DIRECCIÓN POSTAL DE LAS DIRECCIÓN DE ASISTENCIA AL PERSONAL

Having confirmed some of the outcomes of Experiment 1, that women scoring high on the TFEQ-D scale also show greater general impulsivity, an important question is to what extent do individual differences in impulsivity predict intake in the snack test.? To address this, a step wise, exploratory multiple regression was used to explore the relationship between calorie consumption, self-report overeating, and the

0 100 200 300 400 500 600

HDHR HDLR LDHR LDLR

different measures of impulsivity. Table 3.5.3.a shows regression coefficients of the final model, and Table 3.5.3.b shows the excluded variables in the model.

The final model indicated that TFEQ-D was the only significant predictor of actual caloric intake, using a multiple regression stepwise method. This confirmed the outcome of the earlier ANOVA analysis. However, the impulsivity measures failed to predict eating even though they differed between TFEQD groups. Final results show that TFEQ-D accounted for 32% of the variability of the model.

Table 3.4.3.b: Excluded Variables in the Regression Model to account for Caloric Consumption based on Individual Differences

As Table 3.5.3.b illustrates, all other variables entered into the Food Consumption model were excluded, as all t-values were insignificant and therefore do not represent significant predictors. This result was surprising in light of the significant literature that supports the link between the two TFEQ scales (D and R), which is discussed in greater detail in the General Discussion.

3.5 Discussion

The overall outcome of Experiment 2 confirmed that high scores on the TFEQ-D were associated with greater inhibition impulsivity as indicated on the MFFT

Table 3.4.3.a:Regression Co-Efficients of Overeating Behavior

B SE B Beta

Step 1

Constant 231.6 62.62

TFEQ-D 18.95 7.82 0.32**

Note: R²for step 1= 0.32, ** p<0.01

B t Sig

TFEQ-R 0.054 0.413 0.681, ns

DDT AUC 0.116 0.909 0.368

DDT k-value 0.006 0.042 0.876, ns

BART Explosions 0.116 0.909 0.368, ns

BART Adjusted

Average Pumps 0.024 0.192 0.849

MFFT Time -0.131 -0.997 0.323, ns

MFFT Errors -0.098 -0.762 0.449, ns

MFFT i-score 0.021 0.162 0.87

measure. Our results also verified that actual overeating is indeed predicted by self-reported overeating measures (TFEQ-D scores) in lean healthy females. Contrary to our hypothesis, intake in the snack test was not predicted by the interaction between TFEQ-D and TFEQ-R scores, nor was it predicted by impulsivity performance, suggesting that the relationship between impulsivity with regard to overeating behavior is complex.

An important aim of this study was to compare a performance-based measure of inhibition (MFFT) alongside two other measures of reward reactivity (BART and DDT). Several different outcomes were possible here. Firstly, that a tendency to overeat (i.e. high scores on TFEQ-D) represent a heightened response to rewards, perhaps as indicated by the tendency for women scoring high on this measure to show greater sensitivity to palatability (M. R. Yeomans, Tovey, et al., 2004) and to more rapidly acquire liking through associations between flavours and hedonic rewards (M.

R. Yeomans, Tovey, et al., 2004). If so, the prediction would have been that both the DDT and BART measures would show greater impulsivity for those scoring high on the TFEQ-D, but this would not be predicted for the MFFT. Again, the literature lends support to the reward sensitivity part of this hypothesis: scores on TFEQ-D correlate with performance on the DDT (Experiment 1 and Yeomans et al(2008)), and BART scores correlated with TFEQ-D scores (Experiment 1). However, although there was a trend for higher responses on the DDT, this was not significant in Experiment 2, and the BART findings from Experiment 1 did not replicate.

Moreover, high scorers on the TFEQ-D were significantly more impulsive on the MFFT. Thus the pattern of data do not fit well with a simple model that suggests TFEQ-D equates with increased Reward Reactivity. A second possibility, and once again which could be supported by the literature (C. Nederkoorn, Van Eijs, Y.,

Jansen, A., 2004a), is that a lack of inhibitory control (i.e. higher scores on the MFFT) would be seen in women who are poor at maintaining restraint, i.e. those that scored high on both TFEQ-D and TFEQ-R, and potentially those women who score high TFEQ-D, but not on TFEQ-R.

One of the most interesting findings to emerge from this investigation is that there were significant differences in performance on the MFFT between the TFEQ groups.

Aspects of each groups‟ MFFT scores fit within our original prediction that high

TFEQ-D scores would be associated with greater impulsivity, and low TFEQ-D would be associated with lesser impulsivity; certainly the LDLR group fits this profile, as their performance on this task was the least impulsive of any subcategory.

The distinction between the other three groups is more complicated; the difference between the HDHR and HDLR group approached significance, with the HDHR performing less impulsively than the HDLR. This raises a question with regard to the beneficial properties of self reported Restraint, which is that it could have protective benefits for those individuals with high TFEQ-D classification. The high TFEQ-R score may relate directly to MFFT reflectivity, as it may express an individual‟s increased attention devoted to selecting specific stimuli, i.e. the selection of correct items on the MFFT.

One could also speculate that differences in the TFEQ-D subcategories are related to the concept of a “controlled” eating environment, and these had subsequent influences both in terms of impulsivity performance and eating behavior. Based on obesity related research that highlights obese and overweight individuals‟ tendency to skip breakfast, one might be able to argue the same case for those in the high TFEQ-D group, and the control breakfast may have actually served to enhance the high TFEQ-D group‟s performance on the impulsivity tasks. The variable of breakfast

consumption had not been considered in the design of this study, as our primary aim was to control caloric intake, but nonetheless may have significant bearings on the results of the current investigation.