The main result of this workplace randomized controlled trial consisting of diet, physical exercise and cognitive behavioral training was a mean weight loss of 3.6 kg in the intervention group. In addition, a substantial effect was found for systolic and diastolic blood pressure with decreases of 7.5 and 5.4 mmHg, respectively. A remarkably large adherence was obtained with only seven out of 98 participants dropping out during the three-month intervention. The results will be discussed in more detail below.
Among the 105 female health care workers, 93% was overweight, showing that efficient weight loss programs are highly relevant as health promotion for this sector. To our knowledge, this is the first randomized controlled workplace intervention among health care workers with the specific aim to reduce body weight. One previous Danish workplace health promotion study among health care workers, consisting of 20 weeks with weight training, fitness training and advice on healthy living did not show any positive effects on body weight . In a non-randomized study by Rigsby and colleagues from 2009 among 454 female employees at a hospital and nursing home, eight weeks weight loss intervention in groups reduced mean body weight by 3.8 kg . Other workplace studies not specifically targeting health care workers but aiming at weight loss with intervention periods from 10 to 16 weeks have shown weight losses from 1.3 - 4.5 kg [42–45]. In comparison to these workplace studies targeting similar populations or using comparable intervention programs, the present study shows an equal or even larger effect. Also the decrease in blood pressure was in line with or even larger than reported in previous studies on weight loss and blood pressure .
The intervention consisting of diet, physical exercise and cognitive behavioral training during working hours one hour/week was shown to be very effective, generating a significant weight loss, decreased blood pressure and increased aerobic fitness after three months. These findings support the recommendations of combining these three initiatives for successful weight loss . However, the long-term effects of this combined intervention remain to be investigated.
The intervention was not able to increase muscle strength, indicating that no changes in muscle mass occurred. Increasing muscle mass was considered a means to further ease weight loss by raising resting metabolism. Therefore, 10 - 15 minutes per week of physical exercise seems insufficient if the aim is to increase muscle strength while simultaneously encouraging weight loss. However, it was sufficient to maintain muscle strength alongside the weight loss. Similarly, no increase in VO2 max was found. However due to the weight loss, the aerobic fitness being relative to the body weight was increased. The maintained physical capacity in combination with the reduction in body fat % indicates that the weight loss achieved during the intervention is primarily due to loss of fat tissue. The increased aerobic fitness may represent a functional benefit, decreasing the relative physical workload of the health care workers, and therefore their risk of cardiovascular disease .
Only seven participants dropped out during the three months intervention. The adherence rate was therefore higher than in most other weight loss studies at the workplace [48, 49]. The successful adherence may be due to a number of initial precautions taken. First, workplaces adopting this intervention study were obliged by contract to provide time for the intervention during working hours. Second, each of the seven intervention groups was, as far as possible, guided by a single instructor to personalise the interventions. Third, a close collaboration between managers ensured that obstacles for the intervention were quickly solved. In summary, the workplace approach is likely to explain the high adherence and therefore the positive results of the study. Other studies have pointed out that workplace-initiated weight loss programs promote a team spirit among the employees [50, 51]. The participants tend to form into particular groups at workplaces, often based on gender, educational backgrounds and interests, which makes group counseling easier. The participants see each other on a daily basis during the intervention period and tend to share meals and have opportunities to meet immediately after work for exercise . In the present study, employees without weight problems were also invited to take part in the intervention. Not excluding them from the intervention may have contributed to a positive team spirit regarding the initiative.
The present study was conducted as a cluster randomized single-blinded controlled trial. It was carried out at a workplace that enabled us to target a high-risk group and obtain a very high adherence. The results in this paper were tested using intention-to-treat analyses (ITT), where missing observations are carried forwards or backwards. In spite of this conservative approach, we were able to reveal significant effects on weight loss and related outcomes such as fat percentage, waist circumference and blood pressure.
For a weight reduction program, a three months perspective is a short time frame. This study showed strong results after three months, but the main aim of the project is to maintain the weight loss for a longer period of time. Maintenance of the improved bodyweight, blood pressure and aerobic fitness is well known to reduce the risk of chronic diseases such as cardiovascular diseases and Type 2 diabetes, which in turn may reduce the risk for sick leave . There was no observed effect on musculoskeletal pain after three months of the intervention. However, because weight loss will lower the mechanical load on joints and potentially improve work postures, it may have a positive effect on musculoskeletal pain in the long run.
A limitation in the study is the lack of quantitative registration of physical training doses in leisure time. The logbook was primarily used to facilitate the individual coaching and serve as a motivating factor. Another limitation is that in the integrated multiple intervention concept of this study the importance of each of the components cannot be evaluated. A four-armed design where each of the components as well as the combined concept is tested against a control group would have been ideal, but also unrealistic with the current resources and the workplaces available. A qualitative process analysis with focus group interview is another approach that would have been possible, but unfortunately not performed. Finally, the target group only consists of females and the results cannot be extrapolated to males. Concerning statistics, several ANCOVA models were carried out for testing effects of the intervention on multiple outcomes. The risk for a chance finding may therefore be resent. However, reducing the level of significance would substantially increase the risk for a type II error. This aspect ought to be included in the interpretation of the study results.