Iris Kanera

7 161 General Discussion much deviating from their own perceptions, since our previous findings (Willems et al., 2016) indicated no need for diet advice, possibly causing cognitive dissonance (Festinger, 1957). As a consequence, participants with a red MRA may have reduced this dissonance between their own unhealthy diet and the recommendations by changing one’s perception and attitudes concerning (the importance of ) a healthy diet or the credibility of the MRA instead of trying to change the unhealthy behavior. These outcomes confirm that the intervention fit well with the needs of early cancer survivors and that the tailoring (including the MRA) worked well. Even non-module users highly appreciated the intervention, possibly due to the provision of the MRA and other intervention elements, such as the news items and the user forum. The news items included videos of various health professionals discussing various cancer aftercare topics. Unfortunately, the use of the news items and the forum was not evaluated in detail, which might be a subject of further research. Part 3. Intervention effect evaluation In Chapter 5 and 6, we assessed whether the web-based KNW was effective in changing lifestyle behaviors in the short and long term. After six months, higher increases in moderate PA and vegetable consumption with small effect sizes (moderate PA: d = .25; vegetable consumption: d = .37) were found for the KNW. These effects did not remain significant after correction for multiple testing (for the other lifestyle behaviors) that might have been analyzed as too conservative (Type 2 error; Kanera et al., 2016b ). In Chapter 6, we evaluated whether the initial increases in moderate PA and vegetable intake were sustained after 12 months. As a result, a significant and clinically relevant intervention effect was observed for moderate PA among cancer survivors younger than 57 years of age with a medium effect size ( d = .59). Age was identified as the only moderator of the effect on moderate PA in Chapter 6 (Kanera et al., 2017). The 6-month increases in vegetable consumption were not sustained after 12 months. No significant main intervention effects were found for fruit, whole grain bread, and fish intake between groups, although there was some room for improvement. The lack of effect in these diet behaviors might be related, for example, to taste and regional traditions. In general, diet behavior is influenced by taste perception, and survivors might favor foods other than recommended in the KNW (Loper, La Sala, Dotson, & Steinle, 2015). According to breast cancer survivors, food choices can be related to cancer treatment issues and psychosocial distress (e.g., changes in taste, food cravings, and emotional distress; Vance, Campbell, McCargar, Mourtzakis, & Hanning, 2017). Similarly, no intervention effect was found on smoking cessation, probably due to a low number of smokers and a related power problem. Noteworthy, the likelihood of quitting was almost three times higher in the IC compared to the UC (Kanera et al., 2016b).