PASO 4: SELECCIÓN DE INDICADORES DE MONITOREO

7.5.1 Analyses

Five health behaviours: low dietary fat intake, high dietary fibre intake, healthy eating habits, five or more servings o f fruit and vegetables a day and high physical activity were examined, with three measures o f disordered eating: anorexic symptoms, bulimic symptoms and emotional eating. The association between healthy and unhealthy weight control and these behaviours were examined using logistic regression. This allows examination of the relative odds of an individual falling into a high scoring group for a behavioural outcome, based on their weight control style whilst controlling for the effects of BMI and puberty.

7.5.2 Weight Control Style and Health Behaviours (Healthy Eating and Physical Activity)

The unadjusted percentage of individuals in each weight control style group scoring highly for each of the health behaviours is shown in table 7.14. Separate logistic regressions were carried out for each of health behaviours. In each case weight control style was entered as a categorical independent variable and BMI and puberty additional independent variables. As before a score of 1 indicated the healthy form of the behaviour, a score o f 0 indicated the unhealthy form. Table 7.15 shows the relative odds o f an individual from each weight control style group falling into the healthy category for each health behaviour.

Chapter 7. Cross-sectional analyses: healthy and unhealthy dieting behaviours

Table 7.14 Number (%) of members of each weight control style group scoring highly for each health behaviour.

N High Dietary fibre Low Dietary fat Healthy dietary habits Five fruit and veg Physical activity No Weight control 390 193 (49.5) 247 (36.2) 114(29.3) 133 (34.3) 210(53.8) Healthy weight control 264 136(51.5) 118(55.1) 135 (51.1) 111 (42.0) 157(59.5) Unhealthy control 511 290 (56.7) 219(57.1) 249 (48.8) 217(42.5) 283 (55.4)

Table 7.15 Logistic Regressions: Odds of healthy behaviours by dieting group

Variable Weight control group Wald x' Odds

ratio

95% Cl

Dietary fibre No Weight control 1

Wald x^[2]=4.80 ns Healthy weight control 0.27 ns 0.91 0.66-1.27 Unhealthy control 4.34 ns 0.54 0.54-0.98

Dietary fat No Weight control 1

Wald x^[2]=20.8 p<0.001 Healthy weight control 12.6*** 1.84 1.32-2.59 Unhealthy control 18.6*** 1.94 1.44-2.63

Healthy Eating Habits No Weight control 1

Wald x^[2]=25.2 p<0.001 Healthy weight control 20.94*** 2.23 1.58-3.14 Unhealthy control 18.29*** 1.97 1.44-2.68 Five fruit and vegetables No Weight control 1

Wald

x\2]=

Physical activity No Weight control 1

Wald x^[2]=1.84 ns Healthy weight control 1.35 ns 1.22 0.87-1.71 Unhealthy control 1.46 ns 1.20 0.89-1.62 Index category = No weight control "p<0.05 **p<0.01 ■'p<0.001

Significant differences between weight control groups were found for all the health behaviours except dietary fibre (Wald ^ =4.80 [df=2] ns) and physical activity (Wald ^ =1.84 [df=2] ns). Both healthy and unhealthy weight controllers were more likely to eat a low fat diet than non weight controllers (Wald x^'=20.8[df=2] p<0.001), although confidence intervals suggested that the

Chapter 7. Cross-sectional analyses: healthy and unhealthy dieting behaviours

healthy weight controllers did not differ significantly from the unhealthy weight controllers. Healthy eating habits were higher amongst the weight controllers (Wald =25.2 [df=2] p<0.001), but did not vary significantly between healthy and unhealthy weight controllers. The greatest likelihood o f eating more than five fruit and vegetables a day (Wald =7.9 [df=2] p<0.0))was found amongst the unhealthy dieters, whilst the difference between the non weight controllers and the healthy weight controllers was at the margins o f significance (p=0.052).

7.5.3 Associations Between Weight Control Style and Disordered Eating

Logistic regression was used to examine the association between healthy and unhealthy weight control style and disordered eating. The unadjusted percentage of individuals in each weight control group showing signs of each type of disordered eating is shown in table 7.16. Separate logistic regressions were carried out for each of the three disordered eating variables. In each case BMI and puberty were entered as covariates. Table 7.17 shows the relative odds of an individual from each weight control style group falling into the eating disordered category for anorexic symptoms, bulimic binge eating and emotional eating.

N

i

signs of disordered eating

Table 7.16^ercentage)of members of each weight control style group showing

N Anorexic symptoms (ChEat) Bulimic symptoms (EDI-Bu) Emotional eating (DEBQ-Em) No Weight control 385 14(4) 45 (12) 69(18)

Healthy weight control 264 19(7) 25 (10) 55 (21)

Chapter 7. Cross-sectional analyses: healthy and unhealthy dieting behaviours

Table l A l Logistic Regression: Odds of disordered eating behaviours by weight control group

Weight control group Wald x^ Odds ratio 95% Cl

Anorexic symptoms No Weight control 1

Wald [2]=124.9*** Healthy weight control 3.0 ns 2.0 0.92-4.19 Unhealthy weight control 76.0 *** 15.8 8.49-29.4

Bulimic symptoms No Weight control 1

Wald

y^

Emotional eating No Weight control 1

Wald [2]=8.4* Healthy weight control 0.17 ns 1.09 0.72-1.66 Unhealthy weight control 6.73** 1.60 1.12-2.29 Index category = N o dieting *p<0.05 **p<0.01 ***p<0.001

Significant differences between groups emerged for all three disordered eating variables: Anorexic symptoms (Wald =124.9 [df=3] p<0.001), bulimic binge eating (Wald %^=50.9 [df=3] p<0.001) and emotional eating (Wald y} =8.43 [df=3] p<0.05). In each case the unhealthy weight controllers differed significantly from the non weight controllers and showed an elevated likelihood of being in the eating disordered group. For none of the three variables did healthy weight control prove to be associated with elevated likelihood o f being in the disordered eating groups. In the case o f anorexic symptoms and bulimic binge eating, but not emotional eating, confidence intervals suggested that the healthy weight controllers were significantly less likely to show symptoms than unhealthy weight controllers.

7.6 Are Differences in Levels of Disordered Eating Between Healthy and