Degree Name

Doctor of Philosophy


School of Health and Society


The high prevalence of overweight and obesity among workers in the mining industry in Australia poses a significant public health risk. There is a high burden associated with overweight and obesity among this cohort of workers to both the employer and the worker in terms of productivity loss, absenteeism, presenteeism (attending work while sick) and increasing risk of chronic diseases such as diabetes, hypertension and cancer. Therefore, a workplace health promotion program was identified as important and worthy of further investigation. The aim of this thesis was to determine the feasibility and effectiveness of a one year workplace health promotion program that aimed to reduce the overweight and obesity rates, and to improve the hydration status of a cohort of workers in the mining industry.

A pre-experimental study was conducted to investigate the feasibility and effectiveness of a one-year workplace health promotion program to reduce the body mass index (BMI) and improve hydration status among participants. The results of this study showed that among study completers (n=83), 83.2% of participants were either overweight or obese (42.2% overweight and 41% obese) at baseline. After one year of the workplace health promotion program, 80.7% of participants were either overweight or obese (38.6% overweight and 42.1% obese) resulting in a 2.5% decrease in the overall overweight and obesity rates. There was an increase in the consumption of core foods, especially fruit intake, from a mean of 1.1 serves per day to a mean of 1.9 serves per day (P=0.0249), nearly meeting the Australian Dietary Guidelines and the Australian Guide to Healthy Eating of 2.0 serves per day. Reported physical activity improved in females from 303 MET minutes / day to 331 MET minutes / day (P=0.738) but decreased in males from 391 to 367 MET minutes / day (P=0.751). There was an improvement to the work environment at the mine site in terms of being a ‘health promoting worksite’. Specifically, the number of posters and signage about healthy nutrition, physical activity, smoking and alcohol increased throughout the year. Contents of the vending machines and refrigerators at the site were reviewed and an increased number of healthier options was included.

With regards to dehydration and heat stress, 73% of participants started their shift dehydrated. By the end of the one-year health promotion program, only 31% of participants started their shift dehydrated, an improvement of 58% from baseline. Correlation of hydration status of workers with potential risk factors such as age, gender, BMI, educational level, physical activity level and smoking status showed no significant correlation with any of these risk factors. There was no change in the reported average daily fluid consumption from baseline, suggesting underreporting as hydration status of participants improved. Among participants who were at risk of heat related illness (n=13), identified through a Basic Thermal Risk Assessment, the mean urine specific gravity (USG) was 1.021 (Range 1.010 to 1.027) pre-shift and 1.024 (Range 1.019 – 1.032) post-shift. Eight were dehydrated pre-shift and 12 were dehydrated post-shift. All 13 participants had at least two heat strain symptoms, namely headache and fatigue. Environmental temperatures during summer with no cloud cover indicated that these workers were at a high risk of heat related illness with the predicted heat strain (PHS) index predicting a core temperature of 38 degrees being reached within the first two hours of work following lunch break. Considering that workers still have to work for five hours after the lunch break, this finding is significant for these workers. Under these working conditions, hydration status plays a very crucial role in heat dissipation from the core of the body. This was clearly demonstrated as correlation of core body temperature with potential risk factors such as BMI, pre- and post-shift hydration status, fluids consumed during the shift and heat strain symptoms showed significant correlation for pre-shift hydration status only (P<0.05).

The findings presented in this thesis provide evidence that a long term workplace health promotion program at an open cut mine site is feasible and improved the control of overweight and obesity rates, hydration status and some aspects of lifestyle choices. The results suggest that tailored programs can be effective, when the nature of the workplace and workers are taken into consideration. In addition, this thesis also provides evidence that pre-shift hydration status is the key factor determining a worker’s susceptibility to heat stress, and should be addressed as a priority for any hydration management guideline for working in hot environments.

FoR codes (2008)

111705 Environmental and Occupational Health and Safety, 111712 Health Promotion, 111799 Public Health and Health Services not elsewhere classified



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.