The association among circadian rhythm, circadian genes and chrononutrition, its effect on obesity: a review of current evidence

Circadian rhythms, also known as circadian clocks, are cyclic endogenous biological patterns of an approximately 24-hour cycle which regulate the timing of physiology, metabolism, and behavior. Recent research in the field of circadian science has suggested that the timing of food intake may also play a role in markers of health, in addition to food choice and food quantity. There is emerging evidence suggesting that the timing of dietary intake, so-called chrono-nutrition, may be influenced by an individual<apos;>s chronotype. For example, the evening type has been linked to unhealthy diet, which could indicate a higher possibility of obesity. On the other hand, the continuum of chronotype diversity is largely mediated by genes. The presence of single nucleotide polymorphisms (SNP) of clock genes have been associated with obesity, chronotype, metabolic disturbances, and dietary habits (e.g., breakfast skipping, meal timing, energy/macronutrient intake). In this review, we outline the current knowledge of the interactions between clock genes, chronotype, dietary intake and chrono-nutrition.Additionally, it is emphasized that the COVID-19 pandemichas had a significant impact on the circadian system, dietary choices and meal timing. For this reason, the current review aims to focus on how chronotype/sleep and chrono-nutrition are affected during the COVID-19 pandemic.Copyright © 2022 Informa UK Limited, trading as Taylor & Francis Group.

Meal-timing patterns and chronic disease prevalence in two representative Austrian studies.

PURPOSE: This study aimed at describing meal-timing patterns using cluster analysis and explore their association with sleep and chronic diseases, before and during COVID-19 mitigation measures in Austria. METHODS: Information was collected in two surveys in 2017 (N = 1004) and 2020 (N = 1010) in representative samples of the Austrian population. Timing of main meals, nighttime fasting interval, last-meal-to-bed time, breakfast skipping and eating midpoint were calculated using self-reported information. Cluster analysis was applied to identify meal-timing clusters. Multivariable-adjusted logistic regression models were used to study the association of meal-timing clusters with prevalence of chronic insomnia, depression, diabetes, hypertension, obesity and self-rated bad health status. RESULTS: In both surveys, median breakfast, lunch and dinner times on weekdays were 7:30, 12:30 and 18:30. One out of four participants skipped breakfast and the median number of eating occasions was 3 in both samples. We observed correlation between the different meal-timing variables. Cluster analysis resulted in the definition of two clusters in each sample (A17 and B17 in 2017, and A20 and B20 in 2020). Clusters A comprised most respondents, with fasting duration of 12-13 h and median eating midpoint between 13:00 and 13:30. Clusters B comprised participants reporting longer fasting intervals and later mealtimes, and a high proportion of breakfast skippers. Chronic insomnia, depression, obesity and self-rated bad health-status were more prevalent in clusters B. CONCLUSIONS: Austrians reported long fasting intervals and low eating frequency. Meal-timing habits were similar before and during the COVID-19-pandemic. Besides individual characteristics of meal-timing, behavioural patterns need to be evaluated in chrono-nutrition epidemiological studies.

Late chronotypes, late mealtimes. Chrononutrition and sleep habits during the COVID-19 lockdown in Italy.

The emerging field of chrononutrition provides useful information on how we manage food intake across the day. The COVID-19 emergency, and the corresponding restrictive measures, produced an unprecedented change in individual daily rhythms, possibly including the distribution of mealtimes. Designed as a cross-sectional study based on an online survey, this study aims to assess the chrononutrition profiles (Chrononutrition Profile Questionnaire, CP-Q) in a sample of 1298 Italian participants, during the first COVID-19 lockdown, and to explore the relationship with chronotype (reduced Morningness-Eveningness Questionnaire, rMEQ), sleep quality (Pittsburgh Sleep Quality Index, PSQI) and socio-demographics. Our findings confirm a change in eating habits for 58% of participants, in terms of mealtimes or content of meals. Being an evening chronotype and experiencing poor sleep imply a higher likelihood of changing eating habits, including a delay in the timing of meals. Also, under these unprecedented circumstances, we report that the timing of breakfast is a valuable proxy capable of estimating the chronotype. From a public health perspective, the adoption of this straightforward and low-cost proxy of chronotype might help in the early detection of vulnerable subgroups in the general population, eventually useful during prolonged stressful conditions, as the one caused by COVID-19 pandemic.

Life before and after COVID-19: The 'New Normal' Benefits the Regularity of Daily Sleep and Eating Routines among College Students.

After the COVID-19 lockdown, a 'new normal' was established, involving a hybrid lifestyle that combined face-to-face with virtual activity. We investigated, in a case-control study, the impact of the 'new normal' on daily sleep and eating routines, compared with pre-pandemic conditions. To do this, we propose using social and eating jet lag as markers of the regularity in daily routines. Additionally, we studied whether the 'new normal' had an impact on the body mass index (BMI), diet quality, and other health-related variables. This study included 71 subjects in the pre-pandemic group, and 68 in the 'new normal' group (20-30 years). For all participants, we evaluated social and eating jet lag, BMI, diet and sleep quality, eating behaviors, physical activity, and well-being. General linear models were used to compare outcome variables between pre-pandemic and 'new normal' groups. The results revealed that the 'new normal' was associated with greater regularity in daily sleep and eating routines (-0.7 h of social jet lag (95% CI: -1.0, -0.4), and -0.3 h of eating jet lag (95% CI: -0.5, -0.1)), longer sleep duration on weekdays (1.8 h (95% CI: 1.5, 2.2)), and lower sleep debt (-1.3 h (95% CI: -1.7, -0.9)). Regarding BMI and other health-related variables, we observed that these variables were similar between 'new normal' and pre-pandemic groups. These findings indicate that the 'new normal' had a positive impact on daily sleep and eating routines. Additionally, our results indicated that the 'new normal' offered college students a more sustainable lifestyle, which was associated with more hours of sleep during the week and lower sleep debt. This, in the long run, could have a positive impact on BMI and overall health.

Meal and Sleep Timing before and during the COVID-19 Pandemic: A Cross-Sectional Anonymous Survey Study from Sweden.

The COVID-19 pandemic and related restrictions, such as stay-at-home-orders, have significantly altered daily routines and lifestyles. Given their importance for metabolic health, we herein compared sleep and meal timing parameters during vs. before the COVID-19 pandemic based on subjective recall, in an anonymous Swedish survey. Among 191 adults (mean age: 47 years; 77.5% females), we show that social jetlag, i.e., the mismatch in sleep midpoint between work and free days, was reduced by about 17 min during the pandemic compared with the pre-pandemic state (p < 0.001). Concomitantly, respondents' sleep midpoint was shifted toward morning hours during workdays (p < 0.001). A later daily eating midpoint accompanied the shift in sleep timing (p = 0.001). This effect was mainly driven by a later scheduled first meal (p < 0.001). No difference in the timing of the day's last meal was found (p = 0.814). Although our survey was limited in terms of sample size and by being cross-sectional, our results suggest that the delay in sleep timing due to the COVID-19 pandemic was accompanied by a corresponding shift in the timing of early but not late meals.

Early dinner or "dinner like a pauper": Evidence, the habitual time of the largest meal of the day - dinner - is predisposing to severe COVID-19 outcome - death.

COVID-19 and metabolic syndrome are devastating pandemics. Effective control of metabolic parameters and their dysfunction may help prevent or minimize the acute and devastating effects of SARS-CoV-2 by reducing the local inflammatory response and blocking the entry of the virus into cells. With such consideration in mind, we gathered data from dietary surveys conducted in nine European countries to explore the relationship between actual clock hour of the large dinner meal and also interval in minutes between it and sunset in the respective countries and death rate above the median rate of per one million people as an index of mortality due to COVID-19 infection. Clock time of the dinner meal varied between 16:00 and 21:00 h across the European counties sampled, and the correlation between dinner mealtime and death rate was strongly correlated, R = 0.7991 (two-tailed p = 0.0098), with R2 explaining 63% of the variation within the data. This strong linear positive correlation indicates that the later the clock time of the dinner meal, the higher is the death rate (and vice versa). The relationship between meal timing in reference to sunset, utilized as a gross surrogate marker of the activity/rest synchronizer of circadian rhythms, and death rate was negative and even slightly stronger, R = -0.8025 (two-tailed p = 0.0092), with R2 explaining 64% of the variation within the data. This strong linear negative correlation indicates that the shorter the interval between the dinner meal and sunset, i.e., the closer the time of the largest meal of the day to bedtime, the greater is the death rate (and vice versa). Our preliminary approach to nighttime eating, in terms of the day's largest caloric intake, as a risk factor for the predisposing conditions of obesity, metabolic syndrome, type 2 diabetes, and other commonly associated comorbidities of being overweight, and death from COVID-19 infection reveals strong correlation with the time of the dinner meal, both in terms of its actual clock and circadian time.