TV, using computers and playing videogames, is predicted to be more strongly associated with child obesity than a lack of physical activity (Lazarou & Soteriades, 2010; Maher, Olds, Eisenmann, & Dollman, 2012), despite the fact that sedentary lifestyles lead to a lack of physical activity (Berentzen et al., 2014; Brown, Nicholson, Broom & Bittman, 2011; Jackson, Djafarian, Stewart & Speakman, 2009; WHO, 2015a).
A recent systematic review of longitudinal studies provides evidence indicating that there is a yearly increase in the mean weight for girls (5.8%) and boys (5.7%) as a result of a daily sedentary lifestyle. Also, the sedentary behaviour of children and adolescents
increases with age by nearly 30 minutes extra per day ever year (Tanaka, Reilly, & Huang, 2014).
Many research studies on sedentary behaviour show that screen time alone is linked to overweight and obesity in children and adolescents (Falbe et al., 2013; Maher, Olds, Eisenmann, & Dollman, 2012; Morales-Ruán et al., 2009; Stamatakis et al., 2013; Steele et al., 2009). For instance, a systematic review of cross-sectional studies aimed to examine the level of overweight and obesity in relation to physical activity and
sedentary behaviour among children and adolescents. Overall, the findings indicate that the time spent on sedentary behaviour was significantly associated with BMI, while physical activities were not associated in some studies (Prentice-Dunn & Prentice- Dunn, 2012).
A longitudinal study of prospective observational design was conducted in the US by Mitchell, Pate, Beets and Nader (2013) to determine whether the time spent in sedentary activity is associated with the BMI among participants aged 9–15 years (N = 789). The results show that BMI of children and adolescents was significantly associated with the sedentary behaviour independent of moderate to vigorous physical activity. In addition, a study of Canadian children aged 8–10 years assessed children’s behaviour in relation to physical inactivity; the study found that nearly 46% of girls and 19% of boys met the recommendations of the Canadian sedentary behaviour guidelines for children who have screen time of 2 hours per day. Those who engaged in sedentary behaviour were significantly higher in overweight and obesity compared to children of normal weight (Herman et al., 2014).
Overweight and obesity is not only associated with sedentary behaviour in terms of inactivity, it is also associated with the unhealthy dietary habits of those engaged in sedentary activities (Cox et al., 2012; Manios et al., 2009; Pearson & Biddle, 2011; Rey-López et al., 2011). For instance, a cross-sectional study conducted among USA children and adolescents (N = 12,642) identified that TV watching was negatively associated with fruit and vegetable intake and significantly related to the intake of fast food, candy and skipping breakfast (Lipsky & Iannotti, 2012). A longitudinal study was conducted by Falbe et al. (2014) with US children and adolescents (N = 8272). The authors used consecutive questionnaires for 2 years to assess dietary changes over time. The results indicated that for each hour increase in screen time there was a decreased intake of fruit and vegetables and an increase in the consumption of SSBs, sweets, salty snacks and fast food (Falbe et al., 2014).
A study was conducted in Canada to determine the relationship between the time spent in sedentary activities and the frequency of food consumption among Canadian children aged 9–11 years (N = 523) (Borghese et al., 2014). The evidence showed that TV watching was negatively associated with healthy food and positively associated with consumption of unhealthy foods, such as sweets, ice cream, potato chips and fast food (Borghese et al., 2014). Further, the results from Borghese et al. (2014) indicated that unhealthy eating habits were strongly associated with body weight than is the total time spent on sedentary behaviour. Similarly, Pearson et al. (2014) found that TV viewing during the school day and on weekends was significantly associated with unhealthy dietary habits among Australian adolescents.
In the same context, television advertisements are one of the most harmful elements of TV watching. A longitudinal study by Andreyeva, Kelly and Harris (2011) was conducted to identify the effect of TV advertising on children’s food intake and body weight between the years 2002 and 2004. They found a positive correlation between food advertising and an increased intake of fast food and soft drinks, which was associated with a 9.4% rise in children’s intake of SSBs and a 1.1% rise in fast food consumption in 2004 (Andreyeva, Kelly, & Harris, 2011). In addition, exposure to food advertisements on TV was associated with the desire to eat (Kemps, Tiggemann, & Hollitt, 2014) and was significantly associated with attraction to purchasing the products (Costa, Horta, & Santos, 2012). Moreover, every one point rise in TV fast food adverting increased the risk of obesity by 19% (McClure et al., 2013), while a reduction in food advertising to zero reduced the average of BMI by 0.38 kg/m2 and lowered the
rate of obesity from 15.9% to 13.5% among girls and from 17.8% to 15.9% among boys (Veerman et al., 2009).
In summary, it appears from the literature review that sedentary activities are among the main risk factors contributing to obesity in children, not only as a result of the time spent on sedentary activities, but also due to the other behaviours acquired from the TV programs and advertisement. Boulos et al. (2012) point out that there are three possible explanations for the direct relationship between body weight and TV viewing. First, TV watching is a sedentary activity that decreases one’s amount of physical activity.
Second, unhealthy food advertisements stimulate the intake of non-nutritious food. Third, watching TV is linked with mindless dietary intake.