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Relationships between body mass index, appetite regulation and physical activity during shift-work and night-work

Morris, C J (2010) Relationships between body mass index, appetite regulation and physical activity during shift-work and night-work. Doctoral thesis, Liverpool John Moores University.

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Abstract

Approximately 3.6 million individuals in the UK are involved in a type of shift-work which impinges on the normal nocturnal sleeping period. This prevalence has significance considering that shift-work is a risk factor for many health problems including cardiovascular disease, breast cancer, metabolic syndrome, obesity and gastrointestinal symptoms (e.g., constipation). These health inequalities are generally under-researched. Past studies have also focused on chrono-biological related reasons (e.g., exposure to light at night) rather than lifestyle factors. Physical activity is reported to be beneficial for many aspects of day-worker's health. However, there is a dearth of knowledge regarding the relationship between physical activity, adiposity and gastrointestinal symptoms in shift-workers. Thus, the aim of this thesis was to explore, using a multidisciplinary approach, the relationships between body mass index (8M I), appetite regulation, gastrointestinal health and physical activity during shift-work and night-work. In the first study (presented in Chapter 3), a cross-sectional study design was adopted to explore the relationships between 8MI, gastrointestinal symptoms and leisure-time physical activity (LTPA) in shift-workers. The data from this study indicated that the least active shift-workers had the highest mean 8MI, 73% of these workers being overweight or obese. Nevertheless, dose-response effects of LTPA on 8MI were not evident. A positive relationship was present between physical activity level and frequency of heartburn but not other digestive symptoms (e.g., diarrhoea). In the studies presented in Chapters 4 and 5, the effects of an acute bout of evening exercise upon appetite-related factors were investigated during a simulated night-shift. In Chapter 4, the protocol was characterised by a feeding schedule typically adopted by many shift-workers, Le. eating smaller but more frequent portions of food rather than one large meal. In contrast, the protocol in Chapter 5 was characterised by a feeding schedule designed to be more in line with what day-workers do during their work-period, i.e. eating one larger meal 3-4 h after the work period has started. Findings from Chapter 4 indicate that, unlike after diurnal exercise, circulating concentrations of acylated ghrelin and leptin during a night-shift are increased by prior evening exercise. However, hunger during the night-shift was unaffected by prior evening exercise in this study. In the subsequent experiment involving one large meal, nocturnal concentration of serum leptin was increased by exercise but there was little effect on plasma acylated ghrelin level. Again, night-shift hunger was unaffected by prior evening exercise. Taken together, these findings indicated that exercise mediates different effects on appetite-related hormones at night and that meal frequency is an important factor which regulates the response of acylated ghrelin, but not leptin. Despite the above findings, mean night-shift hunger was unaffected by evening exercise, regardless of meal frequency. This implies that a compensatory increase in food intake during the night-shift in response to prior exercise may not occur, thus supporting the notion that exercise can mediate a negative energy balance which might attenuate body mass gain in shift-workers. The study presented in Chapter 6 determined the within-subject correlations between factors that regulate appetite in the post-exercise period. This study explored how circulating levels of acylated ghrelin and leptin are controlled at night following evening exercise. The findings from Chapter 6 suggested that exercise related changes in plasma acylated ghrelin concentration are negatively correlated to those in circulating levels of glucose and insulin, but not those in non-esterified fatty acids (NEFA) or triglyceride. The aforementioned Significant correlations were not reported in daytime studies. Post-exercise alterations in serum leptin level were also found to be related to those in circulating levels of insulin but not those in glucose, NEFA or triglyceride. The exercise-related alterations in circulating level of acylated ghrelin, but not leptin were correlated with the changes in hunger during the post-exercise period throughout the night. In the study presented in Chapter 7, a randomised controlled trial was employed to examine the effect of altering (via motivational interviewing over a three month period) a shift-worker's physical activity and dietary habits on their adiposity and gastrointestinal symptoms. The findings presented in Chapter 7 indicate that a 12-week motivational interviewing intervention which focused upon increasing physical activity level and improving dietary habits significantly attenuated an increase in 8MI, but not waist-to-hip ratio or frequency of digestive symptoms in UK shift-workers. In summary, this thesis makes a significant contribution to the field of physical activity and shift-work. This thesis demonstrates that relationships between 8MI, appetite regulation, gastrointestinal health (l.e., heartburn) and physical activity do exist during shift-work and night-work.

Item Type: Thesis (Doctoral)
Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Date Deposited: 15 Mar 2017 11:26
Last Modified: 15 Mar 2017 11:26
URI: http://researchonline.ljmu.ac.uk/id/eprint/5955

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