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44 M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51 six months later (T2), and at follow up one year after completing the program (T3). Concerning T2, the participants were not exactly tested at the end of their treatment, as this moment was different for each of them. Each time, height, weight, implicit and self-reported attitudes were assessed. For practical reasons, the first measurement was completed at the Department of Moving and Sports Science of Ghent University, whereas the second measurement was completed in the residential setting. For the one year follow up, the children were invited to the residential setting for a general check-up. Sixteen youngsters of the test group showed up. The other three were tested at home. All children were tested individually. The order in which the two EASTs were administered, was counterbalanced. The questionnaire was completed after both EASTs were conducted. Each EAST consisted of three different blocks. Before each task, the participant provided words for physical activities or foods that he/she really (dis)liked. Next, in a first practice block, these individually selected attribute words appeared randomly four times in a white colour on the screen. Participants were instructed to classify these words according to their valence as quickly and as accurately as possible, by pressing the m-(positive) or the q-(negative) key of an AZERTY keyboard, in order to learn an extrinsic association between a positive (negative) valence, and the left (right) key. In a second practice block, each target stimulus was presented in at least once in blue and once in green. In the food task 12 trials were presented, and in the activity task 24 trials. Half of the participants pressed the m-key in response to green words and the q-key in response to blue words; the others pressed the m-key in response to blue words and the q-key in response to green words. In this way, they learned an association between a key carrying a valence and a colour. Finally, each task consisted of four crucial test blocks in which a mix of target and attribute words were presented. The physical activity task contained four test blocks of 32 trials (14 white trials, 18 coloured trials) each; the food task contained four test blocks of 38 trials each (14 white trials and 24 coloured trials). The words had to be classified depending on valence (for white words) or colour (for green and blue words). Stimuli were always presented in a random order, whereby the mixed blocks did not necessarily alternate between target (coloured) and attribute (white) stimuli. The inter-trial interval was 400 ms. If the participant responded incorrectly, a red cross appeared for 400 ms on the screen and the next stimulus was presented. 2.5. Statistical analyses Analyses were carried out using SPSS 12.0 for Windows. The analyses of the EASTs took only the responses on the coloured test trials into account, whereby trials with an incorrect response were discarded (De Houwer, 2003). In line with Greenwald et al. (1998), reaction times (RTs) below 300 ms or above 3000 ms were recoded to 300 ms and 3000 ms respectively. All RTs were log-transformed. Also mean percentage of errors (PE) were analysed. On the selfreports, attitudes towards sedentary activities, moderate intense physical activity (PA), high intense PA, unhealthy food and healthy food were obtained by averaging the respective item scores. Evolutions in mean attitudes were calculated conducting Repeated Measures ANOVA's. The explaining variance of attitudinal changes during treatment for the decrease in overweight during treatment and at follow up was analyzed using covariate multiple regression analyses. 3. Results 3.1. Mean implicit and self-reported attitudes at baseline A 3 (word category: sedentary activities vs. moderate intense PA vs. high intense PA)×2 (extrinsic response valence: positive vs. negative) Repeated Measures ANOVA on the baseline reaction times of the physical activity task showed no significant effects, all Fsb2.85. Also the same 3×2 Repeated Measures ANOVA conducted on the baseline percentage of errors revealed no effects, all Fsb2.19. However, a 2 (word category: unhealthy vs. healthy food) ×2 (extrinsic response valence: positive vs. negative) Repeated Measures ANOVA on the baseline reaction times of the food task showed a significant main effect of valence, F(1, 18)=6.08, pb.05. This indicates that the participants were positive towards both healthy and unhealthy food, which was also found in the total group as described in Craeynest et al. (2005). No other effects were found, all Fsb1. Also the same 2 ×2 Repeated Measure ANOVA conducted on the percentage of errors, revealed no effects, all Fsb2.49. A three-level within factor (word category: sedentary activities vs. moderate intense vs. high intense PA) Repeated Measures ANOVA on the self-reported attitudes towards physical activity, showed a significant effect, F(2, 17)=5.54, pb.05. Post hoc paired sample t-tests showed that moderate intense PA was rated more positive than sedentary activities, t(18) =3.08, pb.01, and high intense PA, t(18) =2.61, pb.05. A two-level within factor (word category: unhealthy vs. healthy food) Repeated Measures ANOVA on the
Table 1 Mean and standardized (SD) reaction times (RT) and percentage of errors (PE) on physical activity (PA) and food trials as a function of word category and extrinsic response valence, at baseline (T1), after six months (T2) and at a one year follow up (T3) T1 T2 T3 RT PE RT PE RT PE M SD M SD M SD M SD M SD M SD Physical activity (PA) Sedentary+pos 861 229 7.89 8.09 716 127 6.14 6.11 638 110 10.09 10.96 Sedentary+neg 855 213 7.39 7.29 714 106 7.89 8.09 688 120 8.33 11.79 Moderate intense PA+pos 880 272 7.02 8.46 743 224 8.77 15.33 706 135 10.09 16.80 Moderate intense PA+neg 902 263 10.53 9.56 742 155 8.77 8.99 658 148 7.46 12.39 High intense PA+pos 814 207 8.77 8.55 746 217 12.72 14.27 679 167 7.89 8.99 High intense PA+neg Food 833 179 6.58 8.60 736 160 7.46 13.86 676 134 7.46 16.87 Unhealthy food+positive 843 255 8.96 8.37 737 172 9.65 7.49 685 105 8.33 8.33 Unhealthy food+negative 893 277 7.67 9.35 717 178 8.77 8.20 686 86 8.11 9.57 Healthy food+positive 841 261 7.67 8.85 707 168 9.65 9.11 687 150 7.02 7.49 Healthy food+negative 898 277 9.91 8.00 734 173 9.43 6.49 717 97 8.55 11.49 self-reported attitudes towards food, showed a significant effect, F(1, 18)=4.47, pb.05. A post hoc paired t-test revealed that the participants were more positive towards healthy food than towards unhealthy food, t(18)=2.12, pb.05. Implicit associations are presented in Table 1; self-reported attitudes are described in Table 2. Remarkably, the same Repeated Measures ANOVAs with the dropout participants vs. the remaining group included as between variable, revealed a significant main effect of group on the PA EAST, F(1, 36)=5.27, pb.05, and on the food EAST, F(1, 36)=6.25, pb.05, showing that the dropout group in general reacted faster than the remaining group (PA task respectively M=783 ms, SD=44 ms and M=843 ms, SD=51 ms; food task respectively and M=790 ms, SD=37 ms and M=831 ms, SD=44 ms), possibly due to the mean older age of the drop out group. Further, both groups did not differ on the self-report attitudes towards PA, all Fsb1, however, an intriguing interaction effect was found between both groups and their self-reported attitudes towards food, F(1, 36)=4.87, pb.05, indicating that at baseline the dropout group was more positive towards unhealthy food and less positive towards healthy food, than the remaining group. 3.2. Mean effect of the treatment on ABMI M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51 The mean total treatment time of the participants was almost eight months (M=7.89, SD=2.05). A Repeated Measures ANOVA with one three-level within factor (T1 vs. T2 vs. T3), showed a significant effect of time on ABMI, F(2, 17)=98.98, pb.001 (respectively T1: M=163.86, SD=14.97; T2: M=127.46, SD= 12.15; T3: M=130.21, SD= 16.43). Post hoc paired sample t-tests showed that the ABMI at baseline differed significantly from the ABMI at the end of the treatment, t(18) =13.50, pb.001, whereas the ABMI at the end of the treatment differed not from the ABMI at follow up, t(18)=1.07, ns. This indicated that the group of participants included in the present study became less overweight during the treatment, and that this decrease in overweight was maintained at follow up. Table 2 Mean and standardized (SD) self-reported attitudes towards different kinds of physical activity and food, evaluated on a scale ranging from −3to+3, at baseline (T1), after six months (T2) and at a one year follow up (T3) T1 T2 T3 M SD M SD M SD Physical activity (PA) Sedentary activities 1.34 0.99 1.70 0.97 2.00 0.54 Moderate intense PA 2.04 1.06 2.07 1.01 2.16 0.80 High intense PA Food 1.02 1.09 1.67 1.02 1.88 0.80 Unhealthy food 0.96 1.86 0.72 1.82 0.69 1.20 Healthy food 2.07 0.80 1.89 0.97 1.91 1.24 45
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