Deviant eating behavior such as skipping meals and consuming unhealthy meals has a significant association with mental well-being in college students. However, there is more to what an individual eats. While eating patterns form a critical component of their mental well-being, insights and assessments related to the interplay of eating patterns and mental well-being remain under-explored in theory and practice. To bridge this gap, we use an existing real-time eating detection system that captures context during meals to examine how college students’ eating context associates with their mental well-being, particularly their affect, anxiety, depression, and stress. Our findings suggest that students’ irregularity or skipping meals negatively correlates with their mental well-being, whereas eating with family and friends positively correlates with improved mental well-being. We discuss the implications of our study in designing dietary intervention technologies and guiding student-centric well-being technologies.

Food, Mood, Context: Examining College Students’ Eating Context and Mental Well-being

Shift-work is increasingly common in society and is associated with a number of health inequalities. The health effects of shift-work can include a redudion in quality and quantity of sleep, insomnia, chronic fatigue, anxiety and depreSSion,decreased vigilance, metabolic syndrome, adverse cardiovascular (especially blood pressure), gastrOintestinal effects and reproductive effects in women. Shift-work is also associated with disturbances to a workers domestic and social life. Physical activity is known to either prevent or alleviate these health inequalities in those with 'normal diurnal' lifestyles such as day-workers. However, shift-work generally decreases opportunities for physical adivity. Moreover, the favourable affects of physical activity on such health inequalities have not been confirmed in shift-workers. The studies in the present thesis are designed to examine the associations between shift-work and physical activity covering a wide range of physiological and psycho-social variables in shift-workers. The first descriptive study was designed to provide the first detailed and multi-researchstrategy examination of LTPA and its correlates in shift-workers. One hundred and sixty one shift-workers partiCipated in the initial cross-sectional study. A cohort of ten of these partiCipants also volunteered for further diaryand inteNiew-based studies. PartiCipants completed the SSI together with a LTPA questionnaire. Gender, job type, age and shift-work experience were explored as correlates of LTPA. The cohort also completed a 7-day diary and wore an accelerometer for assessment of activity counts during work, leisure, and bedtime when working each shift-type (days, nights and rest). Participants also completed a semi-strudured email-administered interview. The total energy expenditure per week in LTPA of male shift-workers was found to be twice that of women. Midwives recorded the lowest LTPA. Firefighters reported the most LTPA. The time spent out of bed during night shift days was 4-h higher compared with rest days. Data from this study indicated that LTPA is generally low amongst shift-workers, the majority of whom are overweight or obese. Jobtype and gender are much more influential on LTPA than age or experience. Shift-workers spend more of their time on rest days in bed. The second descriptive study was designed to explore the relationships between coping strategies adopted by shift-workers and their leisure-time energy expenditure. The importance of coping strategies has been highlighted in previous research. Ninety-five participants completed an adapted version of the completed the SSI together with a LTPA qUestionnaire. Predictors of age, time spent in shift-work, gender, marital status and the various shift-work coping indices were explored with step-wise multiple regression. Leisuretime energy expenditure over a 14-day period was entered as the outcome variable. Gender (p <0.023) and time spent in shift-work (p <0.051) were found to be predictors of energy expenditure, with the most experienced, male shift-workers expending the most energy during leisure-time. Overall 'disengagement' coping scores from the SSI were positively related to leisure-time energy expenditure (p <0.054). In males, disengagement of sleep problems (p >0.086) was found to be negatively correlated to energy expenditure, whereas disengagement of domestic-related problems was found to be positively related to energy expenditure (p <0.001). These relations were not found in female shift-workers (p >0.762). These data indicated that experienced male shift-workers participate in the most leisure-time physical activity. These people 'disengage' more from their domestic-related problems, but less from their sleep-related problems. The next laboratory-based study was designed to examine the acute effects of evening exercise and meal frequency on psychophysiological and performance-related variables during a subsequent period of simulated night-work. Nine healthy participants, completed at least two crossover trials beginning at 18:00 h. Between 19:00-20:00 h, participants either rested or exercised at 50%V02peak and then remained awake throughout the night, completing various tasks until 05:15 h. Six participants completed a total of four trials in which they exercised or rested while either one standardized (SOkJlkg) meal at 22:00 h or two smaller (30 kJ/kg) meals at 22:00 and 02:00 h were eaten. Core Body Temperature (Tc), wrist activity, mood, sleepiness, arousal, self-chosen work-rate, and reaction time were all measured throughout the simulated night-shift. Following exercise, Tcwas Significantly lower throughout the night-shift compared with no prior exercise (95% Cl = 0.00 to 1.01°C), even though wrist activity was higher and sleepiness was lower after exercise. Self-chosen workrate was significantly higher (95% Cl = 20 to 43 W) and reaction time faster during the nightshift that followed exercise. Reaction time and alertness were worst when only 1 meal was ingested during the night-shift (p <0.04). These data indicate that a single bout of evening exercise can improve sleepiness as well as mental and physical performance during a subsequent simulated night-shift. The second laboratory-based study was designed to investigate the acute effects of exercise on BP monitored during simulated night-work. Nine normotensive participants, completed at least two crossover trials beginning at 18:00 h. Between 19:00-20:00 h, participants either rested or exercised at 50%V02peakand then remained awake throughout the night, completing a variety of tasks until 05:15 h. Six participants completed a total of four trials in which they exercised or rested while either one standardized (60 kJlkg) meal at 22:00 h or two smaller (30 kJlkg) meals at 22:00 and 02:00 h were eaten. Systonc and diastonc BP, mean arterial pressure (MAP), heart rate and wrist activity were recorded every 30 min. Following exercise, MAP was Significantly (p <0.0005) lower throughout the night-shift compared with no prior exercise (95% confidence limits for reduction: 4 to 7 mmHg). The post-exercise reductions in systolic BP and MAP were not moderated by diet, but the reduction in diastolic BP was slightly greater when only one meal was eaten (p <0.0005). BP was lower even though wrist activity and heart rate were Significantly higher following exercise (p<0.0005). These data indicate that prior exercise lowers BP throughout a subsequent a-hour night-shift in healthy individuals within the normotensive range. Therefore, regular low-intensity exercise might moderate the well-known association between shift-work partiCipation and raised BP. The final fteld-based intervention study was designed to determine using a 12-week randomised controlled trial, the effect of physical activity and dietary centred motivational interviewing (Mf) upon blood pressure, stress and quality of life. Forty-four participants were involved in the trial. Twenty-one participants were assigned to the intervention group and received MI. SystOliCand diastolic BP, mean arterial pressure (MAP), perceived stress (PSS) and quality of life (QOL) were all monitored. Thirty participants completed the trial. No significant differences between experimental groups were present with respect to S8P, DBP, MAP or HR (p>0.2S, p>0.24; p>0.48 and p>0.8S) respectively). PSS scores were Significantly lower at study week 13 in the intervention group (p<0.05; 95% Cl =7.7-20.S). Over the course of the study, the intervention group also had a Significantly positive increase in QOL scores (p<0.05; 95% Cl =78.1-87.1). There were no Significant differences between groups in relation to physical activity. In this population, a 12-week MI intervention which focused upon increasing physical activity level and improving dietary habits significantly reduced workers perceived stress and increased the perception of quality of life, but not blood pressure or LTPA. MI focussing upon lifestyle factors may be a useful strategy for tackling stress, perceived quality of life and potentially cve in shift-workers. The findings from the studies in this thesis indicate that many of the short-term health benefits of exercise are apparent in contexts of shiftand night -work. The relatively small final intervention study demonstrates the potential utility of an individualised lifestyle intervention based on motivational interviewing for shift-workers.

Behavioural and biological relationships between leisure-time physical activity and health outcomes during shift- and night-work

A variety of organisms including mammals have evolved a 24h, self-sustained timekeeping machinery known as the circadian clock (biological clock), which enables to anticipate, respond, and adapt to environmental influences such as the daily light and dark cycles. Proper functioning of the clock plays a pivotal role in the temporal regulation of a wide range of cellular, physiological, and behavioural processes. The disruption of circadian rhythms was found to be associated with the onset and progression of several pathologies including sleep and mental disorders, cancer, and neurodegeneration. Thus, the role of the circadian clock in health and disease, and its clinical applications, have gained increasing attention, but the exact mechanisms underlying temporal regulation require further work and the integration of evidence from different research fields. In this review, we address the current knowledge regarding the functioning of molecular circuits as generators of circadian rhythms and the essential role of circadian synchrony in a healthy organism. In particular, we discuss the role of circadian regulation in the context of behaviour and cognitive functioning, delineating how the loss of this tight interplay is linked to pathological development with a focus on mental disorders and neurodegeneration. We further describe emerging new aspects on the link between the circadian clock and physical exercise-induced cognitive functioning, and its current usage as circadian activator with a positive impact in delaying the progression of certain pathologies including neurodegeneration and brain-related disorders. Finally, we discuss recent epidemiological evidence pointing to an important role of the circadian clock in mental health.

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It’s About Time: The Circadian Network as Time-Keeper for Cognitive Functioning, Locomotor Activity and Mental Health

Background: The aim of this study is to find a pathway to explaining the relations between dietary behaviors with mental health and psychological functioning. Materials and Methods: This cross-sectional study contains 4763 participants from the employees of Isfahan University of Medical Sciences. In this study, four questionnaires were administered which were provided as follows: demographic characteristics, 21-item dietary behaviors questionnaire, Hospital Anxiety and Depression Scale questionnaire, and 12-item General Health Questionnaire (GHQ-12). We started the analysis with the structural equation modeling (SEM) model with 4 unobserved latent and 16 observed variables. Results: The results show that the regression coefficient (standard error) of diet behavior on mental health and mental health on GHQ were − 1 (0.37) and 0.02 (0.01) with their P values as 0.007 and 0.01, respectively. For this model, the estimated root mean square error of approximation is 0.062 with 90% confidence interval of (0.060–0.065). In addition, the comparative fit indices (CFIs) were as 0.866 for incremental fit index and 0.866 for CFI. All these indices represent fairly good fit of the model to the data. Conclusion: We can conclude that “lower scores on diet behavior – higher scores on mental health problems” and “higher mean scores in depression and/or anxiety – higher scores in GHQ domains.” The SEM results showed that dietary behaviors have significance related to depression and/or anxiety and general health status.

The mediating role of Mental Health in the relations between dietary behaviors and General Health

An increasing amount of people have their work hours displaced to the night and there are indications that shift work and other irregular working schedules are associated with an increased risk of developing the metabolic syndrome and other pathological conditions. It is therefore important to address the consequences of eating at irregular hours, especially nighttime. Papers I-III refer to a study in which 7 males were given a high-carbohydrate diet (HC) or a high-fat diet (HF), using a cross-over design. Subjects were kept awake for 24 h and food was provided as 6 equally spaced isocaloric meals. Higher energy expenditure and non-esterified fatty acids (NEFA) concentration, as well as lower glucose and triacylglycerol (TAG) concentrations were observed with the HF-diet, compared to the HC-diet. With the HF-diet, fat oxidation, heat release, heart rate, glucose, NEFA and TAG concentrations differed depending on time of day. The highest postprandial TAG concentrations were seen after the 04.00 meal with both diets. Insulin and leptin responses to meal intake differed with respect to diet and time of day. Time of day affected glucagon, thyroid stimulating hormone, free thyroxin, total triiodothyronine (tT3), cortisol, chromogranin A and pancreatic polypeptide (PP) concentrations. PP’s postprandial increase was greater during 08.00 – 16.00 compared to 20.00 – 08.00. Furthermore, the subjects felt less irritated when eating the HF-diet but hunger was not related to macronutrient composition. Hunger and thirst decreased throughout the 24 h period despite constant activity and energy intake; and were correlated with several endocrine and metabolic variables. In paper IV 7 males were studied twice during 24-h either given 6 isocaloric meals throughout the 24-h period, or 4 isocaloric meals from 08.00 to 20.00, followed by a nocturnal fast. Energy expenditure, glucose, TAG, insulin and glucagon concentrations were lower; and NEFA concentrations were higher during the nocturnal fast compared to nocturnal eating; although no 24 h differences between the protocols were apparent. The subjects were more passive during the fasting period compared to when food was given. Stepwise regression showed that correlations between metabolic variables and hormones differed between daytime and nighttime. The decreased evening/nocturnal responses of cortisol and PP to meal intake suggest that nocturnal eating might have health implications and that the body reacts unfavorably to nocturnal eating. Smaller meals around the clock, however, showed marginally better effects on postprandial TAG concentrations and mental energy compared to larger meals during daytime. Further studies (long term) are needed before dietary guidelines can be given to shift workers, especially regarding the impact of nocturnal eating on gastrointestinal response and cortisol.

Metabolic and Endocrine Responses to Nocturnal Eating

Over the past two decades, substantial research has been conducted to investigate the idea that alterations in short-term nutritional intake play a role in influencing cognitive behaviour and mood. A portion of this research has examined specifically the effect of meal intake on the performance of mental tasks and subjective feelings of mood. Results of this research indicate that a number of variables including the timing and nutritional composition of the meal, nutritional status, habitual patterns of feeding behaviour, beliefs about food, and the nature of the mental tasks, can influence the effects of meals on cognitive behaviour. For example, studies have demonstrated that breakfast intake generally is associated with an improvement in cognitive performance later in the morning, while lunch intake is associated with an impairment in mid-afternoon performance on mental tasks and more negative reports of mood. Intake of nutrients late in the afternoon appears to have a positive effect on subsequent performance on tasks involving sustained attention or memory. Although research has provided insights into the role of meal intake on cognitive behaviour and mood, there are a number of factors which remain to be studied. These include the interaction of age, gender, activity level, meal composition, personality factors, stress with the effects of meals on cognitive behaviour. Additionally, more work is needed on the time-course of short-term nutrient effects, and the effects of chronic changes in meal intake on behaviour.

D. Benton

Papers

Psychological effects of snacks and altered meal frequency. Discussion