It is necessary to comment that a large number of statistical tests were carried out to answer the research questions, and this may increase the probability of chance findings. To overcome this problem the tests were hypothesis-driven. Nevertheless, adjustment to the level of significance should be considered when reviewing the results, i.e. those at p<0.01 are very unlikely to be chance findings due to the large number of statistical tests carried out.
(1) Women with a history o f dieting will react more negatively than non-dieting women to the changes in body weight and shape that occur during pregnancy.
Factor analysis was carried out on the dissatisfaction with the changes in weight, stomach, breasts, hips / thighs, and face variables in order to reduce the data as it was suspected that these variables were all related.
The method used in the factor analysis was :
1. A matrix of correlation coefficients was generated for all the variable combinations. The correlation coefficients within the matrix were greater than 0.3 indicating that the variables were indeed related to each other.
2. From the correlation matrix one factor was extracted, which was able to account satisfactorily for the correlations within the matrix. This factor represented dissatisfaction with the overall changes in weight and shape.
3. Factor rotation, to maximise the relationships between the variables and the factors, was unnecessary as only one factor was extracted.
4. Factor scores were calculated for each participant to represent individual dissatisfaction with overall changes in weight and shape.
The use of factor analysis is limited by small sample size. The Kaiser-Meyer-Olkin (KMO) is a measure of sampling adequacy which should be greater than 0.5 for factor analysis to proceed. In the present analysis the KMO figure came to 0.77 indicating that the sample was adequate for factor analysis. In addition, B artlett’s Test of Sphericity was checked and found to be non-significant (<0.001) which ruled out the possibility of the correlation matrix being an identity matrix.
Factor scores were calculated for each participant at both 20 and 34 weeks into the pregnancy. The mean factor scores (representing dissatisfaction with overall weight and shape changes) were: at 20 weeks, 0.53 (0.86) for dieters and -0.18 (0.9) for non dieters, and at 34 weeks, 0.55 (0.89) for dieters and -0.20 (0.97) for non-dieters.
Independent t tests were performed on these factor scores to examine whether a significant difference existed between dieters and non-dieters for dissatisfaction with overall weight and shape changes. The results indicated that dieters were more dissatisfied than non-dieters with the overall changes that occurred in their weight and shape at both 20 weeks (t=3.24, 97df, p<0.01) and 34 weeks (t=3.17; 79df; p<0.01).
To identify exactly where differences existed a two (dieters vs non-dieters) by two (ratings of satisfaction: dissatisfied v satisfied / neither) chi-square analysis was performed for each change (weight; stomach; breasts; hips/thighs; face) at both time points in the pregnancy. Tables 11 and 12 present the results of this analysis together with the percentage of dieters and non-dieters that were dissatisfied with the changes in their weight and shape.
Table 11 : Dieters and Non-Dieters Dissatisfaction with the Changes in Their W eight and Shape at Twenty W eeks.
Dissatisfied W ith Changes In :
Dieters Non-Dieters Difference
Weight 26.6% 2.5% r^=l5 19;df= l;p< 0.001
Stomach 24.1% 10.1% X^=3.48; d f= l; ns
Breasts 41.3% 20.2% X^=4.92; d f= l; p<0.05
Hips/Thighs 60.7% 20.8% % ^=15.19;df=l;p<0.001
Face 14.8% 13.3% %^=0.03; df=l;ns
The analysis demonstrated that dieters were more dissatisfied than non-dieters with the changes that occurred in their weight, breasts, and hips/thighs at 20 weeks into the pregnancy. (These differences are illustrated in figures 1 to 3.) However, dieters and non-dieters did not differ significantly in their satisfaction with the changes that took place in their stomach and face.
3. Factor rotation, to maximise the relationships between the variables and the factors, was unnecessary as only one factor was extracted.
4. Factor scores were calculated for each participant to represent individual dissatisfaction with overall changes in weight and shape.
The use of factor analysis is limited by small sample size. The Kaiser-Meyer-Olkin (KMO) is a measure of sampling adequacy which should be greater than 0.5 for factor analysis to proceed. In the present analysis the KMO figure came to 0.77 indicating that the sample was adequate for factor analysis. In addition, Bartlett’s Test of Sphericity was checked and found to be non-significant (<0.001) which ruled out the possibility of the correlation matrix being an identity matrix.
Factor scores were calculated for each participant at both 20 and 34 weeks into the pregnancy. The mean factor scores (representing dissatisfaction with overall weight and shape changes) were: at 20 weeks, 0.53 (0.86) for dieters and -0.18 (0.9) for non dieters, and at 34 weeks, 0.55 (0.89) for dieters and -0.20 (0.97) for non-dieters.
Independent t tests were performed on these factor scores to examine whether a significant difference existed between dieters and non-dieters for dissatisfaction with overall weight and shape changes. The results indicated that dieters were more dissatisfied than non-dieters with the overall changes that occurred in their weight and shape at both 20 weeks (t=3.24, 97df, p<0.01) and 34 weeks (t=3.17; 79df; p<0.01).
To identify exactly where differences existed a two (dieters vs non-dieters) by two (ratings of satisfaction: dissatisfied v satisfied / neither) chi-square analysis was performed for each change (weight; stomach; breasts; hips/thighs; face) at both time points in the pregnancy. Tables 11 and 12 present the results of this analysis together with the percentage of dieters and non-dieters that were dissatisfied with the changes in their weight and shape.
T able 11 : D ieters a n d N on-D ieters D issatisfaction w ith th e C hanges in T heir W eight a n d Shape a t Tw enty W eeks.
D issatisfied W ith C hanges In :
D ieters N on-D ieters D ifference
Weight 26.6% 2.5% Z^=15 19;df= l;p< 0.001
Stomach 24.1% 10.1% X^=3.48; d f= l; ns
Breasts 41.3% 20.2% X^=4.92; d f= l; p<0.05
Hips/Thighs 60.7% 20.8% Z^=15.19; df= l;p< 0.001
Face 14.8% 13.3% X^=0.03; df=l;ns
The analysis demonstrated that dieters were more dissatisfied than non-dieters with the changes that occurred in their weight, breasts, and hips/thighs at 20 weeks into the pregnancy. (These differences are illustrated in figures 1 to 3.) However, dieters and non-dieters did not differ significantly in their satisfaction with the changes that took place in their stomach and face.