Examining the evidence between screen time and night eating behaviour with dietary intake related to metabolic syndrome: A narrative review

Screen time (ST) on digital devices has increased in recent decades due to digital development. Furthermore, constant engagement with digital devices alters sleep patterns, leading to nocturnal eating behaviour among users. These phenomena are therefore of great concern, as digital device addiction and night eating are associated with unhealthy food intake, increasing the metabolic syndrome (MetS) risks. The purpose of this review was to examine the evidence of the influence of ST and night eating behaviour (NEB) on dietary intake and its association with MetS based on previous literature. Prolonged ST and NEB have an association with excessive intake of energy from overconsumption of high-sugar and high-fat foods. However, the relationship between digital content and its influence on food intake is inconsistent. A higher MetS risk was found in individuals with longer ST due to a sedentary lifestyle, while positive energy balance and a shift in circadian rhythm contributed to night eaters. ST and NEB presented with a significant influence on food intake in adults. Additionally, unhealthy food intake due to excessive consumption of empty-calorie foods such as sweet and fatty foods due to addiction to electronic devices and eating at night has a detrimental effect on metabolic function. Therefore, improving food intake by reducing ST and night binges is essential to reduce the risk of MetS.

Effects of (Poly)phenols on Circadian Clock Gene-Mediated Metabolic Homeostasis in Cultured Mammalian Cells: A Scoping Review

Circadian clocks regulate metabolic homeostasis. Disruption to our circadian clocks, by lifestyle behaviors such as timing of eating and sleeping, has been linked to increased rates of metabolic disorders. There is now considerable evidence that selected dietary (poly)phenols, including flavonoids, phenolic acids and tannins, may modulate metabolic and circadian processes. This review evaluates the effects of (poly)phenols on circadian clock genes and linked metabolic homeostasis in vitro, and potential mechanisms of action, by critically evaluating the literature on mammalian cells. A systematic search was conducted to ensure full coverage of the literature and identified 43 relevant studies addressing the effects of (poly)phenols on cellular circadian processes. Nobiletin and tangeretin, found in citrus, (-)-epigallocatechin-3-gallate from green tea, urolithin A, a gut microbial metabolite from ellagitannins in fruit, curcumin, bavachalcone, cinnamic acid, and resveratrol at low micromolar concentrations all affect circadian molecular processes in multiple types of synchronized cells. Nobiletin emerges as a putative retinoic acid-related orphan receptor (RORα/γ) agonist, leading to induction of the circadian regulator brain and muscle ARNT-like 1 (BMAL1), and increased period circadian regulator 2 (PER2) amplitude and period. These effects are clear despite substantial variations in the protocols employed, and this review suggests a methodological framework to help future study design in this emerging area of research.

Construct validity and test-retest reliability of a chrononutrition questionnaire for shift work and non-shift work populations

The irregular eating patterns of both shift workers and evening chronotypes adversely affect cardiometabolic health. A tool that conveniently captures temporal patterns of eating alongside an indicator of circadian rhythm such as chronotype will enable researchers to explore relationships with diverse health outcome measures. We aimed to investigate the test-retest reliability and convergent validity of a Chrononutrition Questionnaire (CNQ) that captures temporal patterns of eating and chronotype in the general population (non-shift workers, university students, retirees, unemployed individuals) and shift work population. Participants attended two face-to-face/virtual sessions and completed the CNQ and food/sleep/work diaries. Outcomes included subjective chronotype, wake/sleep/mid-sleep time, sleep duration, meal/snack regularity, meal/snack/total frequency, times of first/last/largest eating occasions (EO), main meal (MM) 1/2/3, and duration of eating window (DEW). 116 participants enrolled (44.5 ± 16.5 years, BMI: 27.3 ± 5.8 kg/m2, 73% female, 52% general population); 105 completed the study. Reliability was acceptable for chronotype, sleep, and all temporal eating patterns except on night shifts. Convergent validity was good for chronotype and sleep except for certain shift/shift-free days. Generally, meal/snack regularity and frequency, and times of first/last EO showed good validity for the general population but not shift workers. Validity was good for DEW (except work-free days and afternoon shifts) and times of MM 1/2/3 (except afternoon and night shifts), while time of largest EO had poor validity. The CNQ has good test-retest reliability and acceptable convergent validity for the general and shift work population, although it will benefit from further validation, especially regarding regularity, frequency, and times of first and last eating occasions across more days amongst a larger sample size of shift workers. Use of the CNQ by researchers will expand our current understanding of chrononutrition as relationships between timing of food intake and the multitude of health outcomes are examined.

Night eating in timing, frequency, and food quality and risks of all-cause, cancer, and diabetes mortality: findings from national health and nutrition examination survey

OBJECTIVE

To investigate the association of timing, frequency, and food quality of night eating with all-cause, cancer, and diabetes mortality.

METHODS

This study included 41,744 participants from the US National Health and Nutrition Examination Survey (2002-2018). Night eating information was collected by 24-h dietary recall and the exposures were timing, frequency, and food quality of night eating. Food quality was assessed by latent class analysis. The outcomes were all-cause, cancer, and diabetes mortality, which were identified by the National Death Index and the International Classification of Diseases 10th Revision. Adjusted hazard ratios [aHR] with 95% confidence intervals [CI] were computed by Cox regression.

RESULTS

During a median follow-up of 8.7 years, 6066 deaths were documented, including 1381 from cancer and 206 from diabetes. Compared with no night eating (eating before 22:00), the later timing of night eating was associated with higher risk of all-cause and diabetes mortality (each P-trend <0.05) rather than cancer mortality, with the highest risk of eating being 00:00-1:00 (aHR 1.38, 95% CI 1.02-1.88) and being 23:00-00:00 (aHR 2.31, 95% CI 1.21-4.40), respectively. However, the increased risks were not observed for 22:00-23:00. Likewise, one time or over frequency of night eating was associated with higher all-cause and diabetes mortality (each P < 0.05). That risks were further observed in high-dietary-energy-density group of night eating (all-cause mortality: aHR 1.21 [95% CI 1.06-1.38]; diabetes mortality: aHR 1.97 [95% CI 1.13-3.45]), but not in low-dietary-energy-density group. Finally, correlation analysis found positive associations of night eating with glycohemoglobin, fasting glucose, and OGTT.

CONCLUSIONS

Night eating was associated with increased all-cause, cancer and diabetes mortality; however, reduction of excess mortality risk was observed when eating before 23:00 or low-dietary-energy-density foods.

Various types of fasting diet and possible benefits in nonalcoholic fatty liver: Mechanism of actions and literature update

Non-alcoholic fatty liver disease (NAFLD) is one of the major causes of chronic liver injury, affecting around one-fourth of the general population across the world. Several important pathophysiological mechanisms underlying NAFLD include oxidative stress, inflammation, liver fibrosis, and apoptosis. Currently, therapeutic approaches are not ideal for managing NAFLD, thus new approaches and treatments are still needed. Over the last two decades, various fasting protocols have been explored to reduce body weight and improve metabolic disorders. In this review, we provide updated literature that supports fasting regimens for subjects with NAFLD and describes underlying mechanisms of action. We suggest that fasting regimens may modulate NAFLD via several mechanisms, including changes in gut microbiota, hepatic arginase, hepatic autophagy, inflammatory responses, liver functional enzymes and hepatic steatosis, fibroblast growth factors signaling, white adipose tissue browning, adipokines, circadian rhythms, lipid profiles, and body composition.

Chrononutrition-When We Eat Is of the Essence in Tackling Obesity

Obesity is a chronic and relapsing public health problem with an extensive list of associated comorbidities. The worldwide prevalence of obesity has nearly tripled over the last five decades and continues to pose a serious threat to wider society and the wellbeing of future generations. The pathogenesis of obesity is complex but diet plays a key role in the onset and progression of the disease. The human diet has changed drastically across the globe, with an estimate that approximately 72% of the calories consumed today come from foods that were not part of our ancestral diets and are not compatible with our metabolism. Additionally, multiple nutrient-independent factors, e.g., cost, accessibility, behaviours, culture, education, work commitments, knowledge and societal set-up, influence our food choices and eating patterns. Much research has been focused on 'what to eat' or 'how much to eat' to reduce the obesity burden, but increasingly evidence indicates that 'when to eat' is fundamental to human metabolism. Aligning feeding patterns to the 24-h circadian clock that regulates a wide range of physiological and behavioural processes has multiple health-promoting effects with anti-obesity being a major part. This article explores the current understanding of the interactions between the body clocks, bioactive dietary components and the less appreciated role of meal timings in energy homeostasis and obesity.

The Impact of Job-Demand-Control-Support on Leptin and Ghrelin as Biomarkers of Stress in Emergency Healthcare Workers

Despite the available literature on the consequences of night shiftwork on stress and food intake, its impact on leptin and ghrelin has never been studied. We previously demonstrated that leptin and ghrelin were biomarkers related to stress, and acute stress-induced a decrease in leptin levels and an increase in ghrelin levels. We performed a prospective observational study to assess the influence of night work, nutrition, and stress on the levels of ghrelin and leptin among emergency healthcare workers (HCWs). We took salivary samples at the beginning of a day shift and/or at the end of a night shift. We also monitored stress using the job demand-control-support model of Karasek. We recorded 24-h food intake during the day shift and the consecutive night shift and during night work and the day before. We included 161 emergency HCWs. Emergency HCWs had a tendency for decreased levels of leptin following the night shift compared to before the dayshift (p = 0.067). Furthermore, the main factors explaining the decrease in leptin levels were an increase in job-demand (coefficient -54.1, 95 CI -99.0 to -0.92) and a decrease in job control (-24.9, -49.5 to -0.29). Despite no significant changes in ghrelin levels between shifts, social support was the main factor explaining the increase in ghrelin (6.12, 0.74 to 11.5). Food intake (kcal) also had a negative impact on leptin levels, in addition to age. Ghrelin levels also decreased with body mass index, while age had the opposite effect. In conclusion, we confirmed that ghrelin and leptin as biomarkers of stress were directly linked to the job demand-control-support model of Karasek, when the main cofounders were considered.

Dietary Risk Factors and Eating Behaviors in Peripheral Arterial Disease (PAD)

Dietary risk factors play a fundamental role in the prevention and progression of atherosclerosis and PAD (Peripheral Arterial Disease). The impact of nutrition, however, defined as the process of taking in food and using it for growth, metabolism and repair, remains undefined with regard to PAD. This article describes the interplay between nutrition and the development/progression of PAD. We reviewed 688 articles, including key articles, narrative and systematic reviews, meta-analyses and clinical studies. We analyzed the interaction between nutrition and PAD predictors, and subsequently created four descriptive tables to summarize the relationship between PAD, dietary risk factors and outcomes. We comprehensively reviewed the role of well-studied diets (Mediterranean, vegetarian/vegan, low-carbohydrate ketogenic and intermittent fasting diet) and prevalent eating behaviors (emotional and binge eating, night eating and sleeping disorders, anorexia, bulimia, skipping meals, home cooking and fast/ultra-processed food consumption) on the traditional risk factors of PAD. Moreover, we analyzed the interplay between PAD and nutritional status, nutrients, dietary patterns and eating habits. Dietary patterns and eating disorders affect the development and progression of PAD, as well as its disabling complications including major adverse cardiovascular events (MACE) and major adverse limb events (MALE). Nutrition and dietary risk factor modification are important targets to reduce the risk of PAD as well as the subsequent development of MACE and MALE.

Shift workers’ perceptions and experiences of adhering to a nutrition intervention at night whilst working: a qualitative study

This study explored the feasibility of implementing a meal timing intervention during night shift work. Data were collected via semi-structured interviews. Interviews were coded inductively by two researchers independently, then three major themes were collaboratively developed. Subthemes from each major theme were mapped to the theoretical domains framework and the Capability Opportunity Motivation model of behaviour change. Seventeen night shift workers (rotating or permanent) aged between 25 and 65 years were interviewed. Participants predominately worked as health professionals. The feasibility of a simple meal timing intervention to avoid eating between 1 and 6 am on night shift is largely affected by three major influences (1) physical and emotional burden of shift work which drives food temptations; (2) the workplace context including the meal break environment, social and cultural context at work, and break scheduling; and (3) motivation of the individual. Facilitators to avoiding eating at night were, keeping busy, having co-worker support, management support, education of health benefits and/or belief that the intervention was health promoting. The barriers to avoiding eating at night were the emotional and physical toll of working at night leading to comfort eating and not having rest areas away from food environments. To support night shift workers with changing timing of meals, interventions at work should target both individual and organisational level behaviour change.

The association between long-term night shift work and metabolic syndrome: a cross-sectional study of male railway workers in southwest China

OBJECTIVES

Metabolic syndrome (MetS) increases the risk of new diabetes and cardiovascular disease. Night shift work (NSW) may influence metabolic disturbance and lead to MetS. This study aims to investigate the association between long-term NSW (≥ 10 years) and MetS combined with its components in male railway workers in southwest China.

METHODS

11,023 male railway workers with long-term NSW of more than 10 years in the Physical Examination Center of the Affiliated Hospital of Chengdu University were enrolled. The basic data were collected by investigators and blood test results were collected. The primary outcome was the prevalence of metabolic syndrome. The results were analyzed using statistical software SPSS 22.0.

RESULTS

In total, 11,023 people over the age of 40 with more than 10 years of working experience were enrolled, and 4759 (43.2%) participants had a diagnosis of MetS. The basic data indicated that night shift workers tended to be younger, shorter working years, but with higher body mass index and longer hip circumference (p < 0.05). The adjusted analysis revealed that there was no significant association between NSW and metabolic syndrome (OR 1.03, 95% CI 0.94-1.12, p = 0.543). NSW was associated with SBP ≥ 130 mmHg (OR 1.11, 95% CI 1.02-1.21, p < 0.001) and waist circumference ≥ 90 cm (OR 1.11, 95% CI 1.02-1.21, p < 0.001).

CONCLUSIONS

Long-term night shift workers had a higher prevalence of MetS. However, long-term NSW is not associated with a significantly increased risk of metabolic syndrome in male railway workers in southwest China. Long-term NSW is associated with elevated SBP, and waist circumference increase.

The Impact of Meal Timing on Risk of Weight Gain and Development of Obesity: a Review of the Current Evidence and Opportunities for Dietary Intervention

PURPOSE OF REVIEW

The aim of this short review is to provide an updated commentary on the current literature examining the impact of meal timing on obesity and weight gain in adults. The potential mechanisms, including novel and emerging factors, behind timing of food intake across the 24-h period in the development of obesity, and dietary strategies manipulating meal timing to ameliorate weight gain are also explored.

RECENT FINDINGS

Dietary patterns that feature meal timing outside of the regular daytime hours can contribute to circadian disruption as food is metabolised in opposition to internal daily rhythms and can feedback on the timekeeping mechanisms setting these rhythms. Epidemiological evidence examining the impact of late meal timing patterns is beginning to suggest that eating at night increases the risk of weight gain over time. Mechanisms contributing to this include changes to the efficiency of metabolism across the day, and dysregulation of appetite hormone and gut microbiota by mis-timed meals. When meals are eaten, in relation to the time of day, is increasingly considered of importance when implementing dietary change in order to address the growing burden of obesity, although further research is required in order to determine optimal patterns.

Performance Nutrition for Physician Trainees Working Overnight Shifts: A Randomized Controlled Trial

PURPOSE

To compare acute effects of 2 dietary interventions with usual dietary habits on physician trainees' alertness during overnight shifts.

METHOD

This registered, controlled, block randomized crossover trial (NCT03698123) was conducted between October 2018 and May 2019 at Stanford Medicine. Physician trainees working at least 3 overnight shifts during a 1-week period were recruited. During the first night, participants followed their usual dietary habits. During the intervention nights (low carbohydrate-to-protein ratio and high carbohydrate-to-protein ratio interventions), participants received healthy dinners, snacks, water, and, upon request, caffeinated beverages, at the beginning of their shifts and were instructed to eat meals before 10 pm. The sequence of interventions on the second and third nights were block randomized across study weeks. Outcome measures (a priori) were overnight changes in validated measures of specific neurobehavioral dimensions: psychomotor vigilance, sensory-motor speed, working memory, and risk decision making, as well as self-reported sleepiness and work exhaustion.

RESULTS

Sixty-one physician trainees participated in this study. Compared with usual dietary habits, overnight changes in psychomotor vigilance scores (scale 0-1,000) improved by 51.02 points (95% CI: 12.08, 89.96) and sleepiness (scale 1-7) improved by 0.69 points (95% CI: 0.33, 1.05) under the low carbohydrate-to-protein ratio intervention. Compared with usual dietary habits, overnight changes in sleepiness (scale 1-7) improved by 0.61 points (95% CI: 0.25, 0.96) under the high carbohydrate-to-protein ratio intervention. Neither intervention had beneficial effects relative to usual dietary habits with respect to sensory-motor speed, working memory, risk decision making, or work exhaustion. There were no differences in outcomes between low carbohydrate-to-protein ratio and high carbohydrate-to-protein ratio interventions.

CONCLUSIONS

Dietary interventions may mitigate negative effects of physician trainee sleep deprivation during overnight shifts. Future studies are warranted to further examine the effectiveness of nutritional strategies on physician alertness during overnight shifts.

The Negative Impact of Night Shifts on Diet in Emergency Healthcare Workers

Despite the consequences of night-shift work, the diet of night-shift workers has not been widely studied. To date, there are no studies related to food intake among emergency healthcare workers (HCWs). We performed a prospective observational study to assess the influence of night work on the diet of emergency HCWs. We monitored 24-h food intake during a day shift and the consecutive night, and during night work and the daytime beforehand. We analyzed 184 emergency HCWs' food intakes. Emergency HCWs had 14.7% lower (-206 kcal) of their 24-h energy intake during night shifts compared to their day-shift colleagues (1606.7 ± 748.2 vs. 1400.4 ± 708.3 kcal, p = 0.049) and a 16.7% decrease in water consumption (1451.4 ± 496.8 vs. 1208.3 ± 513.9 mL/day, p = 0.010). Compared to day shifts, night-shift had 8.7% lower carbohydrates, 17.6% proteins, and 18.7% lipids. During the night shift the proportion of emergency HCWs who did not drink for 4 h, 8 h and 12 h increased by 20.5%, 17.5%, and 9.1%, respectively. For those who did not eat for 4 h, 8 h and 12 h increased by 46.8%, 27.7%, and 17.7%, respectively. A night shift has a huge negative impact on both the amount and quality of nutrients consumed by emergency healthcare workers.

Face Validity of Observed Meal Patterns Reported with 7-Day Diet Diaries in a Large Population-Based Cohort Using Diurnal Variation in Concentration Biomarkers of Dietary Intake

In a cross-sectional analysis of a population-based cohort (United Kingdom, N = 21,318, 1993-1998), we studied how associations between meal patterns and non-fasting triglyceride and glucose concentrations were influenced by the hour of day at which the blood sample was collected to ascertain face validity of reported meal patterns, as well as the influence of reporting bias (assessed using formula of energy expenditure) on this association. Meal size (i.e., reported energy content), mealtime and meal frequency were reported using pre-structured 7-day diet diaries. In ANCOVA, sex-specific means of biomarker concentrations were calculated by hour of blood sample collection for quartiles of reported energy intake at breakfast, lunch and dinner (meal size). Significant interactions were observed between breakfast size, sampling time and triglyceride concentrations and between lunch size, sampling time and triglyceride, as well as glucose concentrations. Those skipping breakfast had the lowest triglyceride concentrations in the morning and those skipping lunch had the lowest triglyceride and glucose concentrations in the afternoon, especially among acceptable energy reporters. Eating and drinking occasion frequency was weakly associated with glucose concentrations in women and positively associated with triglyceride concentrations in both sexes; stronger associations were observed for larger vs. smaller meals and among acceptable energy reporters. Associations between meal patterns and concentration biomarkers can be observed when accounting for diurnal variation and underreporting. These findings support the use of 7-day diet diaries for studying associations between meal patterns and health.

Content Validation of a Chrononutrition Questionnaire for the General and Shift Work Populations: A Delphi Study

Unusual meal timing has been associated with a higher prevalence of chronic disease. Those at greater risk include shift workers and evening chronotypes. This study aimed to validate the content of a Chrononutrition Questionnaire for shift and non-shift workers to identify temporal patterns of eating in relation to chronotype. Content validity was determined using a Delphi study of three rounds. Experts rated the relevance of, and provided feedback on, 46 items across seven outcomes: meal regularity, times of first eating occasion, last eating occasion, largest meal, main meals/snacks, wake, and sleep, which were edited in response. Items with greater than 70% consensus of relevance were accepted. Rounds one, two, and three had 28, 26, and 24 experts, respectively. Across three rounds, no outcomes were irrelevant, but seven were merged into three for ease of usage, and two sections were added for experts to rate and comment on. In the final round, all but one of 29 items achieved greater than 70% consensus of relevance with no further changes. The Chrononutrition Questionnaire was deemed relevant to experts in circadian biology and chrononutrition, and could represent a convenient tool to assess temporal patterns of eating in relation to chronotype in future studies.

Relationship between Dietary Habits and Control of Lipid Profiles in Patients with Dyslipidemia Using Pravastatin

We investigated the association between dietary habits, evaluated using the modified Mini Dietary Assessment Index for Koreans (MDA), and lipid control among patients aged ≥20 years who had used pravastatin for dyslipidemia for 6 months. Participants were administered questionnaires regarding sociodemographic characteristics and lifestyle factors. Odds ratios and 95% confidence intervals for the control of low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and total cholesterol (TC) at 6 months for each category of the modified MDA items were calculated through multivariate logistic regression analysis. The odds for controlled LDL-C was higher among those who consumed cholesterol-rich foods <1 time/week (3.27, 1.25–8.57) than for those who did so ≥4 times/week. The odds for controlled TG was higher among those who always consumed dairy products (2.96, 1.36–6.44), ate protein-rich foods three times/day (2.94, 1.06–8.10), and had a regular eating schedule (3.02, 1.30–7.00) than among those who did not have any of these. The odds for controlled TC was higher among those with a regular eating schedule (3.47, 1.55–7.76) than among their counterparts. Patients with dyslipidemia should consume less cholesterols, consume more dairy and protein-rich foods, and follow a regular eating schedule to control lipid profiles.

The Window Matters: A Systematic Review of Time Restricted Eating Strategies in Relation to Cortisol and Melatonin Secretion

Time-Restricted Eating is an eating pattern based on the circadian rhythm which limits daily food intake (usually to ≤12 h/day), unique in that no overt restriction is imposed on the quality, nor quantity, of food intake. This paper aimed to examine the effects of two patterns of TRE, traditional TRE, and Ramadan fasting, on two markers of circadian rhythm, cortisol and melatonin. PubMed and Web of Science were searched up to December 2020 for studies examining the effects of time restricted eating on cortisol and melatonin. Fourteen studies met our inclusion criteria. All Ramadan papers found statistically significant decrease in melatonin (p < 0.05) during Ramadan. Two out of the three Ramadan papers noted an abolishing of the circadian rhythm of cortisol (p < 0.05). The non-Ramadan TRE papers did not examine melatonin, and cortisol changes were mixed. In studies comparing TRE to control diets, Stratton et al. found increased cortisol levels in the non-TRE fasting group (p = 0.0018) and McAllister et al. noted no difference. Dinner-skipping resulted in significantly reduced evening cortisol and non-significantly raised morning cortisol. Conversely, breakfast skipping resulted in significantly reduced morning cortisol. This blunting indicates a dysfunctional HPA axis, and may be associated with poor cardio-metabolic outcomes. There is a paucity of research examining the effects of TRE on cortisol and melatonin. The contrasting effect of dinner and breakfast-skipping should be further examined to ascertain whether timing the feeding window indeed has an impact on circadian rhythmicity.

A scoping review of chronotype and temporal patterns of eating of adults: tools used, findings, and future directions

Circadian rhythms, metabolic processes and dietary intake are inextricably linked. Timing of food intake is a modifiable temporal cue for the circadian system and may be influenced by numerous factors, including individual chronotype - an indicator of an individual's circadian rhythm in relation to the light-dark cycle. This scoping review examines temporal patterns of eating across chronotypes and assesses tools that have been used to collect data on temporal patterns of eating and chronotype. A systematic search identified thirty-six studies in which aspects of temporal patterns of eating, including meal timings; meal skipping; energy distribution across the day; meal frequency; time interval between meals, or meals and wake/sleep times; midpoint of food/energy intake; meal regularity; and duration of eating window, were presented in relation to chronotype. Findings indicate that, compared with morning chronotypes, evening chronotypes tend to skip meals more frequently, have later mealtimes, and distribute greater energy intake towards later times of the day. More studies should explore the difference in meal regularity and duration of eating window amongst chronotypes. Currently, tools used in collecting data on chronotype and temporal patterns of eating are varied, limiting the direct comparison of findings between studies. Development of a standardised assessment tool will allow future studies to confidently compare findings to inform the development and assessment of guidelines that provide recommendations on temporal patterns of eating for optimal health.

Time-of-day and Meal Size Effects on Clinical Lipid Markers

CONTEXT

Dyslipidemia and cardiovascular disease are common in shift workers and eating at night may contribute to this pathophysiology.

OBJECTIVE

To examine the effects of eating at different times of day on lipid profiles.

DESIGN

Two 24-hour baseline days with 8 hours of sleep, 3 meals (breakfast, lunch, dinner) and a snack, followed by a 40-hour constant routine (CR) with hourly isocaloric meals.

SETTING

Intensive Physiological Monitoring Unit, Brigham and Women's Hospital.

PARTICIPANTS

Twenty-one healthy adults [23.4 ± 2.7 years, 5F].

INTERVENTION

Forty-hour CR.

MAIN OUTCOME MEASURES

A standard clinical lipid panel, consisting of total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), was assayed in blood samples collected 4-hourly across ~4 days.

RESULTS

When participants ate at night, levels of TG were similar to eating during the day, however, these levels at night were reached with consuming approximately half the calories. Additionally, 24-hour levels of TG were 10% higher when meals were consumed hourly across 24 hours compared to consuming a typical 3-meal schedule while awake during the day and sleeping at night. The endogenous circadian rhythms of TG, which peaked at night, were shifted earlier by ~10 hours under baseline conditions, whereas the rhythms in total cholesterol, HDL-C, and LDL-C remained unchanged and peaked in the afternoon.

CONCLUSIONS

The time-of-day dependency on postprandial lipid metabolism, which leads to hypersensitivity in TG responses when eating at night, may underlie the dyslipidemia and elevated cardiovascular disease risk observed in shift workers.

Eating breakfast and avoiding late-evening snacking sustains lipid oxidation

Circadian (daily) regulation of metabolic pathways implies that food may be metabolized differentially over the daily cycle. To test that hypothesis, we monitored the metabolism of older subjects in a whole-room respiratory chamber over two separate 56-h sessions in a random crossover design. In one session, one of the 3 daily meals was presented as breakfast, whereas in the other session, a nutritionally equivalent meal was presented as a late-evening snack. The duration of the overnight fast was the same for both sessions. Whereas the two sessions did not differ in overall energy expenditure, the respiratory exchange ratio (RER) was different during sleep between the two sessions. Unexpectedly, this difference in RER due to daily meal timing was not due to daily differences in physical activity, sleep disruption, or core body temperature (CBT). Rather, we found that the daily timing of nutrient availability coupled with daily/circadian control of metabolism drives a switch in substrate preference such that the late-evening Snack Session resulted in significantly lower lipid oxidation (LO) compared to the Breakfast Session. Therefore, the timing of meals during the day/night cycle affects how ingested food is oxidized or stored in humans, with important implications for optimal eating habits.

Late-Night Eating-Induced Physiological Dysregulation and Circadian Misalignment Are Accompanied by Microbial Dysbiosis

SCOPE

Irregular eating habits, such as late-night eating, will cause increased risk of obesity and other metabolic diseases. The aim of this study is to elucidate the impacts of late-night eating on physiological function and gut microbiota.

METHODS AND RESULTS

Male Wistar rats under 16 h/8 h-light/dark cycle are divided into four groups with specific dietary habits, which mimicked breakfast, lunch, dinner, and late-night eating. Late-night eating, including skipping dinner for a night eating (BLN) and skipping breakfast and having a night eating (LDN), causes an increase of body weight, which is associated with decreased physical activity. Additionally, late-night eating results in hepatic lipid accumulation and systemic inflammation in peripheral tissues, compared to those of free feeding (FF) or breakfast, lunch, and dinner (BLD) groups. The phases of key clock genes are similar in FF, BLD, and BLN groups, while LDN feeding causes an overall 4 h phase delay in peripheral tissues. Moreover, late-night eating, especially LDN feeding, results in a significant alternation in the compositions and functions of gut microbiota, which further contributes to the development of metabolic disorder.

CONCLUSION

Late-night eating causes physiological dysregulation and misalignment of circadian rhythm, together with microbial dysbiosis.