Research ReportEffect of television advertisements for foods on food consumption in children
Introduction
A substantial body of research indicates that the prevalence of obesity in childhood is increasing. The classic externality theory of obesity postulates that the obese are more influenced by external stimuli than are the lean (Schacter, 1971). Direct exposure to certain types of food, such as processed and snack foods high in fat and sugars, generally energy dense, may contribute to the development of child obesity. A critical indirect influence on children's food choices and intake may be advertising of foods on television. Many correlational studies have demonstrated an association between the duration of TV viewing and levels of overweight and obesity in both children and adolescents (Anderson, Crespo, Bartlett, Cheskin, & Pratt, 1998). However, such cross-sectional studies fail to demonstrate a causal link from viewing TV ads to extra eating. Kaur, Choi, Mayo, and Harris (2003) conducted a prospective study in which it was found at the three-year follow up that those who watched two or more hours of TV per day were twice as likely to become overweight during the course of the study. Two other longitudinal studies have produced similar findings (Francis et al., 2003, Proctor et al., 2003). This supports the notion that excessive TV viewing does contribute to weight gain. Furthermore, in a 6-months intervention study in which children's television viewing was substantially limited, Robinson (1999) found that rises in BMI and fat deposition were significantly less than in a control group without intervention. These data also support the hypothesis that exposure to current television programming helps to cause weight gain in children.
The effect of TV viewing on weight gain seems to be, at least in part, due to a lack of physical activity rather then the act of viewing itself (Hu, Li, Colditz, Willett, & Manson, 2003). However, TV may not just promote sedentary behaviour. There is evidence that it also stimulates food intake. TV viewing is associated with overconsumption in girls, specifically of snack foods (Francis et al., 2003). Children who eat their meals in front of the TV tend to consume more dietary fat (Coon, Goldberg, & Rogers, 2001). Woodward et al. (1997) found that the number of hours of TV viewing by teenagers was significantly correlated with the number of unhealthy food items consumed per day.
There is another way in which TV viewing may induce food consumption. Furnham, Abramsky, and Gunter (1997) noted that, during programmes scheduled for children over two consecutive weekends, 37% of the adverts on TV channels in the USA and 49% on the UK TV channels were for food. The majority of advertised products were snack foods, followed by breakfast cereals and then fast food outlets. Also Lewis and Hill (1998) found that half of the advertisements on British television were for food items.
Previous studies have shown that exposing children to different types of food adverts may influence their subsequent food choices but there is little evidence to show a direct causal relationship. Therefore, a study was devised in order to assess if children attended to and recognised food advertisements on television more often than advertisements not for foods. In the light of Schachter's externality theory, we were interested in ascertaining if overweight or obese children are more responsive to food adverts. So we sought to determine if there was any difference between normal weight and overweight/obese children in the ability to recognise food adverts, as well as assessing the impact of recent exposure to TV food adverts on total intake of food and choice among foods. It was hypothesised that (i) obese and overweight children would recognise more food-related adverts than their normal weight counterparts, (ii) an increased ability to recognise food-related ads would be associated with the amount of food consumed after food advert exposure, and (iii) the child's weight status (weight in the healthy range, overweight or obese) would also influence the types and the total amount of food consumed during the test sessions.
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Participants
A total of 42 school children (18 male, 24 female) aged 9–11 years (mean age 10.4 years) from a Liverpool primary school participated in the study. Three groups were created; lean, overweight and obese, based on body mass index (BMI) converted to a standard deviation score using the revised 1990 reference standards (Cole & Preece, 1990). A majority (28) of the children were lean (BMI≤25 kg/m2), nine were overweight (25<BMI<30 kg/m2) and five were obese (BMI>30 kg/m2). The proportions of
Recognition of advertisements
As predicted, the obese and overweight children recognised significantly more food ads (means of 7.6 and 7.4, respectively, Fig. 1) than did the lean children (whose average was 6.25 out of eight), χ2(2)=19.2, p<0.001. The lean, overweight and obese groups on average each recognised similar numbers non-food ads (a grand mean of 6.0).
Food intake
The obese and overweight groups ate significantly more than the healthy-weight group (Fig. 1), both with food ads (FA), χ2(2)=24.3, p<0.001, and with non-food ads
Discussion
Despite the small sample, the findings of our study reliably support the hypotheses. Obese children did recognise a greater number of food than non-food advertisements from TV. A similar effect was seen in the overweight children, whereas in the children with a BMI in the healthy range this difference between conditions did not appear.
This effect is not attributable to obese or overweight children recognising more ads in general or falsely identifying more ads as presented in the test, because
Acknowledgements
We thank Melany Ball, Gillian Cooper and Dr Andrew Goudie of the Kissileff Laboratory for their help. The Biotechnology and Biological Sciences Research Council supported Terry Dovey. The Laboratory's website URL is http://www.liv.ac.uk/Psychology/kissilefflab/Home.html
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