In this cRCT, no additional intervention effects were found on PA and fruit and vegetable intake. The total direct and indirect costs in the intervention and control condition were comparable, but the programme costs were slightly higher for the intervention condition compared with the reference condition.
In a meta-analysis, only small non-significant effects were found on PA [10
]. In addition, there is only low quality of evidence that workplace PA interventions significantly reduce body weight and BMI [17
]. However, another systematic review reported strong evidence of WHPPs on PA but inconclusive evidence concerning body weight [12
]. The different conclusions might be due to differences in type of interventions, study designs and analytical techniques (qualitative versus quantitative). A systematic review studying the effectiveness of worksite PA and nutrition programmes reported an increased programme impact in more structured and intensive interventions [18
]. In our study, participants could visit the website on their own discretion, making it a less structured and intensive intervention.
A plausible explanation for the lack of an intervention effect is the non-use of the programme and therewith a lack of contrast with the control condition. There were small to modest improvements over time in vigorous PA (only at 1-year follow-up) and vegetable intake (both at 1- and 2-year follow-up), but these did not differ between both groups. Furthermore, no improvements in health indicators were found. During the period in which the intervention group received monthly e-mail messages, there was a higher programme utilization compared with the control condition [40
]. However, still only a minority used the website. Many participants in the intervention group reported that they did not receive monthly e-mail messages (20%) or were uncertain (22%) if they did so, whereas these messages were sent. Throughout subsequent periods, participants in the intervention condition did not visit the website more often compared with participants in the control condition. The use of self-monitors as well as the use of asking questions was limited. Because of the low use of several intervention components, there was a lack of contrast with the control condition, with both groups having a health check and general information on the website. Although there is an increasing popularity of Internet delivered programmes, the use of such programmes is often low [7
]. Nowadays, there are more and more possibilities for interaction between providers and participants using Internet- and cell-phone-based interventions (e.g. [41
]). A higher level of interaction might help to increase programme adherence.
In a systematic review, the authors concluded that populations at-risk benefit most from behaviour change programmes in the workplace setting [16
]. In our study, a high percentage of participants already met the lifestyle recommendations at baseline. For the PA guideline, this is likely due to over-reporting on the IPAQ. Over-reporting is a general concern in the measurement of self-reported PA [42
]. With the majority already meeting the national guidelines, particularly for moderate to vigorous PA, there is only small room for improvement in the participating study population. However, when focussing on those participants not complying with the healthy lifestyle guidelines, there was only a modest positive intervention effect for fruit intake after 1 year.
Shain and Kramer [43
] have argued that health promotion programmes will only be effective in enhancing the health status of the workforce when the interventions attend to both individual and environmental influences. This is in accordance with the findings in a recent systematic review showing greater improvements in workplace interventions with an environmental component [17
]. In our study, the intervention took place in the workplace setting, but the setting did not comprise a major role in the intervention programme, lacking environmental components. With the ability to make use of natural social networks as well as shared environments, there are opportunities to include more organizational aspects in behavioural interventions in the workplace setting.
Since the intervention did not show any effects, no cost-effectiveness analysis was conducted. The economic analysis showed that the costs of the intervention programme were modest and comparable to the direct health care costs. However, the economic evaluation is driven by the indirect costs due to productivity loss (96%), which were much higher than the direct costs (4%). A limitation in the economic evaluation was the measurement of indirect costs, with a categorical variable for sickness absence. Furthermore, possible compensation mechanisms were not taken into account, leading to an overestimation of indirect costs.
Because companies from different branches participated in the study, there are no indications that the results are not generalizable to other workforce populations. Although the populations of the participating workplaces differ, no differences in website use were found between workers spending a major par of the day with computer work compared with workers with less or no computer work. However, there are other limitations in the study. As mentioned before, the measurement of sick leave is not optimal to make a cost evaluation. In addition, subjective productivity loss at work was measured, using a single item assessing work productivity during the previous regular workday, which does not take into account the expected fluctuations in productivity loss across workdays. Another limitation in the study was that weight was measured at baseline and after 24 months but self-reported at both follow-up measurements. Since at 24 months follow-up, weight was self-reported and measured, these two types of measurement could be compared. Both measures were highly correlated (r = 0.99, P < 0.001).