrition results in peripheral ileal to hepatic circadian discordance in mice

We have developed a mouse model of parenteral nutrition-associated liver disease (PNALD) in which parenteral nutrition (PN) infusion results in cholestatic liver injury. In the liver, the master circadian genes Arntl/Bmal drive rhythmic gene expression and regulate circadian expression of hepatic functions including bile acid synthesis. The aim of this study was to examine the effect of continuous PN on ileal and hepatic expression of circadian regulatory (CR) genes, farnesoid X receptor (FXR) signaling, and bile acid synthesis in mice. Wild-type mice were exposed to ad libitum Chow or continuous soy oil lipid emulsion-based PN infusion through a central venous catheter for 4 days (PN). Water was provided ad libitum, but no nutrients were provided enterally. On day 4, separate groups of Chow and PN-fed mice were euthanized every 6 h (7 AM, 1 PM, 7 PM, and 1 AM), and ileal, hepatic tissue and serum harvested. From tissue samples, the relative expression of circadian transcription factors and FXR signaling was assessed. Administration of 4-day PN increased hepatic injury, inflammatory cytokine expression, and gut permeability. In the ileum, PN activated FXR and induced expression of Fgf15 and Nr0b2. In the liver, expression of FXR-downstream targets was dysregulated. PN administrations impacted hepatic and ileal circadian transcription factor mRNA expression, which was discordant between the two organs. Dysregulation of circadian regulatory machinery is in part due to discordance of the gut-liver axis during PN. Pharmacological targeting of CR as a therapeutic strategy for PNALD thus deserves further investigation.NEW & NOTEWORTHY This study used a novel short-term model of parenteral nutrition (PN) that is translationally relevant. We find that short-term PN is sufficient to induce hepatic and ileal changes in circadian transcription factor expression and to prevent normal concordant coordination of circadian transcription factors between the ileum and liver. These data suggest that targeting circadian transcription may have some clinical benefit in patients receiving parenteral nutrition.

The mediating role of obesity in the associations of meal-specific dietary patterns and chrono-nutrition components with cardiometabolic risk factors: structural equation modeling

BACKGROUND

Circadian eating patterns and chrono-nutrition may influence obesity and disease incidence. Thus, this study aimed to assess the mediating role of obesity in the relationship between meal-specific dietary patterns (DPs), chrono-nutritional components, and cardiometabolic risk using structural equation modeling (SEM).

METHODS

A cross-sectional study involving 825 Iranian adults was conducted. Dietary intake was recorded using three 24-h dietary recalls. The morning-evening questionnaire was completed. Meal timing, frequency of eating occasions, and irregular energy scores were derived from dietary recalls. Principal component analysis identified DPs for breakfast, lunch, and dinner. Anthropometric measurements, blood pressure, and laboratory investigations, including fasting glucose levels, lipid profiles, and insulin levels, were performed. Insulin resistance was assessed using the homeostatic model, and triglyceride and glucose indices were calculated.

RESULTS

The final SEM showed, that the "oil, egg, and cereals" DPs at breakfast were directly associated with lipids [β (95% CI); 0.105 (0.007-0.203)]. The "oil, dairy, potato, and egg" DPs at lunch were indirectly linked to increased lipids [0.156 (0.040-0.271), BP (0.338 (0.226-0.449)], and insulin indices [0.208 (0.188-0.277)]. At dinner, the "cereal, oil, poultry, and legume" DPs was directly related to lower BP [- 0.095 (- 0.179 to - 0.012)]. The frequency of eating was directly related to lipid levels (- 0.101 (- 0.193 to - 0.008)]. An irregular energy score was not related to outcomes.

CONCLUSION

More frequent meals and healthier DPs, especially at dinner, were linked to better cardiometabolic outcomes, with obesity mediating some effects. Longitudinal studies are needed to clarify causal relationships.

Weight loss in patients with severe obesity after bariatric surgery-the potential role of the chrono-nutrition, chronotype and the circadian misalignment: A study protocol of the ChronoWise prospective cohort

BACKGROUND

Despite the potential effectiveness of bariatric surgery in promoting weight loss, a considerable proportion of patients still face the challenge of achieving optimal post-surgery outcomes. The timing of eating, in addition to the content of what is eaten, as well as chronotype and social jetlag (a marker of circadian misalignment), have been implicated in weight regulation. However, the current understanding of these chrono-related behaviours in individuals undergoing bariatric surgery is still scarce. Thus, this study aims to evaluate the role of chrono-nutrition, chronotype, and circadian misalignment in the weight-loss trajectory among individuals living with severe obesity who underwent bariatric surgery.

METHODS

The ChronoWise project is a prospective single-centre cohort study designed to follow patients experiencing bariatric surgery at the Santo António Local Health Unit (ULSSA), Porto, Portugal. Participants will be recruited and evaluated at pre-surgery and followed-up over 3 and 6 months after surgery. The baseline evaluation will be conducted face-to-face during the hospital stay and by telephone or video call on the subsequent evaluations, following standard procedures. Data collection includes sociodemographics, food intake, chrono-nutrition behaviours, sleep time behaviour, sleep quality, screen time, physical activity and exercise behaviours, anthropometric measurements, and biochemical parameters. The 'Munich Chronotype Questionnaire' will be used to assess chronotype and social jet lag. Chrono-nutrition dimensions will be measured by the 'Chrononutrition Profile-Questionnaire' in all evaluations. Weight and height will be self-reported and retrieved from medical registries. trajectories of weight-loss will be obtained.

DISCUSSION

This study will add important evidence on the role of chrono-nutrition, chronotype and social jetlag profile in weight-loss outcomes after bariatric surgery. Identifying novel approaches to change the paradigm of post-surgical weight management towards a tailored treatment aligned with circadian rhythm may be useful to strengthen the existing treatments and improve patients' response to bariatric surgery.

Identification of Predictors of Shift Work Adaptation and Its Association With Immune, Hormonal and Metabolite Biomarkers

We explored predictors of shift work adaptation and how it relates to disease risk biomarker levels. These analyses included 38 male, rotating shift workers, sampled twice at the end of a 3-week night shift and a 3-week day shift rotation. Participants collected all 24-h urine voids, wore activity sensors, and responded to questionnaires during each shift. Using cosinor analysis, we derived the main period of urinary 6-sulfatoxymelatonin (aMT6s) production. Adaptation was defined as the overlap between the main aMT6s production period and sleep period assessed with actigraphy. We used linear models to identify predictors of adaptation to each shift and assessed associations between adaptation profiles and hormone, cytokine, and metabolite biomarker levels. The median duration of overlap (adaptation) was 3.85 h (IQR 2.59-5.03) in the night and 2.98 (IQR 2.17-4.11) in the day shift. In the night shift, a later chronotype (coeff: -1.16, 95% CI -1.87, -0.45) and increased light at night (coeff: -0.97, 95% CI -1.76, -0.18) were associated with poorer adaptation, while longer sleep duration was associated with better adaptation (coeff: 0.46, 95% CI 0.04, 0.88). In the day shift, later sleep onset was associated with worse adaptation (coeff: -0.06, 95% CI -0.12, -0.01), while longer sleep duration was associated with better adaptation (coeff: 0.54, 0.26, 0.81). Results suggest higher androgen and inflammatory marker levels and lower levels of several metabolite markers among less adapted individuals. Chronotype, sleep, and light at night were all associated with night or day shift adaptation. Given the small sample size, results should be viewed as exploratory, but may inform interventions to optimize adaptation of rotating shift workers.

Effect of time restricted eating versus current practice in dietetics on glycaemic control and cardio-metabolic outcomes in individuals at risk of developing type 2 diabetes: Protocol for a multi-centre, parallel group, non-inferiority, randomised controlled trial

BACKGROUND

Time restricted eating (TRE) is a dietary strategy that may improve metabolic health. However, no studies have compared TRE with current practice (CP) in dietetics.

HYPOTHESIS

TRE will not be inferior to CP to improve glycaemic control in individuals at risk of type 2 diabetes (T2D).

METHODS

This parallel group, randomised, non-inferiority, controlled trial randomised 247 participants by site and glycated haemoglobin (HbA1c) into TRE or CP (1:1) for 12 months. Participants were aged 35-70 years, with a body mass index (BMI) >25 but <45 kg/m2, and score ≥15 on the Australian type 2 diabetes risk (AUSDRISK) assessment, without a diagnosis of T2D. Study visits were balanced between groups and all participants received five consultations at 0, 0.5, 1, 2 and 3 months. TRE followed a self-selected 9 h eating window (≥0600 and ≤1900), whereas CP followed Australian dietary guidelines.

OUTCOMES

The primary endpoint is the estimate of group mean difference (TRE vs CP) of HbA1c at 4 months in a covariate linear regression adjusting for stratification factors and sex. Secondary efficacy outcomes at 4 and 12 months are changes in fasting glucose, fasting insulin, HOMA-IR and nocturnal glucose by continuous glucose monitor incremental area under the curve and change in HbA1c at 12 months. Other endpoints are exploratory and will not be adjusted for multiplicity.

CONCLUSIONS

We will determine whether TRE is an alternate strategy to current practice in dietetics to improve glucose control.

TRIAL REGISTRATION

NCT04762251; 21 Feb 2021.

Exploring factors influencing late evening eating and barriers and enablers to changing to earlier eating patterns in adults with overweight and obesity

Late evening eating is a potential risk factor for overconsumption and weight gain. However, there is limited qualitative research investigating the complex factors that influence late evening eating in adults living with obesity. Identifying the factors that influence late evening eating can inform interventions to reduce late evening eating and associated health risks. Therefore, this study aimed to: i) explore factors that contribute to eating late, and ii) apply the Capability, Opportunity, and Motivation Behaviour (COM-B) model to understand the barriers and enablers to changing to earlier food intake timings in UK adults who report eating late. Semi-structured interviews with seventeen participants [32.47 ± 6.65 years; 34.68 ± 7.10 kg/m2; 71% female (n = 12); 41% White (n = 7)] investigated reasons for late evening eating and the potential barriers and enablers to changing to earlier eating patterns. Thematic analysis identified four main contributors to late evening eating: 1) internal signals (e.g., feeling hungry in the evening); 2) external and situational factors (e.g., work schedules and the food-rich environment); 3) social factors (e.g., interactions with family) and 4) behavioural and emotional factors (e.g., personal preferences and negative feelings in the evening). Time constraints and work schedules were identified as main barriers to changing to earlier eating patterns. Whereas, having high motivation (e.g., contentment with eating earlier in the evening) and interpersonal support were identified as main enablers to eating earlier. This study provides in-depth insights into the psychological, social, and environmental factors contributing to late evening eating. The findings highlight potential targets for future interventions to facilitate earlier eating times in individuals at risk of overweight and obesity.

Impact of daily breakfast intake on the outcomes of assisted reproductive technology procedures

OBJECTIVE

To assess the relationship between meal consumption frequency and assisted reproductive technology (ART) outcomes among female patients with infertility.

RESEARCH METHODS & PROCEDURES

This cohort study was conducted from February 2022 to January 2024 at Tokyo Medical University Hospital. Overall, 101 female patients with infertility issues and without a history of stroke, heart disease, cancer, or type 1 or type 2 diabetes were enrolled in this study. The factors extracted from the questionnaire included demographic information, meal consumption frequency before ART and at 20 years of age, smoking status, and alcohol consumption status. Data on other factors, including age, body mass index, anti-Müllerian hormone level, and parity history, were collected from medical records. The assessed clinical outcomes included number of transplanted embryos, clinical pregnancies, ongoing pregnancies, live births, and miscarriages.

RESULTS

After adjusting for potential confounding factors, including age, smoking status, alcohol consumption status, body mass index, anti-Müllerian hormone level, and parity history, a multivariate analysis of ART outcomes was performed. Patients were categorized into groups based on the frequency of weekly consumption of breakfast, lunch, and dinner. Patients who consumed breakfast 6-7 times a week were significantly more likely to have higher rates of live birth and lower rates of miscarriage in pregnancies conceived through ART.

CONCLUSIONS

Consumption of breakfast 6-7 times a week before ART was associated with increased success rates following ART. This highlights the potential importance of regular breakfast consumption for optimizing ART outcomes.

Time of Energy Intake: Association with Weight Status, Diet Quality, and Sociodemographic Characteristics in Brazil

This study aimed to estimate the association of time of energy intake with weight status, diet quality, and sociodemographic characteristics in Brazil. This cross-sectional study used data from a nationally representative survey with 44.744 individuals (≥10 years old). Food consumption was assessed by 24 h recall. The evening/morning energy intake ratio was calculated, standardized, and categorized in tertiles. The association between the evening/morning energy intake ratio and weight status was estimated using polynomial logistic regression models, and differences across diet quality and sociodemographic categories were estimated considering the non-overlapping 95% confidence intervals. Men, adolescents, adults, and individuals in the higher income level had greater evening energy intake. Those with a higher evening-to-morning energy intake ratio were 15% more likely to be obese (OR = 1.15; 95% CI = 1.02 to 1.28), 21% less likely to be underweight (OR = 0.79; 95% CI = 0.64 to 0.98), and reported greater total energy, protein, and lipid intake, as well as higher consumption of low-quality diet markers. Higher evening energy intake relative to morning intake was associated with obesity, low-quality diet markers, and sociodemographic characteristics. The characterization of the time of energy intake can be useful for tailoring and targeting diet promotion actions and for controlling the obesity epidemic.

Meal Timing and Depression Among Chinese Children and Adolescents: Cross-Sectional Study

Background

Depression in children and adolescents is a rising concern in China. Dietary behavior is a critical determinant of mental health. Meal timing, or the schedule of meal consumption, has been related to several metabolic disorders. However, the effect of meal timing on mental health is scarce, particularly in children and adolescents who are in a critical period of physical and psychological development.

Objective

This research examined the relationship between meal timing and depression in children and adolescents in China.

Methods

Children and adolescents from grades 1 to 9 were recruited from 16 districts in Shanghai, China, from January 3 to January 21, 2020. Ten schools attended the study. A survey was distributed to the students and their parents to collect demographic and health-related information. Depression was measured by the Children's Depression Inventory-Short Form. Breakfast consumption was analyzed as a binary outcome. Participants were defined as breakfast consumers if they never skipped breakfast during the week. They were otherwise defined as breakfast skippers if they skipped breakfast at least once per week. A similar categorization was applied to analyze food intake proximal to bed. Daily eating windows were calculated using the last food intake time frame-the first food intake time frame. Participants were classified into eating window groups of less than 10 hours, 10-12 hours, and more than 12 hours. A logistic regression model was used to compute the odds ratio (OR) and 95% CI.

Results

A total of 6874 participants were included in the analysis. Participants who skipped breakfast were associated with a 2.70 times higher occurrence of depression (OR 2.70, 95% CI 2.24-3.26; P<.001). The prevalence of depression was 1.28 times higher in participants who ate before bed than in those who never ate before bed (OR 1.28, 95% CI 1.08-1.50; P<.001). The occurrence of depression was 1.37 times higher if the eating time window was shorter than 10 hours (OR 1.37, 95% CI 1.08-1.73; P=.009) and 1.23 times higher if the eating time window was longer than 12 hours (OR 1.23, 95% CI 1.01-1.50; P=.004). The lowest occurrence of depression was observed at 11.5 hours. Subgroup analysis showed that such relationships remained significant in adolescents aged 10 years or older. In children, only skipping breakfast was associated with a higher odds of depression (OR 2.77, 95% CI 1.94-3.96; P<.001).

Conclusions

Breakfast skipping and eating before bed significantly increase the occurrence of depression. The optimal daily eating window to lower the occurrence of depression is 11.5 hours in children and adolescents. Daily eating windows longer than 12 hours or shorter than 10 hours are associated with an elevated occurrence of depression. Current findings advocate evidence-based dietary strategies to prevent and treat depression in children and adolescents.

Chrononutrition and metabolic health in children and adolescents: a systematic review and meta-analysis

CONTEXT

Obesity has emerged as a global health issue for the pediatric population, increasing the need to investigate physiopathological aspects to prevent the appearance of its cardiometabolic complications. Chrononutrition is a field of research in nutritional sciences that investigates the health impact of 3 different dimensions of feeding behavior: regularity of meals, frequency, and timing of food intake.

OBJECTIVE

We carried out a systematic review and meta-analysis to investigate the association between chrononutrition in children and adolescents and the risk of overweight/obesity or a cluster of metabolic abnormalities related to glucose and lipid metabolism, blood pressure, and cardiovascular disease risk.

DATA EXTRACTION

A literature search was performed using PubMed, EMBASE, and The Cochrane Library for relevant articles published before August 2022.

DATA ANALYSIS

A total of 64 articles were included in the narrative synthesis (47 cross-sectional and 17 cohort studies), while 16 studies were included in the meta-analysis. Meta-analysis showed that non-daily breakfast consumers (≤6 d/wk) had a higher risk of overweight/obesity (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.08-1.82] compared with daily breakfast eaters (7 d/wk). Similarly, irregular breakfast consumption (only 0-to-3 times/wk) increased the risk of abdominal obesity (waist-to-height ratio ≥ 0.5) compared with regular consumption (5-to-7 times/wk) (OR, 1.38; 95% CI, 1.26-1.49). There was evidence to suggest that a regular frequency of meal consumption (≥4 times/d) is preventive against overweight/obesity development compared with fewer meals (≤3 times/d) (OR, 0.83; 95% CI, 0.70-0.97). In the narrative synthesis, snacking habits showed controversial results, while food timing was the most understudied dimension.

CONCLUSION

Overall, our data indicate a potential implication of chrononutrition in affecting pediatric metabolic health; however, the evidence of this association is limited and heterogeneous. Further prospective and intervention studies with a consistent approach to categorize the exposure are needed to elucidate the importance of chrononutrition for pediatric metabolic health.

Adaptation of sleep to daylight saving time is slower in people consuming a high-fat diet

Adaptation of the circadian clock to the environment is essential for optimal health, well-being, and performance. Animal models demonstrate that a high-fat diet impairs circadian adaptation to advances of the light-dark cycle; it is unknown whether this occurs in humans. Utilizing a natural experiment that occurs when humans must advance their behaviors to an earlier hour for daylight saving time (DST), we measured the influence of diet on sleep/wake timing relative to dim-light melatonin onset time. Students with a lower-fat diet rapidly altered their sleep-wake timing to match the imposed time change, whereas those with a high-fat diet were slower to adapt to the time change. Moreover, a faster shift in timing after DST was associated with higher general health, lower body mass index, and higher grade point average. These data suggest that diet may influence the speed of sleep and circadian adaptation, which could have implications for health and performance.

Time-restricted eating affects human adipose tissue fat mobilization

OBJECTIVE

Time-restricted eating (TRE), a dietary approach that confines food intake to specific time windows, has shown metabolic benefits. However, its impact on body weight loss remains inconclusive. The objective of this study was to investigate the influence of early TRE (eTRE) and delayed TRE (dTRE) on fat mobilization using human adipose tissue (AT) cultures.

METHODS

Subcutaneous AT was collected from 21 participants with severe obesity. We assessed fat mobilization by measuring glycerol release in AT culture across four treatment conditions: control, eTRE, dTRE, and 24-h fasting.

RESULTS

TRE had a significant impact on lipolysis (glycerol release [mean (SD)] in micromoles per hour per gram: control, 0.05 [0.003]; eTRE, 0.10 [0.006]; dTRE, 0.08 [0.005]; and fasting, 0.17 [0.008]; p < 0.0001). Both eTRE and dTRE increased lipolysis compared with the control group, with eTRE showing higher glycerol mobilization than dTRE during the overall 24-h time window, especially at the nighttime/habitual sleep episode (p < 0.0001). Further analysis of TRE based on fasting duration revealed that, independently of the time window, glycerol release increased with fasting duration (in micromoles per hour per gram: 8 h = 0.08 [0.001]; 12 h = 0.09 [0.008]; and 16 h of fasting = 0.12 [0.011]; p < 0.0001).

CONCLUSIONS

This study provides insights into the potential benefits of TRE on fat mobilization and may guide the design of future dietary strategies for weight management and metabolic health.

Associations between temporal eating patterns and body composition in young adults: a cross-sectional study

PURPOSE

The aim of this study was to examine the associations between body composition and temporal eating patterns, including time of first eating occasion, time of last eating occasion, eating window, and eating jet lag (the variability in meal timing between weekdays and weekends).

METHODS

A total of 131 participants were included in the study. Temporal eating pattern information was collected through consecutive 7-day eat timing questionnaires and photographic food records. Body composition was assessed by bioelectrical impedance analysis. Multiple linear regression models were used to evaluate the relationships of temporal eating patterns with body composition, and age was adjusted. Eating midpoint was additionally adjusted in the analysis of eating window.

RESULTS

On weekdays, both later first eating occasion and last eating occasion were associated with lower lean mass, and longer eating window was associated with lower body fat percentage. On weekends, both later first eating occasion and last eating occasion were associated with lower lean mass, and longer eating window was associated with higher FFMI. Longer first eating occasion jet lag was associated with lower lean mass.

CONCLUSION

Our study suggested that earlier and more regular eating patterns may have a benefit on body composition.

From Garden to Pillow: Understanding the Relationship between Plant-Based Nutrition and Quality of Sleep

The effect of diet on sleep quality has been addressed in many studies; however, whether/how plant-based diets (PBDs) impact sleep-related parameters has not been explored in detail. This review aims to give an overview of the components of PBDs and the possible mechanisms through which PBDs may improve sleep quality. Studies have indicated that diets such as PBDs, which are typically high in fruits, vegetables, nuts, seeds, whole grains, and fiber, are associated with better sleep outcomes, including less fragmented sleep and improved sleep duration. Several mechanisms may explain how PBDs impact and/or improve sleep outcomes. Firstly, PBDs are characteristically rich in certain nutrients, such as magnesium and vitamin B6, which have been associated with improved sleep patterns. Secondly, PBDs are often lower in saturated fats and higher in fiber, which may contribute to better overall health, including sleep quality. Additionally, plant bioactive compounds like phytochemicals and antioxidants in fruits, vegetables, and herbs may have sleep-promoting effects. According to available data, PBD and Mediterranean diet elements promise to enhance sleep quality; however, it is crucial to note that diets should be customized based on each person's needs.

Exploring the associations between chronotype, meal frequency, and physical activity: A population-based study in adults

Chronotype is an established concept designed to capture the internal clock's phase in real-life conditions. It is vital in many aspects of daily life and can interfere considerably with numerous factors in a given population. Recognizing nonmodifiable and modifiable factors is crucial for identifying covariates of interest when studying the link between chronotype and health status. To date, chronotype and its related factors have not been extensively investigated. The present study aimed to explore the association of chronotypes with meal frequency, physical activity, and demographic factors among the Saudi population. This cross-sectional web-based questionnaire involved 1369 adults (aged 18 years and above) from the general public in Saudi Arabia and was conducted between March and May 2019. Chronotype was assessed using the reduced version of the original Horne and Ostberg morningness-eveningness questionnaire (MEQ). Meal frequencies and demographics data (age, gender, marital status, place of residence, educational level, employment status, income) were obtained. Physical activity level was also obtained using the international physical activity questionnaire. The MEQ scores group individuals into three categories: morning-type, neither-type, and evening-type. The neither-type individuals represented 41.6% (95% confidence interval [CI], 37.5% - 45.6%) of the study population, followed by the morning-type (34.1%; 95% [CI], 29.8% - 38.4%), then the evening-type (24.3%, 95% [CI], 19.6% - 28.9%). Chronotype was significantly associated with age, marital status, employment status and monthly income (All p < 0.05). Significant associations between chronotype with meal frequencies (number of meals per day, breakfast frequency, lunch frequency, and dinner frequency) and physical activity were also observed (All p < 0.05). This study highlights that meal frequencies and physical activity levels are associated with chronotype distribution. Furthermore, demographics, including age, marital status, employment status, and income, were associated with chronotype distribution.

Chrono-nutrition and sleep: lessons from the temporal feature of eating patterns in human studies - A systematic scoping review

An emerging field of research has revealed a bidirectional relationship between sleep and diet, highlighting the potential role of a healthy diet in improving sleep. However, the impact of chrono-nutrition on sleep remains less explored. Here we conducted a systematic scoping review, considering the multiple dimensions of chrono-nutrition, to describe the extent, range, and nature of the existing literature in this area (PROSPERO: CRD42021274637). There has been a significant increase in the literature exploring this topic over the past six years (almost 67 % of the evolving literature). A breakdown of the included studies was performed according to three major chrono-nutritional dimensions: meal timing [n = 35], irregular eating patterns [n = 84], and frequency of eating occasions [n = 3]. Meal timing included three sub-dimensions: breakfast skipping [n = 13], late eating [n = 16], and earlier vs later meals schedules [n = 6]. Irregular meal patterns included three sub-dimensions: diurnal fasting [n = 65], intermittent fasting [n = 16], and daily meal patterns [n = 3]. Frequency was the least studied dimension (n = 3). We provided a synthetic and illustrative framework underlining important preliminary evidence linking the temporal characteristics of eating patterns to various facets of sleep health. Nonetheless, much work remains to be done to provide chrono-nutrition guidelines to improve sleep health in the general population.