The effect of breaking up sitting time on health markers and its implication for the workplace

Abstract

The primary aim of the work included in this thesis was to investigate the effects of breaking up sitting time on cardiometabolic risk markers and appetite. The three acute experimental chapters in this thesis sought to do this by examining postprandial concentrations of glucose, insulin, triglycerides, high-density lipoprotein, acylated ghrelin and total peptide YY. Additionally, subjective appetite, physical activity energy expenditure and energy intake were investigated. In study one, postprandial glycaemia was attenuated in young, healthy adult men when breaking up sitting every 20 min with 2 min moderate-intensity physical activity (PA) following a high glycaemic index breakfast, compared with an uninterrupted sitting condition. There was no attenuation in glucose observed if a low glycaemic index breakfast had been consumed, suggesting that in a metabolically healthy sample, breaking up sitting may only be beneficial when high glycaemic index meals are consumed. In study two, postprandial lipaemia was improved across an 8 h period when breaking up sitting every hour with a short, high-intensity PA bout compared with uninterrupted sitting. This strengthens the efficacy of short bouts of PA of a high-intensity as strategy to improve postprandial lipaemia. However, data from study one and three suggests that attenuating postprandial glucose or insulin may require more frequent breaks in sitting than hourly PA bouts. Studies two and three observed no changes in appetite regulating hormones. Despite this, there was a suppression in subjective appetite when participants engaged in hourly high-intensity PA bouts, suggesting that a minimum threshold of PA intensity is required to elicit these effects. However, despite moderate-intensity PA breaks in sitting not suppressing appetite, no compensatory responses were observed in appetite or energy intake, resulting in an acute relative energy deficit. These findings suggest that this type of activity regime could assist in weight management programmes. Study four sought to investigate the efficacy of a workplace cluster randomised controlled trial at reducing workplace sitting. The multicomponent intervention did not reduce workplace sitting time. However, time spent in prolonged sitting bouts (> 30 min) was reduced and stepping time increased. This was concomitant with reductions in waist circumference and an increase in fat-free mass, demonstrating that a low-cost, short-duration, multicomponent intervention can be effective in changing sedentary behaviour patterns in the workplace. Overall, this thesis adds to the current evidence examining the effects of breaking up sitting on postprandial cardiometabolic risk markers and appetite, in addition to demonstrating the efficacy of a short-term low-cost multicomponent intervention at reducing prolonged sitting in the workplace by using strategies similar to those examined in studies one and three. Chapter eight summarises the significance of the findings from all four experimental studies whilst synonymously highlighting future directions for research in this area of the field.

Date of Award	Dec 2019
Original language	English
Awarding Institution	University of Bedfordshire
Supervisor	Andrew Mitchell (Supervisor), Julia Fruer (Second supervisor) & Daniel Bailey (Other)