Twelve months of intervention consisting of diet, physical exercise and cognitive behavioral training significantly decreased body weight, BMI, body fat percentage as well as hip and waist ratio compared to the reference group. However, there were no significant differences between the two groups over time in blood pressure and physical capacity. The interpretation and implications of these findings are discussed below. The findings were based on intention to treat analysis and the workplace intervention was completed by a large proportion (85%) of the targeted overweight female health care workers.
The workplace is suggested to be an efficient arena for weight loss interventions, because workplaces often represent a clustering of different socioeconomic groups and health-related conditions, like overweight and obesity. The present study supports the workplace may be an efficient approach to reach a high-risk group since 93% of the eligible employees were overweight or obese. Using the workplace as a platform for weight loss programs may promote a team spirit among the employees facilitating a sustained effort and long term weight loss [31
]. The participants tended to form groups at workplaces, often based on gender, educational backgrounds and interests, which makes group-based cognitive behavioral training easier. Moreover, the employees met on a daily basis during the intervention period, and tended to share meals and have opportunities to meet immediately after work for physical exercise or other weight reduction activities [33
]. The relatively low drop-out in our study compared to other studies [34
] supports that the abovementioned factors have strengthened the completion rate in our study-group and ought to be considered in future studies and workplace initiatives for reducing excessive overweight.
The observed decrease of about 6
kg in body weight, of more than 2 units in BMI and with almost 3 percent in body fat among the female overweight health care workers are in the high end of the range of results from previously reported worksite interventions [2
]. There were variations in the weight loss, but a substantial proportion of individuals completing the intervention had a weight loss of more than 10% of initial body weight (Figure ). These findings support that clinically relevant decreases in body weight may be attained with life-style interventions in an occupational setting. If life-style interventions were initiated at more workplaces, hopefully the prevalence of diseases such as obesity, diabetes and cardiovascular diseases would decrease in the future.
The present study design followed the recommendations from recent reviews of integrating diet, physical exercise and cognitive behavioral approaches in order to increase the probability of prolonged weight loss [4
]. The positive findings of this study after 12
months supports that the integration of these three initiatives seems to be effective for long-term weight loss. Although not tested in this study, the timing and adaptive focus on these three initiatives for long term weight loss may be of importance. The main aim of the intervention after the primary focus on diet in the initial part (3
months) was to maintain the weight loss. We previously reported that that weight loss after the initial three months of the intervention was 3.6
kg on average [14
]. However, participants continued on average to lose weight over the following 9
months. This observation supports the potential effectiveness in physical exercise and cognitive behavioral approaches for maintaining and even increasing weight loss. It is however, also possible, that the participants in the intervention group continued to use the dietary tools they had learned in the first three months of the intervention to achieve further weight loss, despite the encouragement to focus on weight maintenance alone.
With respect to physical exercise, our results show no differences in physical capacity (strength and aerobic fitness) between the intervention and reference groups. The main purpose of the physical activity was in our study to help reducing excessive body weight and maintain muscle mass and not specifically to increase physical capacity measures. The physical exercise was therefore not primarily designed for improving specific physical capacities, but merely for promoting energy expenditure in a varied and motivating manner. If the aim was to enhance VO2max, the physical exercise would contain more high intensive activities. This may be the main cause for the lack of effect on physical capacity even though muscle mass was maintained. Maintaining muscle mass has in Henriksen et al. 2012 been pointed out as a specifically important aspect of a successful weight loss program [37
]. Also the relative aerobic power in the present study did increase due to the lower body weight and the maintained absolute aerobic capacity. Regarding aerobic power the present results are in accordance with Atlantis E, 2006, although that study suffered from a large drop out and a generally low compliance partly explaining the limited effect on both BMI and physical capacity [38
After three months intervention, we found a significant larger decrease in blood pressure in the intervention group compared to the reference group [14
]. After 12
months, this difference was no longer significant. Many other studies have found blood pressure reductions following life-style based work-place interventions [36
]. The fact that we did not find this effect after 12
month suggests that the intensity or the compliance of the intervention was not strong enough with respect to physical activity and perhaps further measures should be taken to ensure progression and compliance in the physical training. It should be noted, however, that the blood pressure did decrease compared to baseline within the intervention group, but a concomitant non-significant decrease in the reference group precluded the difference between groups from being statistically significant.
Strengths and limitations
This one year study was conducted as a cluster randomized single-blinded controlled trial, with data undergoing an intention-to-treat analysis (ITT). In spite of this rather conservative approach, we were able to reveal significant effects on the primary and secondary outcomes. The adherence rate of the study was very high, with a drop out of only 15% after 12
months. A limitation in the study is that in the integrated multiple interventions, the importance of each of the elements cannot be evaluated. Accordingly, we have not assessed the exact adherence to the diet or the other elements in the intervention. The diet was individually adjusted so participants were instructed that they could have a higher intake than calculated if they felt the need and could exercise more in order to keep the aimed calorie deficit. Even though the cognitive part of the sessions closely followed protocol, we could not entirely control what participants brought up for question and therefore we cannot state, that all participants got the precisely same guidance, which of course may affect the outcome. A well-defined protocol was followed concerning the brief physical exercises during sessions, but there was a limitation in the lack of quantitative registration of physical training doses in leisure time. The training logbook was primarily used to facilitate the individual coaching and serve as a motivating factor and no useful quantitative data on physical training could be obtained from these records.
Significant reductions in systolic blood pressure after 12 months were found for both groups, and therefore no significant Intervention group* Test round effects was found. This may be caused by an inability to totally prevent contamination between the groups by the cluster randomization. Finally, the target group only consists of females and the results cannot be extrapolated to males. Concerning statistics, the power calculation reported in the clinical trial and therefore in this paper do not take into account clusters as a covariate in the statistical analyses. However, because of the very clear finding on body weight, we don’t see this as an important limitation for the interpretation of the results. The statistical power is an issue though, with respect to the secondary outcomes in this study. Several ANCOVA models were carried out for testing effects of the intervention on multiple outcomes. The risk for a chance finding may therefore be present. However, reducing the level of significance would substantially increase the risk for a type II error. This aspect ought to be considered when interpreting the results.
The study was not designed for being very cost effective, but to investigate if it’s possible to generate a long-term weight loss among overweight health care workers in a workplace setting. After finding such positive results, a next step is to generate a cost-effective study with the same aim. Therefore, we did not perform a cost-effectiveness evaluation of this study.