explicit and implicit attitudes towards food and physical activity in childhood obesity

7/30/2019 Explicit and Implicit Attitudes Towards Food and Physical Activity in Childhood Obesity

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Behaviour Research and Therapy 43 (2005) 11111120

Explicit and implicit attitudes towards food and physical

activity in childhood obesity

Mietje Craeynesta,,1, Geert Crombeza,1, Jan De Houwera, Benedicte Deforcheb,1,Ann Tanghec, Ilse De Bourdeaudhuijb,1

aDepartment of Experimental Clinical and Health Psychology, Ghent University, Henri Dunantlaan 2,B-9000 Ghent, Belgium

bDepartment of Movement and Sports Sciences, Ghent University, Watersportlaan 2, B-9000 Ghent, BelgiumcMPC Zeepreventorium, Koninklijke Baan 5, B-8420 De Haan, Belgium

Received 6 January 2004; received in revised form 16 July 2004; accepted 26 July 2004

Abstract

This study investigated differences in the explicit and implicit attitudes towards food and physical

activities between children with obesity (n 38) and a matched control group (n 38). The implicitattitude was assessed using the Extrinsic Affective Simon Task (EAST; J. Exp. Psychol. (50) (2003) 77), a

modified version of the Implicit Association Test (IAT; J. Personality Social Psychol. (74) (1999) 1464). It

was expected that both groups would report a positive explicit attitude towards healthy food and intense

physical activities, and a negative explicit attitude towards unhealthy food and sedentary activities. Of

particular interest was the hypothesis that children with obesity would have a more positive implicit

attitude towards unhealthy food and sedentary activities than the control group. Results revealed no

differences between groups in the explicit attitude towards food and physical activity. Children and

adolescents with obesity had a more pronounced positive implicit attitude towards food in general. The

relevance of these findings in terms of prevention, treatment and further research is discussed.

r 2004 Elsevier Ltd. All rights reserved.

Keywords: Obesity; Children; Attitude; Implicit; EAST Physical activity; Food

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www.elsevier.com/locate/brat

0005-7967/$ - see front matter r 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.brat.2004.07.007

Corresponding author. Department of Experimental Clinical and Health Psychology, Ghent University, Water-

sportlaan 2, B-9000 Ghent, Belgium. Tel.: +32-9-264-91-38; fax: +32-9-364-64-84.

E-mail address: [email protected] (M. Craeynest).1Member of the Research Institute for Psychology and Health.
http://www.elsevier.com/locate/brthttp://www.elsevier.com/locate/brt


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1. Introduction

Worldwide, childhood obesity is a serious and prevalent problem (Popkin, 1998). It is

acknowledged that obesity is the result of both a genetic predisposition and a behavioural patternof unhealthy eating and physical inactivity. Research has shown that youngsters with obesity

participate less in moderate or vigorous exercise (Trost, Sirard, Dowda, Pfeiffer, & Pate, 2003)

and consume more fat, sugar and proteins than peers without obesity ( McGloin, et al., 2002;

Nicklas, Yang, Baranowski, Zakeri, & Berenson, 2003).

One of the possible explanations for this behavioural pattern may be their attitudes towards

food (Brug, Lechner, & De Vries, 1995) and exercise (Smith & Biddle, 1999): Youngsters with

obesity may have a positive attitude towards unhealthy food and sedentary activities. However,

empirical evidence is at odds with this view. Studies revealed that children with obesity report a

positive attitude towards physical activity (Deforche, Bourdeaudhuij, Tanghe, Hills, & Bode, in

press), and even a less positive one towards unhealthy food than controls (Perl, Mandic,Primorac, Klapec, & Perl, 1998). A simple explanation in terms of attitudes is therefore not

straightforward.

To understand the inconsistency between attitudes and behaviour, it is worthwhile to consider

the view of Fazio (1990), who proposed two different modes by which attitudes can guide

behaviour. According to him, explicit attitudes may guide ones behaviour by a deliberate and

conscious analysis of the costs and the benefits of that behaviour. Alternatively, implicit attitudes

may guide behaviour in a more spontaneous and affective manner, without actively considering

the pros and the cons. Explicit attitudes may be assessed by methods in which deliberation is

possible, such as questionnaires. Implicit attitudes are preferentially measured indirectly by using

reaction time paradigms such as the Implicit Association Test (IAT) (Greenwald, Mc Ghee, &

Schwartz, 1998).Implicit and explicit attitudes towards food in adulthood obesity have been studied by Roefs

and Jansen (2002) using an IAT and questionnaires. Consistent with their hypothesis, no

differences between adults with and without obesity were found for the explicit attitude towards

high-fat food. However, the adults of the obese group did not show a more implicit positive

attitude towards high-fat food: they reported an implicit negative attitude towards high-fat food.

This unexpected finding may be owing to the nature of the IAT, which may have activated societal

instead of personal attitudes towards the categories low-fat and high-fat (see De Houwer, 2001;

Wiers, & de Jong, in press). Indeed, in Western society words such as low-fat and high-fat are

strongly associated with a positive and negative valence respectively. Therefore, it is not

inconceivable that Roefs and Jansen (2002) assessed the societal views towards the labels high-fat and low-fat, rather than the implicit attitudes.

The objective of this study was to investigate the personal explicit and implicit attitudes

towards different kinds of food and physical activities in children with obesity and a lean

control group. Explicit attitudes were assessed by self-reports. Implicit attitudes were measured

by the Extrinsic Affective Simon Task (EAST; De Houwer, 2003), a modified version of the

IAT in which the labels high-fat and low-fat do not have to be used. For the explicit attitude,

we expected that both groups prefer healthy food, and moderate and high intense physical

activities in comparison with unhealthy food and sedentary activities. For the implicit attitude,

we expected that, in comparison with the control group, participants with obesity prefer

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unhealthy food to healthy food, and prefer sedentary activities to moderate and high intense

physical activities.

2. Method

2.1. Participants

Thirty-eight children and adolescents with severe obesity (mean ABMI2=166.09%, SD=31.18;

17 boys; age: M=13.69, SD=2.63, range 918 years old) were recruited during the first week of

an inpatient treatment in a Belgian medical-paediatric centre, which is specialized in the treatment

of youth obesity. Thirty-eight youngsters without obesity were recruited in schools, and were

matched by gender, age and educational level (mean ABMI=107.34%, SD=18.85; 17 boys; age:

M=13.53; SD=2.52, range: 918 years old).

2.2. Materials and procedure

EAST paradigm: The EAST (De Houwer, 2003) consists of two practice blocks and a

subsequent test block. In the first practice block, white words are presented. Participants press a

left or a right key in response to the valence of the words (I like to do or to eat/I do not like to do

or to eat). That way, participants learn an extrinsic association between a positive (negative)

valence, and the left (right) key. In the second practice block, participants press the left or the right

key in response to the colour of words. In the experimental block, a combination of white and

coloured words is presented. Participants categorise the white words in response to their valence,and the coloured words in response to their colour. Of importance is the performance on the

coloured words. It has been shown that the valence of the coloured words affects the colour

categorisation: task performance is better when the response for the colour is compatible with the

response for the valence of the word (congruent trials; e.g., press right for happy because it is

written in green when the right response is also correct for positive white words), and the

performance is less when the response for the colour is incompatible with the response for the

valence of the word (incongruent trials; e.g., press left for happy because it is written in blue when

the left response is also correct for negative white words).

Participants carried out two EASTs: One task was related to physical activity, and one was

related to food. Each task lasted about 15 min. The order of the tasks was counterbalanced. The

tasks were run on an IBM compatible Pentium II laptop with a 15 00 colour screen using Inquisit1.31 software, which measures RTs to keyboard presses with millisecond accuracy (De Clercq,

Crombez, Roeyers, & Buysse, 2003).

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2The Body Mass Index (BMI; weight/height2; kg/m2) is accepted as a reliable and valid index of relative adiposity.

However, since mean normal values of BMI vary substantially with age and values for individuals of different ages are

difficult to compare, an adjusted BMI (ABMI) was used. ABMI was calculated using the formula (actual BMI/ideal

BMI [50th percentile for same sex and age]) 100 (Valverde, Patin, Oliveira, Lopez, & Vitolo, 1998). The 50th

percentiles were derived from Flemish growth reference charts.

M. Craeynest et al. / Behaviour Research and Therapy 43 (2005) 11111120 1113


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EAST words: Before each task, the participant provided words for physical activities or foods

that he/she really (dis)liked. All words were possible, except the ones for the coloured trials. These

individually selected words were used for the white EAST trials. There were nine preselected

words related to physical activity, divided into three categories: sedentary activities (reading,resting and watching television), moderate intense activities (walking, cycling and

swimming) and high intense activities (running, training and exercising). There were also

six preselected words related to food, divided into two categories: unhealthy food (French fries,

crisps and coke) and healthy food (tomato, apple and water). Preselected words were

chosen by the experimenters based upon results of earlier studies (Deforche et al., in press). These

words were used for the coloured EAST trials.

EAST trial and blocks: Each trial began with a white fixation cross for 315 ms; next, a (white/

blue/green) word was presented until a correct response was given. In case of an incorrect

response, a red cross appeared for 400 ms at the place of the word. The default Inquisit values

were used for white. Blue was created by setting the red, green and blue values of Inquisit at 0,125, and 150, respectively. Green was created by setting the red, green and blue values of Inquisit

at 0, 150, and 125, respectively. All words were presented on a black background. A letter was

7 mm high and 5 mm wide. The inter-trial interval was 1200 ms. During the first practice block, the

individually selected words appeared randomly four times in a white colour on the screen.

Participants were instructed to classify the 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 the second practice block, each of the coloured words was presented 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. The physical activity task contained four test blocks of 32 trials (14 white trials, 18coloured 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).

Self-report: After the EAST tasks, participants rated the valence of the preselected food and

physical activities words using a 7-point scale (3: dislike; +3: like).

3. Results

3.1. EAST tasks

The responses on the coloured test trials were analysed (De Houwer, 2003). Trials with an

incorrect response were discarded. In line with Greenwald et al. (1998), reaction times (RTs)

below 300 ms or above 3000 ms were recoded to 300 and 3000 ms, respectively. All RTs were log-

transformed. Delta (d) is reported as an estimate of effect size. A d of .01, .10 and .25 was used as a

threshold to define small, medium and large effects, respectively (Cohen, 1988).

Physical activity: All relevant means can be found in Table 1. A 2 (group: youngsters with

obesity vs. youngsters without obesity) 3 (word category: sedentary, moderate intense, vs. high

intense physical activities) 2 (extrinsic response valence: positive vs. negative)-ANOVA was

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performed on the mean log-transformed RTs. There were no significant effects, Fo2:09; except a

borderline significant main effect of extrinsic response valence, F1; 74 3:63; p :06; d :05:

participants tended to be faster to give a response that was associated with a positive valence (e.g.,

the right key; M=830 ms, SD=234 ms) than to give a response that was associated with a

negative valence (e.g., the left key; M=841 ms, SD=231 ms). The percentage of errors was

analysed using the same 2 3 2 ANOVA. No effects were significant, Fo2:15:

Food: The reaction times (see Table 1) were analysed using a 2 (group: youngsters with obesity

vs. youngsters without obesity) 2 (word category: healthy vs. unhealthy food) 2 (extrinsicresponse valence: positive vs. negative)-ANOVA. Again there was a significant main effect of

extrinsic response valence, F1; 73 7:86; po:01; d :10: participants were faster to give a

response that was associated with a positive valence (M=800 ms, SD=202 ms) than to give a

response that was associated with a negative valence (M=828 ms, SD=207 ms). The analysis also

revealed a borderline significant interaction effect between group and extrinsic response valence,

F1; 73 3:68; p :06; d :05: For the youngsters with obesity, there was a significant

difference in RT between the trials with a positive (M=795 ms, SD=226 ms) and trials with a

negative (M=846 ms, SD=252 ms) extrinsic response valence, t36 3:19; po:01; d :22: For

the control group, this effect was not significant, to1 (M=806 ms, SD=178 ms; M=810 ms,

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Table 1

Mean and standardized reaction times (RT) and percentage of errors of the obesity and normal-weight group on

physical activity and food trials as a function of word category and extrinsic response valence

RT (ms) % of errors

Obesity Normal-weight Obesity Normal-weight

M SD M SD M SD M SD

Physical activity

Sedentary

Pos 836 250 826 247 8.33 9.49 10.24 12.27

Neg 852 242 850 210 7.80 7.43 10.88 14.93

Moderate intense

Pos 866 285 804 177 7.02 9.59 9.61 12.00

Neg 880 289 817 238 8.55 9.39 10.95 16.46

High intense

Pos 824 222 824 221 7.67 9.17 9.40 10.26

Neg 844 209 805 195 6.14 9.02 12.03 17.07

Food

Unhealthy food

Pos 796 237 803 179 7.87 7.90 8.98 6.88

Neg 839 251 813 165 6.87 7.55 9.53 11.04

Healthy food

Pos 794 215 808 177 6.75 7.56 8.66 9.94

Neg 853 252 806 160 8.47 6.55 11.98 10.44



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SD=163 ms, respectively). This pattern indicates that youngsters with obesity have a positiveimplicit attitude towards the presented food items, whereas the normal-weight youngsters were

rather neutral towards them (see Fig. 1).

The same 2 2 2 ANOVA was performed upon the percentage of errors. Only the interaction

effect of word category and extrinsic response valence was marginally significant, F1; 73 3:29;

p :07; d :04: For the healthy food words, there was a significant difference in the percentage of

errors between trials with a positive (M=7.71%, SD=8.75%) and trials with a negative

(M=10.23%, SD=8.50%) extrinsic response valence, t74 2:07; po:05; d :06: For the

unhealthy food words, this effect was not significant, to1 (respectively M=8.43%, SD=7.39%;

M=8.20%, SD=9.30%). This pattern of results indicates that both groups have a positive

attitude towards healthy food, and a neutral attitude towards unhealthy food.

3.2. Self-report

The explicit attitudes towards physical activity and food were obtained by averaging the item

scores for each category of physical activity and for each category of food (see Table 2).

Physical activity: A 2 (group: youngsters with obesity vs. youngsters without obesity) 3 (word

category: sedentary vs. moderate intense vs. high intense physical activities)-ANOVA was used.

The main effect of group was not significant, F1; 74 1:19; but the main effect of word category

was, F1; 73 5:43; po:01; d :29: both groups were more positive towards moderate intense

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500

600

700

800

900

1000

1100

obesity normal-weight

group

RTinms

positive response

valence

negative responsevalence

Fig. 1. Mean reaction times on food trials with positive and negative responses in children with and without obesity.



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physical activities (M=1.78, SD=1.05) than towards sedentary ones (M=1.48, SD=.94), t75

2:14; po:05; d :06: They were also more positive towards moderately intense physical activities

than towards high intense ones (M=1.20, SD=1.10). The interaction effect of group and word

category was not significant, F1; 73 1:31; nor were any of the other effects, all Fo1:

Additional t-tests showed that all word categories were positively evaluated (i.e., received a mean

rating above zero), t49:58; po:001:

Food: A 2 (group: youngsters with obesity vs. youngsters without obesity) 2 (word category:

unhealthy vs. healthy food)-ANOVA was carried out. No effects were significant, all Fo1:56; and

both categories were positively evaluated (M=1.72, SD=.77), t411:08; po:001:

4. Discussion

This study investigated whether explicit and implicit attitudes towards food and physical

activity differed between children and adolescents with and without obesity. For the explicit

attitude, it was expected that both groups prefer healthy food, and moderate and high intense

physical activities to unhealthy food and sedentary activities. For the implicit attitude, it was

hypothesized that youngsters with obesity prefer unhealthy food and sedentary activities to

healthy food and physical activity.For the explicit attitudes, results are mainly in line with our ideas. Both groups did not differ in

their explicit attitudes towards food and physical activity. There was however no differential

liking for healthy behaviour in comparison with unhealthy behaviour. Both groups reported a

similar positive attitude towards sedentary, moderate and high intense physical activities, and

towards healthy and unhealthy food. There are at least two explanations for the latter finding.

First, it is possible that other attributes (such as the taste of food and the fun of activities) are

more salient than health. Second, it is possible that healthy and unhealthy behaviours may not be

conceived of as two opposite sides of a coin (Marshall, Biddle, Sallis, McKenzie, & Conway,

2002): People may like watching TV and reading (sedentary activities), and at the same time they

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Table 2

Mean and standardized explicit attitude of the obesity and normal-weight group towards different kinds of physical

activity and food, evaluated on a scale from 3 to +3

Obesity Normal-weight

M SD M SD

Physical activity

Sedentary 1.59 1.03 1.37 .85

Moderate intense 1.99 1.04 1.57 1.06

High intense 1.12 1.07 1.28 1.13

Food

Unhealthy 1.46 1.57 1.86 .95

Healthy 1.83 .98 1.74 1.05



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may enjoy swimming (moderate intense physical activities) and even running (high intense

physical activities). The same probably holds for healthy and unhealthy food: Those who like

healthy food may also like less healthy food such as crisps and coke.

The results for the implicit attitudes were not as expected. Youngsters with obesity did nothave a more positive implicit attitude towards sedentary activities. They also did not have a more

pronounced negative implicit attitude towards physical activities. The same was true for food:

youngsters with obesity did not prefer unhealthy food to healthy food. One potentially interesting

result was revealed. Youngsters with obesity had a more positive implicit attitude towards

both healthy and unhealthy food. This effect was not present in youngsters without obesity.

This pattern of results may indicate that children with obesity not really prefer unhealthy food,

but simply like eating. Assuming that attitudes are important precursors of behaviour, it seems

that obesity is not specifically related to eating unhealthy food, but rather to eating a lot. In

support of this view, Jansen et al. (2003) found that children with overweight ate more than

their normal-weight peers when exposed to food cues. Also in line with this idea, is that inadults with obesity a diet with calorie restriction was more effective in maintaining weight loss

than a diet with fat restriction (Harvey-Berino, 1999). The idea that youngsters with obesity

like food in general awaits further corroboration. The EAST may be easily adapted to inves-

tigate this idea: the attitude towards food stimuli may be compared with the attitude towards

alternative stimuli.

There are a number of methodological and theoretical issues that arise from this research. First,

there are few studies that have investigated implicit attitudes in obesity ( Roefs & Jansen, 2002),

and this study was the first to use the EAST paradigm. There is a need for replication and

extension. Second, a largely unexplored issue in the attitude literature concerns the assumption

that an implicit attitude measures the real attitude underlying behaviour. Although intuitive

appealing, there is still limited evidence for the idea that persons who behave unhealthy have apositive implicit attitude towards that behaviour. Often those who behave unhealthy have also a

negative implicit attitude (Swanson, Rudman, & Greenwald, 2001; Wiers, van Woerden,

Smulders, & de Jong, 2002). Third, it is still unknown whether an implicit attitude should be

conceived of as stable and context independent. It is possible that attitudes are multidimensional

and consist of various attributes that mutually interact. Whether and which attribute is activated

and becomes salient, may largely depend upon the context and upon the affective or motivational

status of the individual (Blair, 2002; Gheldof, de Jong, Vinck, & Houben, 2004). Future research

may benefit by varying exposure to food cues (e.g. food odours), and by varying the level of

hunger. Fourth, it is yet unclear why there were no results at all for the implicit attitude towards

physical activities. A reason may be that the attitude towards physical activities is much morecontext dependent (social context, weather, etc.) than the attitude towards food. Fifth, it is

possible that the behavioural pattern of eating too much in obesity is less related to liking

(valence) than to wanting (arousal) (see Berridge, 1996). This is the core idea of the incentive-

sensitisation theory of addictive behaviours (Robinson & Berridge, 1993). Implicit assessments of

wanting alcohol have been showed to differentiate better between heavy and light drinkers than

implicit measures of liking alcohol (Wiers et al., 2002). This result has been replicated and

extended in alcohol addicted patients (Houwer, Crombez, Koster, & Beul, in press). To explore

this hypothesis the implicit measures may be adapted to investigate the associations between food

stimuli and arousal attributes.

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