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Considering the evidence provided in section 2.4 that during mid-to-late childhood, PA appears to decrease and overweight and obesity increase without a rise in television viewing, it is pertinent to discuss the potential effects of sedentary screen based media. In terms of weight status, a randomised controlled study provided initial evidence that time spent using screen based media affected child weight status (Epstein, Paluch, Gordy, & Dorn, 2000). Ninety obese 8-12 y old children were randomly assigned to one of four treatments, two treatments aimed to reduce television viewing and computer game play and another two to increase PA every day over either 10 or 20 weeks. The dose-response relationship was examined to establish whether weight reduction and increased fitness were attributable to reduced screen time or increased PA. Both were found to be effective, as they produced equal levels of weight loss and increased fitness in the children (Epstein et al., 2000). Screen time and PA however were measured by self-report and so

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whether the children’s PA had in fact, improved was not evidenced as it was not corroborated by an objective measure, such as accelerometry. Furthermore, dietary intake was not measured and parents were aware that their children were participating in a weight-related study. As such there may also have been a change in the children’s EI and so there is no tangible evidence that the weight loss was wholly due to the increase in PA or decrease in sedentary time.

Further evidence of a relationship between weight status and screen time was provided when both were measured in US children aged from 1-12 y (n=2831) (Vandewater, Shim, & Caplovitz, 2004).

In the whole sample no association was found between television viewing and weight status.

However in the children aged 9-12 y old, those with lower weight status typically used the computer for non-gaming purposes for moderate amounts of time. Those with higher weight status used it for non-gaming purposes either very little, or a lot. As this was only relevant to those aged 9-12 y, it was suggested that at this older age it was more likely that they used the computer for homework and email. The screen time data however was collected using 24 h time use diaries which were completed by a parent or carer (Vandewater et al., 2004). The reporting by some parents might also have been subject to social desirability bias, particularly those with children of high weight status (Aresu et al., 2009; Basterfield et al., 2008).

The Raine study (Hands et al., 2011) discussed previously in section 2.4, also investigated associations between screen time and weight status in boys and results were more consistent than those of Vandewater and colleagues (2004), possibly due to it being longitudinal. High screen use (watching television and computer game play for >120 min per day) increased from 22.2% at 8 y to 52.8% at 14 y. Along with this rise in prevalence of high screen use, overweight and obesity also increased from 15.8% at 8 y to 24.1% at age 14 y. However, as already mentioned (section 2.4.1), the data was collected by proxy parent report at 8 y and 10 y and then self-reported at 14 y.

In a more recent study that investigated the computer use and television viewing of 4072 children aged 4-13 y, the collection of dietary data was included (De Jong et al., 2013). Computer use was not found to be associated with being overweight. Yet in contrast to previous work, there was a relationship with television viewing for >1.5 h per day, but only with children aged 4-8 y. The children’s diet was not found to be a causal factor for this relationship (De Jong et al., 2013).

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However, there was low participation of children with low and middle socioeconomic status.

Therefore, the study population was not representative of the city from which the data was collected.

In contrast to the findings of De Jong and colleagues (2013), a study of the non-advertising screen time and acute eating behaviour in children provided support for a dietary influence (Marsh, Ni Mhurchu, & Maddison, 2013). The study investigated the effects of television, video game play and recreational computer use, all of which did not include breaks for advertisements, on children’s EI. There was evidence that television viewing led to overeating, but only a preliminary indication that screen based behaviours had this same effect (Marsh et al., 2013).

Further evidence of the detrimental effect of television on EI was provided when food intake, total sedentary behaviour and television viewing were measured in 9-11 y old Canadian children (Borghese et al., 2014). In agreement with previous findings of Pearson and Biddle (2011), a negative association was found between the frequency of consumption of healthy foods and television viewing, but not total sedentary time. There was also a positive association with the frequency of consumption of unhealthy foods and television viewing but not for total sedentary time. The researchers suggested that television viewing rather than total sedentary time was more indicative of these dietary patterns of behaviour. In this latter study however total sedentary time was measured by accelerometry which prevented the differentiation of time spent in individual screen based behaviours, including television viewing. The time spent watching television was measured by self-report frequency questionnaire, as was food intake (Borghese et al., 2014). As previously discussed, self-report methods inherently produce mis-reporting owing to recall and social desirability biases (Aresu et al., 2009; Basterfield et al., 2008; Livingstone & Robson, 2000).

More recent research has measured food intake, PA, weight status and screen time (television viewing and computer use) in children aged 11 y (Berentzen et al., 2014). The children whose screen time was >20 h per week were found to consume more portions of snacks per day (1.9 versus mean 1.3 portions) and were less PA (4.3 versus. 4.8 days per week). One extra hour of screen time per week was found to significantly increase BMI by 0.01 z-score and waist circumference by 0.11 cm providing evidence that greater screen time appears to lead to increased

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snacking, lower PA and higher weight status. A limitation of the study however, was that screen time was measured when the children were aged 11 y but the assessment of food intake, PA and weight status was one year later, when they aged 12 y (Berentzen et al., 2014).

The evidence reviewed in this section suggests that during mid-to-late childhood, high screen use becomes more prevalent and low PA more widespread which might stem from less parental influence on PA (Huang et al., 2013). Consequently, an increase in weight status could be due to either or both of these behaviours, collectively (Huang et al., 2013). The negative associations with healthy food consumption and positive associations with unhealthy food intakes during screen time (Berentzen et al., 2014; Borghese et al., 2014; Pearson & Biddle, 2011) add support for a detrimental effect of screen time on PA, EI and weight status, in mid-to-late childhood, especially in boys.