We aimed to investigate the association of chrono-nutrition components with anthropometric measures and body composition in adults living in Tehran. This cross-sectional study was conducted on 450 healthy adults. The exposures of the study were meal frequency, meal timing, meal irregularity, breakfast skipping, night fasting duration, time of the first and last eating occasion (EO), and the time interval from the last meal to bed. The outcomes were body mass index (BMI), waist circumference (WC), neck circumference (NC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), body adiposity index (BAI), body roundness index (BRI), A body shape index (ABSI), percentage of body fat (PBF), fat mass (FM), fat-free mass (FFM), and muscle mass (MM). Bonferroni correction was applied and the significance level was less than 0.004. Using ANCOVA, after adjusting for confounders, late lunch eating was associated with a lower PBF. There was a positive trend across the tertiles of dinner time with greater WHtR (mean difference=0.019; Ptrend=0.025) and BRI (mean difference=0.24; Ptrend=0.022). Moreover, increased irregularity at dinner time was associated with higher levels of PBF (Ptrend=0.026) and FM (Ptrend=0.025). Also, longer overnight fasting was associated with lower NC (Ptrend=0.049) and a greater BRI (Ptrend=0.050). We found differences across the time interval from the last meal to bed with greater means of BAI (Ptrend=0.026), PBF (Ptrend=0.014), and FM (Ptrend=0.020). However, after applying the Bonferroni correction, we found no significant association between chrono-nutrition components and anthropometric measures and body composition in adults living in Tehran. Further studies are necessary to confirm the results.

Melatonin is an easily accessible, widely used drug for sleep issues, disrupted sleep–wake cycles, and jet lag, available in a variety of forms and dosages. Melatonin is also used in hospital settings to promote sleep onset, particularly in elderly patients, as a circadian rhythm regulator. Despite the popularity of melatonin, it is not approved by the US Food and Drug Administration (FDA). This creates ambiguity surrounding its proper usage for optimum results, including dosage and time of administration. The objective of this article is to shed light on the best timing to administer melatonin. Melatonin is a hormone that our body naturally produces to regulate our biological clock. Even though our body has a built-in “sleep system,” many people still suffer from chronic sleep disorders such as insomnia. Melatonin has also proved to help prevent delirium in hospitalized patients due to its circadian rhythm regulatory effects. The elderly are at risk of developing insomnia because as one ages, melatonin production decreases. The most convenient solution for insomnia is to take melatonin supplements. To optimize the effects of melatonin supplements, proper dosage and timing must be considered. Additionally, patients who are oppositional to bedtime, which is known as bedtime resistance, are typically more willing to go to bed following melatonin administration. Melatonin administration at around 6 PM (1–2 hours before bedtime) is optimal to regulate sleep cycles of patients, and it can help with bedtime resistance. This should be the standard of care in all hospitals, nursing homes, and at home.

Circadian rhythms are intrinsic, endogenously generated cycles that regulate various physiological processes, including reproductive functions. These rhythms are orchestrated by a network of core clock genes and are influenced by external environmental cues, primarily the light–dark cycle. Disruptions in circadian rhythms can have profound effects on fertility in both males and females, impacting processes such as the estrous cycle, ovulation, sperm production, implantation and pregnancy maintenance. This review comprehensively explores the molecular mechanisms underlying circadian rhythms and their influence on reproductive health, integrating evidence from both animal models and human studies. We delve into the intricate interplay between circadian genes, hormonal regulation and environmental factors, underscoring the critical importance of circadian integrity for optimal reproductive outcomes. The potential therapeutic implications of maintaining circadian rhythms are also discussed, highlighting novel avenues for enhancing reproductive health.

Traders in global markets operate at different local times-of-day. This implies heterogeneity in circadian timing and likely sleepiness or alertness of those traders operating at less or more optimal times of the day, respectively. This, in turn, may lead to differences in both individual-level trader behavior as well as market level outcomes. We examined these factors by administering single-location and global sessions of an online asset market experiment that regularly produces mispricing and valuation bubbles. Global sessions involved real time trades between subjects in New Zealand and the U.S (i.e., “global” markets) with varied local times of day for each location. Individual traders at suboptimal times of day (or, “circadian mismatched” traders) engaged in riskier trading strategies, such as holding shares (the riskier asset) in later trading rounds and mispricing shares to a greater degree. These strategies resulted in lower earnings for circadian mismatched traders, especially in heterogeneous markets that also included traders at more optimal times-of-day. These differences were also reflected in market level outcomes. Markets with higher circadian mismatch heterogeneity across traders were more likely to exhibit longer lasting asset bubbles and greater share turnover volume. Overall, our results draw attention to a unique, but underappreciated, factor present across traders in global market environments, namely, differences in sleepiness across traders. Thus, this study hopes to highlight the role of circadian mismatch in attempting to understand trader behavior and, ultimately, market volatility.

As obesity rates rise globally, addressing modifiable lifestyle factors, such as sleep, presents an opportunity for public health interventions. This review explores the growing evidence linking sleep duration, quality and timing with weight management and dietary behaviours throughout the life course. Observational studies associate short or irregular sleep with increased obesity risk, poor diet quality and metabolic disturbances. Plausible mechanisms include decreased physical activity, heightened hedonic and/or emotional eating, dysregulated appetite signals and circadian misalignment of metabolism, which contribute to a positive energy balance. Unravelling the bidirectional relationship between sleep and weight is challenging; poor sleep exacerbates weight gain, while obesity-related comorbidities such as obstructive sleep apnoea further impair sleep. Despite promising evidence from sleep-restriction studies showing increased energy intake, long-term randomised controlled trials (RCTs) examining interventions designed to improve sleep with weight management as an outcome are lacking. A handful of short-term interventions suggest benefits in reducing energy intake or improving dietary quality, but their effects on weight loss remain inconclusive. This review calls for robust, well-powered RCTs that integrate sleep, diet and physical activity interventions to evaluate the potential of sleep as a core component of obesity prevention and treatment strategies. Currently, there is insufficient evidence to support sleep-focused interventions as a mandatory element in clinical weight-management programmes.

Timing of food intake is an emerging aspect of nutrition; however, there is a lack of research accurately assessing food timing in the context of the circadian system. The study aimed to investigate the relation between food timing relative to clock time and endogenous circadian timing with adiposity and further explore sex differences in these associations among 151 young adults aged 18–25 years. Participants wore wrist actigraphy and documented sleep and food schedules in real time for 7 consecutive days. Circadian timing was determined by dim-light melatonin onset (DLMO). The duration between last eating occasion and DLMO (last EO-DLMO) was used to calculate the circadian timing of food intake. Adiposity was assessed using bioelectrical impedance analysis. Of the 151 participants, 133 were included in the statistical analysis finally. The results demonstrated that associations of adiposity with food timing relative to circadian timing rather than clock time among young adults living in real-world settings. Sex-stratified analyses revealed that associations between last EO-DLMO and adiposity were significant in females but not males. For females, each hour increase in last EO-DLMO was associated with higher BMI by 0·51 kg/m2 (P = 0·01), higher percent body fat by 1·05 % (P = 0·007), higher fat mass by 0·99 kg (P = 0·01) and higher visceral fat area by 4·75 cm2 (P = 0·02), whereas non-significant associations were present among males. The findings highlight the importance of considering the timing of food intake relative to endogenous circadian timing instead of only as clock time.

Obesity is a chronic, complex and multi-factorial condition with an increasing prevalence worldwide. Irregular eating schedules might be a contributing factor to these numbers through the dysregulation of the circadian system. Time-restricted eating (TRE), an approach that limits eating windows, has been studied as a strategy to treat obesity, aligning eating occasions with metabolic circadian rhythms. This review aims to provide an overview of the impact of TRE protocols on metabolic, inflammatory, oxidative stress and circadian rhythm biomarkers in people with overweight or obesity. Most studies report significant weight loss following TRE protocols. While glucose levels decreased in nearly all TRE interventions, only a few studies demonstrated statistically significant differences when compared to the control groups. The findings for c-reactive protein and TNF-α were inconsistent, with limited significant differences. Changes in lipid profile changes were variable and generally did not reach statistical significance. Both 4-hour and 6-hour TRE interventions significantly reduced 8-isoprostane levels. Additionally, TRE significantly altered clock gene expression, as well as that of genes associated with metabolic regulation in subcutaneous adipose tissue. While the evidence is still inconsistent, limiting eating to a consistent daily window of 8 to 12 h can improve insulin sensitivity, reduce blood glucose, cholesterol and triglyceride levels and promote weight loss. These effects are likely attributable to both direct metabolic impacts and indirect benefits from weight loss and improved dietary habits. However, data on circadian, inflammatory and specific metabolic biomarkers remain scarce and occasionally contradictory, highlighting the need for further research on these interventions.

Chrono-medicine considers circadian biology in disease management, including combined lifestyle and medicine interventions. Exercise and nutritional interventions are well-known for their efficacy in managing type 2 diabetes, and metformin remains a widely used pharmacological agent. However, metformin may reduce exercise capacity and interfere with skeletal muscle adaptations, creating barriers to exercise adherence. Research into optimising the timing of exercise has shown promise, particularly for glycaemic management in people with type 2 diabetes. Aligning exercise timing with circadian rhythms and nutritional intake may maximise benefits. Nutritional timing also plays a crucial role in glycaemic control. Recent research suggests that not only what we eat but when we eat significantly impacts glycaemic control, with strategies like time-restricted feeding (TRF) showing promise in reducing caloric intake, improving glycaemic regulation and enhancing overall metabolic health. These findings suggest that meal timing could be an important adjunct to traditional dietary and exercise approaches in managing diabetes and related metabolic disorders. When taking a holistic view of Diabetes management and the diurnal environment, one must also consider the circadian biology of medicines. Metformin has a circadian profile in plasma, and our recent study suggests that morning exercise combined with pre-breakfast metformin intake reduces glycaemia more effectively than post-breakfast intake. In this review, we aim to explore the integration of circadian biology into type 2 diabetes management by examining the timing of exercise, nutrition and medication. In conclusion, chrono-medicine offers a promising, cost-effective strategy for managing type 2 diabetes. Integrating precision timing of exercise, nutrition and medication into treatment plans requires considering the entire diurnal environment, including lifestyle and occupational factors, to develop comprehensive, evidence-based healthcare strategies.

In the question put forward by Scott et al., implications about the role of immune activation in depressive or other mood disorders were suggested. Low-level inflammation, triggered by the release of inflammatory molecules such as cytokines, has been detected in individuals with major mood disorders. These markers can be present in very low concentrations, posing a significant analytical challenge and complicating their use as reliable biomarkers. In this Perspective, we discuss the potential promise in leveraging nanotechnology and trace-level analysis of biomarkers of immune activation to enhance our molecular understanding of the immune system’s functioning and its association with depressive and other mood disorders. This Perspective critically discusses the analytical challenges of trace biomarker detection, highlighting issues with variability in study methodologies and cohort heterogeneity and emphasising the need for diurnal and longitudinal sampling to study circadian disruption and immune activation. Profiling inflammatory markers in this manner could create individualised molecular fingerprints, revealing disruptions in immune synchronisation with circadian rhythms and detecting abnormalities linked to specific mood disorder subtypes, and particularly ‘circadian depression’. As the profiling of general inflammatory markers may not be sufficient to study any causative relationship between immune activation and major mood disorders, we propose the exploration of novel biomarkers such as extracellular vesicles to support these investigations. The use of nanotechnologies for trace profiling of diurnal variations of inflammatory molecules, in combination with novel biomarkers, offers a promising strategy to develop a molecular understanding of the role of immune activation in depressive and other mood disorders.

Menaquinone-7 (MK-7), a multipotent vitamin K2, possesses a wide range of biological activities, a precise curative effect and excellent safety. A simple and rapid LC-APCI-MS/MS method for the determination of MK-7 in human plasma with single liquid–liquid extraction (LLE) extraction and 4·5-min analysis time has been developed and validated. Four per cent bovine serum albumin (BSA) was used as surrogate matrix for standard curves and endogenous baseline subtraction. This method was reproducible and reliable and was used to analyse of MK-7 in human plasma. The endogenous circadian rhythm and bioavailability of MK-7 were investigated in two randomised single-dose, open, one-way clinical trials (Study I and Study II). A total of five healthy male subjects were enrolled in Study I and 12 healthy male subjects in Study II. Single-dose (1 mg) of MK-7 was given to each subject under fasting condition, and all eligible subjects were given a restricting VK2 diet for 4 d prior to drug administration and during the trial. The experiment results of Study I demonstrated that endogenous MK-7 has no circadian rhythm in individuals. Both studies showed MK-7 are absorbed with peak plasma concentrations at about 6 h after intake and has a very long half-life time.

A device for analysing mouse behaviour which is based on recording the movements of the animal in a balance test cage has been developed. The amplitude patterns provoked by the movements of the animal correlate with behavioural patterns. The system not only allows differentiation between five behavioural categories: resting, grooming, eating, locomotion and climbing - but also indicates the location of the animal in its cage. Upon validation, the system has proven to be a reliable and time-saving device for the non-invasive recording of behavioural patterns in the mouse.

Considerable research has pointed towards processing differences as a viable means for understanding the strength and likelihood of a framing effect. In the current study we explored how differences in processing may emerge through diurnal patters in circadian rhythm, which varies across individuals. We predicted that during circadian off-times, participants would exhibit stronger framing effects whereas framing effects would be relatively weaker during on-times. Six-hundred and eighty five individuals took part in the study; the findings supported our hypothesis, revealing a diurnal pattern of risk responding that varies across the 24-hour circadian cycle.

Bipolar disorder (BD) is a potentially chronic mental disorder marked by recurrent depressive and manic episodes, circadian rhythm disruption, and changes in energetic metabolism. “Metabolic jet lag” refers to a state of shift in circadian patterns of energy homeostasis, affecting neuroendocrine, immune, and adipose tissue function, expressed through behavioral changes such as irregularities in sleep and appetite. Risk factors include genetic variation, mitochondrial dysfunction, lifestyle factors, poor gut microbiome health and abnormalities in hunger, satiety, and hedonistic function. Evidence suggests metabolic jet lag is a core component of BD pathophysiology, as individuals with BD frequently exhibit irregular eating rhythms and circadian desynchronization of their energetic metabolism, which is associated with unfavorable clinical outcomes. Although current diagnostic criteria lack any assessment of eating rhythms, technological advancements including mobile phone applications and ecological momentary assessment allow for the reliable tracking of biological rhythms. Overall, methodological refinement of metabolic jet lag assessment will increase knowledge in this field and stimulate the development of interventions targeting metabolic rhythms, such as time-restricted eating.