Abstract
Background
Nurses have high rates of overweight and obesity, and physical inactivity is one key determinant of weight gain.
Aims
The present study aims to quantify nurses’ energy expenditure over a standard 12-hour shift to establish whether activity levels at work are too low to maintain a healthy body weight.
Methods
Ward-based nurses (n = 96, 90 female, mean age = 36 years, mean experience = 10 years, mean body mass index = 26.6) wore heart rate and physical activity monitors for the duration of one full working shift. Heart rate and activity data were used in combination with demographic information to estimate each nurse’s energy expenditure over 12 hours.
Results
On average, nurses burned 2.12 kcals per minute while at work, equating to 1521 kcals/6364 kJ (SD = 403 kcals/1686 kJ) per 12-hour shift. Energy expenditure over 12 hours varied markedly between nurses (from 812 kcals/3397 kJ to 3005 kcals/12,573 kJ) but was sufficient in 72% of participants (assuming minimal resting levels of energy expenditure for the 12 hours not at work) to burn off a daily calorie intake of 2000 kcals.
Conclusions
Three-quarters of nurses expend more energy on working days than is required to maintain a healthy body weight if dietary intake does not exceed recommended levels.
Introduction
As many as 69% of registered nurses in the United Kingdom (UK) are overweight or obese (Kyle et al., 2016), a statistic that is higher than elsewhere in the world (Bogossian et al., 2012; Coomarasamy et al., 2014; Han et al., 2011; Zapka et al., 2009). Obesity is associated with an increased risk of a wide range of health conditions including diabetes, cancer, heart disease, musculoskeletal disorders and psychological ill health (World Health Organization, 2018). Consequently, nurses with a higher body weight are more likely to take sickness absence from work (Goetzel et al., 2010), contributing to organisational issues such as reduced staffing and related reductions in the quality of patient care (Jafar Jalal et al., 2014; Schulte et al., 2007).
Despite expert health knowledge and a comparable physical working environment to other healthcare workers, nurses appear to be more vulnerable to weight gain than other health professional groups (Kyle et al., 2016, 2017). Studies exploring why nurses are more likely to gain weight typically focus on eating behaviour, finding higher consumption of calorific foods (e.g. sweet foods and snacks; Hoppe and Ogden, 1997) to be associated with work-related factors such as stress and tiredness (Torquati et al., 2016), lack of regular breaks (Torquati et al., 2016), shift patterns (Marquezea et al., 2012), food gifts from patients (Cheung, 2003) and the influence of work colleagues (Persson and Martensson, 2006; Phiri et al., 2014).
However, weight gain is typically a product of both excess energy intake (eating) and insufficient energy expenditure (physical inactivity), yet relatively little research has investigated nurses’ activity levels. Most physical activity research relating to nurses focuses on leisure time activity and indicates that nurses do not typically meet physical activity guidelines (Ahmad et al., 2015; Blake and Harrison, 2013; Blake et al., 2011; Jung and Lee, 2015; Naidoo and Coopoo, 2007) and have low–moderate average leisure-time activity levels (Albert et al., 2014; Nahm et al., 2012; Perry et al., 2015; Tucker et al., 2010). Importantly, however, nursing is, at least anecdotally, an active and physically demanding job with long working hours, so it is possible that nurses are less active in their leisure time as they have already been highly physically active at work.
A recent systematic review found only one study in the literature that had set out to measure nurses’ physical activity at work, along with 14 studies that included some measure of activity during shifts (Chappel et al., 2017). Studies differed markedly in the methods used to capture activity level (from heart rate monitoring to self-reported estimates), but the majority concluded that nurses spent most of their shifts engaged in light-intensity activity only (Chen et al., 2011; Hui et al., 2001; Irimagawa and Imamiya, 1993; Nicoletti et al., 2014; Nuikka et al., 2001; Schall et al., 2016; Takahashi et al., 1999; Wakui, 2000). Four studies found nurses to be moderately active, but two of these were conducted with nurses working outside of the typical hospital environment (Babiolakis et al., 2015; Chen et al., 2014; Irimagawa and Imamiya, 1993; Makowiec-Dabrowska et al., 2000). Importantly, none of these studies were carried out in the UK, and there are likely to be substantial differences in the organisational structures and systems that dictate the nature of nursing work from one country to the next.
UK nurses are estimated to spend a substantial amount of time completing paperwork and (often sedentary) clerical tasks (Royal College of Nursing, 2008), leading to concern that highly skilled nurses have less time for direct patient care (NHS Institute for Innovation and Improvement, 2012). Observational studies support this to some extent, finding that nurses spend only around a third of their time on direct patient care, with the remainder spent on other, potentially less active, tasks such as documentation, preparing medication, reviewing results, retrieving information and professional communication (Farquharson et al., 2013).
Nurses’ relatively low activity levels at work are one potential determinant of weight gain as they spend a substantial proportion of their waking hours at work and leisure-time activity is typically low. The present study aimed to quantify nurses’ energy expenditure over a standard 12-hour shift to establish whether their physical activity levels at work are high enough to help maintain a healthy body weight.
Methodology
Study design
Real-time, ambulatory data on nurses’ physical activity and heart rates were collected as part of a larger, observational study on nursing tasks, stress and performance in 2012. Full details of the parent study protocol are available elsewhere (Farquharson et al., 2013), but in brief, as part of a larger study protocol (involving regular diary reports of current tasks and stress levels), ward-based nurses were asked to wear heart rate and physical activity monitors for the duration of two full working shifts. The present study uses this heart rate and activity data to calculate energy expenditure for each participating nurse.
Participants and setting
All nurses working on medical or surgical wards with more than 20 beds in a large UK teaching hospital were invited to participate in the study. Of those invited, 100 consented to take part, and continuous physical activity and heart rate data were available for 96 individuals (90 female, mean age = 36 years, mean experience = 10 years, mean body mass index = 26.6). The sample was comparable to all nurses working on wards in the hospital under study in terms of average age and years of experience (36.9 and 11.0 years respectively).
Measures
The main study outcome variable was energy expenditure over a working shift. Energy expenditure was calculated from a combination of manually entered demographic information (gender, age and body weight) and from heart rate and physical activity data that were continuously recorded over one full work shift using an Actiheart monitor. The Actiheart (CamNTech) is a compact, lightweight (<10 g) heart and physical activity monitor that clips directly to two adhesive chest electrodes. Mean acceleration, heart rate, inter-beat intervals and heart rate variability were stored in 15-second epochs and time and date stamped. The monitor has been validated for use in ambulatory participants (Brage et al., 2005).
Procedure
Nurses who indicated an interest in the study were sent an information pack and consent form and asked to nominate two upcoming work shifts where they would be engaged in typical activities (not non-standard activities such as training) for participation in the study. A study researcher met participating nurses immediately before each nominated shift to attach the Actiheart monitor. Nurses wore the monitor for the full duration of each of the two nominated participation shifts. Monitors were retrieved at the end of each shift, and the data downloaded from the device and subjected to the standard multi-stage Actiheart routine for removing artefactual data. Specifically, all inter-beat intervals of 2000 ms or more (indicating a missed beat) were rejected, as were beats that differed from the preceding beat by more than 20 × the average difference. The last 16 good inter-beat intervals were averaged and any outside +/−25% of this average removed. The remaining inter-beat intervals were then re-averaged and converted to beats per minute. Finally, all 1-minute means of < 40 bpm or > 170 bpm were removed. The data were good quality and only 0.01% of 1-minute means were rejected. Each participant’s data were then run through the Actiheart software’s in-built Advanced Energy Expenditure analysis procedure, which calculates energy expenditure over designated periods using group calibration co-efficients and branch parameters from the device validation study (Group Cal JAP, 2007).
Analysis
Data were descriptively summarised to estimate total energy expenditure. As participating nurses worked shifts of different lengths, energy burned per minute was calculated in kcals and kjoules and then scaled up to represent energy expenditure over a prototypical 12-hour shift to allow like-for-like comparison between individuals. Multi-level modelling was then used to investigate patterns in energy expenditure over the working day and to examine differences in energy expenditure related to key demographic factors: age, years of experience, work location and body weight.
Results
Demographic characteristics of the sample.
Energy expenditure over a standard 12-hour shift
On average, participating nurses burned 2.12 kcals/8.87 kJ per minute while at work, equating to an average of 1521 kcals/6364 kJ (SD = 403 kcals/1686 kJ) per 12-hour shift. Although the energy burned per minute (2.12 kcals/8.87 kJ) equates to ‘light intensity’ activity (<3 Metabolic equivalents or METs; Ainsworth, Haskell, Whitt, Irwin, Swartz et al., 2000), the total energy expended in a 12-hour shift is roughly equivalent to someone working in ‘moderate activity’ of 3 METs for 8 hours.
As illustrated in Figure 1, although mean energy expenditure was 1521 kcals/6364 kJ per 12-hour shift, calories burned by different individuals over a shift ranged from 812 kcals/3397 kJ to 3005 kcals/12,573 kJ. Energy expenditure was not recorded during leisure time in the present study, but even if participants spent the 12 remaining non-work hours asleep or totally sedentary, an average-weight (150 lb/10 stone 10 lbs) woman would be expected to burn approximately a further 63 kcals/264 kJ an hour or 756 kcals/3163 kJ. Adding this minimal baseline energy expenditure to the estimates of energy expenditure recorded during the work period indicates that 72% of participating nurses would be active enough on a work day to burn off the recommended (female) daily calorie intake of 2000 kcals.
Average energy expended (kcals) over a prototypical 12-hour shift.
Energy-expenditure patterns over the working day
Multi-level analysis determined that although patterns of energy expenditure varied between individuals, in general energy expenditure followed a cubic trend over the work shift. As shown in Figure 2, the amount of energy expended rose initially after coming on shift, then dropped mid-shift before climbing again and peaking towards the end of the shift.
Average pattern of energy expenditure (kcals per minute) over the work shift.
Energy expenditure and demographic factors
Energy expenditure in kcals per minute at work was unrelated to nurses’ age (beta weight = 0.005, p = 0.358), grade/seniority (grade 5 = 2.10, grade 6 = 2.16, grade 7 = 2.30, p = 0.606) or ward type (medical versus surgical; 2.191 versus 2.034, p = 0.153) but was significantly higher in nurses with higher body mass indices (BMI; beta weight = 0.068, p < 0.001). This greater energy expenditure in nurses with a higher BMI is not due to a higher activity level (nurses with a higher BMI are slightly but not significantly less active than others; beta weight = −0.159, p = 0.137), but rather to higher average heart rate and greater physical effort required during activity (beta = 0.901, p = 0.001), which leads to greater energy expenditure.
Discussion
Of 96 ward-based nurses studied continuously for a full working shift, 72% were expending enough energy to burn off food consumption of 2000 kcals a day. Average energy expenditure per 12-hour shift in the present study (1521 kcals/6364 kJ) was comparable to previous estimates from studies of physical workload and stress in nurses in the United States (1454 kcal per 12 hours; Chen et al., 2011), indicating that ward-based nurses engage, on average, in light to moderate activity across the working day. This is broadly in line with literature demonstrating that although nurses often walk long distances in the course of their jobs (Welton et al., 2006) and may have to complete physically demanding tasks, this is balanced out by spending a considerable amount of time on tasks that are less active (e.g. documentation, professional communication and so on; Farquharson et al., 2013).
Given the high rates of obesity and overweight in the nursing population, there has been increased interest in the development and implementation of weight management interventions for this group. The present results demonstrate that most nurses (a predominantly female workforce) are active enough on work days to burn off the recommended daily calorie intake for women (2000 kcals), which suggests that any workplace-based weight interventions aimed at nurses may be better focused on reducing dietary intake than on increasing activity levels while on shift (e.g. with workplace walking groups). Although many weight management interventions designed specifically for nurses are targeted at the workplace (Chan and Perry, 2012; Power et al., 2014), there is currently little evidence to suggest that unhealthy behaviours are more likely to occur within (as opposed to outside of) the workplace. In fact, it is possible that nurses are more likely to engage in unhealthy behaviours in the hours after coming off shift than during the working day. Although the present study did not test this directly, it will be vital for the development and appropriate targeting of weight-loss interventions for nurses that future research pinpoints when, where and why nurses are most likely to consume unhealthy foods or be inactive.
Qualitative data in this population suggest that nurses may be particularly likely to eat unhealthy convenience foods and engage in sedentary behaviours after coming off shift and/or in days off following busy or stressful shifts (Power et al., 2017) and that ‘self-licencing’ (i.e. the tendency to engage in behaviours perceived as ‘bad’ on the basis that one has recently done something ‘good’; De Witt Huberts, 2014) may play a role in overconsumption and inactivity on days off work. Future studies should investigate patterns of activity over full 24-hour periods and over multiple days to determine when and where nurses are most likely to be inactive.
The present study has a number of strengths and limitations. Energy expenditure was estimated from objectively and continuously measured heart rate and physical activity, removing any bias that would be associated with self-report measures. There were very few missing data and the sample of nurses who participated was representative of the wider nursing workforce in terms of their demographic characteristics. However, simply wearing activity monitors may have prompted nurses to be more active (the Hawthorne effect), and nurses who volunteered to participate may have been more active than those who did not, potentially leading to an overestimation of activity level. In contrast, physical activity outside of working hours was not directly measured and was instead estimated at a minimal (sedentary) level, so total energy expenditure over 24 hours is likely to be higher than estimated here. The latter underestimation would not change our conclusions (as higher levels of energy expenditure would make it even more likely that activity levels are sufficient to maintain a healthy body weight) but should be noted. Furthermore, although the objective measures used in the current study give a well-controlled estimate of energy expenditure, accounting for nurses’ age and weight, it should be noted that true energy expenditure will also be influenced by several unmeasured factors (such as temperature, physical fitness etc). Finally, as weight loss and maintenance of a healthy body weight depends on energy balance, future studies should aim to simultaneously assess both energy expenditure and intake.
In terms of implications for policy and practice, the present results suggest that workplace health initiatives should look at patterns of energy expenditure and intake both within and outside of the working environment to understand and address the factors producing weight gain in the nursing population.
Conclusion
Most nurses expend enough energy on working days to maintain a healthy weight if dietary intake does not exceed recommended levels. Further studies are needed to investigate nurses’ eating and activity patterns in real time, both at work and at home, to determine how best to target healthy weight interventions.
Key points for policy, practice and/or research
Nurses expend on average 1521 kcals/6364 kJ over a 12-hour shift. 72% of nurses expend enough energy to maintain a healthy body weight if dietary intake does not exceed recommended levels (for females). Most studies of eating and activity level in nursing focus on the workplace, and more comprehensive studies of when and where unhealthy behaviours occur are required.
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Ethics
The present study was approved by the NHS North of Scotland Research Ethics Committee (reference 10/S0801/87).
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship and/or publication of this article: These data were collected as part of a Scottish Government Chief Scientist Office funded study (CZH/4/460). Julia Allan is currently (2018) an Royal Society of Edinburgh (RSE) sabbatical grant holder.
