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Reducing children's television viewing to prevent obesity

There is an alarming increase in obesity in this country, especially among children. It has been speculated that television viewing is one of the most easily modifiable causes of obesity among children. Television viewing may reduce energy expenditure and increase dietary energy intake. This randomised controlled school-based trial assesses the effects of reducing television viewing on changes in adiposity, physical activity and dietary intake.

Message

Reduced television viewing and decreased measures of adiposity were seen in children participating in the trial. Reducing television viewing is a promising approach to help prevent obesity in children.

Reference

TN Robinson. Reducing children's television viewing to prevent obesity. Journal of the American Medical Association 1999 282: 1561-1567.

Study

One school was randomly assigned to implement a programme to reduce television, videotape and video game use (92 children participated). Another school was used as a comparison (100 children participated). The schools were matched sociodemographically and scholastically. Children from the two schools were comparable in age (average of nine years), gender and number of television and video players in the home.

The programme consisted of approximately 18 hours of lessons incorporated into the curriculum over six months:

Assessments were performed by staff (unaware of the experimental design) on two occasions, at the start of the study in 1996 and after completion of the programme in 1997. Physical measurements were taken. Children completed self-report questionnaires. Parents were interviewed by telephone. Parents, children and teachers were not aware that the primary outcome was adiposity.

Physical measurements:

Television viewing and physical activity:

Dietary intake:

Results

Participation in the programme varied, e.g. the challenge of not watching television for ten days was managed by 67% of children; 55% limited their viewing/playing to seven hours per week.

The results were adjusted for initial body mass index, age and gender. Physical measurements in children of this age were expected to increase over the course of the trial as part of normal growth. Therefore relative differences were calculated, i.e. changes in children participating in the programme relative to changes in non-participating children.

Effects on Adiposity

Compared with children who did not participate in the programme, participating children had (statistically significant) relative decreases in body mass index, triceps skinfold thickness, waist circumference and waist-to-hip ratio (shown in Table 1).

Table 1. Decreases in physical measurements in participating children relative to non-participating children.

Measurement

Relative decreases (95% confidence intervals)

Body mass index (kg/sq metre)

-0.45 (-0.73 to -0.17)

Triceps skinfold thickness (mm)

-1.47 (-2.41 to -0.54)

Waist circumference (cm)

-2.30 (-3.27 to -1.33)

Waist-to-hip ratio

-0.02 (-0.03 to -0.01)

Effects on Media Use, Diet and Physical Activity

The programme significantly decreased children's television viewing compared with those not in the programme according to both children and parent reports (reductions of about one third from initial assessment). Participating children reported less video game playing than non-participating children (see Table 2). There were no differences in parent reports of video game playing, children and parent reports of videotape viewing and parent reports of overall household television viewing between participating and non-participating children.

The programme significantly decreased the frequency with which children ate meals in front of the television (see Table 2). The programme made no difference to children's snacking in front of the television, or consumption of high-fat or highly advertised foods.

Table 2. Decreases in reported media use and meals in front of the television in participating children relative to non-participating children.

Measure

Start of trial

Completion of trial

Relative decreases (95% CI)

 

Part

Non-part.

Part

Non-part.

Hours of television per week: children reports

15.35

15.46

8.80

14.46

-5.53 (-8.64 to -2.42)

Hours of television per week: parent reports of children

12.43

14.90

8.86

14.75

-4.29 (-5.89 to -2.70)

Hours of playing games per week: children reports

2.57

3.85

1.32

4.24

-2.54 (-4.48 to -0.60)

Meals in front of television (scale 0-3): children reports

2.38

1.84

1.70

1.99

-0.54 (-0.98 to -0.12)

Meals in front of television (0-14 meals): parent reports

3.18

3.53

2.19

3.43

-1.07 (-1.96 to -0.18)

Part = participating, Non-part = non-participating

 

The programme had no effect on children's physical activity levels or physical fitness.

Comment

It is important to realise that the effectiveness of a programme like this can be influenced by many factors, for example its design, how well it was implemented, how many children adhered to it and how much support children received from others (i.e. parents, siblings, peers) to do so. In this case, the programme was carefully designed (e.g. to decrease media use alone without promoting other more active behaviours); adherence levels varied (if they had been higher, greater reductions in adiposity may have been seen); other influences, e.g. quality of implementation, are unknown. There is also the question of how accurate nine-year old children are at estimating their viewing/playing time (this study tried to improve accuracy by giving the children time-estimating exercises before these questions).

While the programme reduced measures of adiposity, it did not make a difference to changes in physical activity, fitness or diet. However, better measures of diet and physical activity are needed for a more accurate assessment of these measures. Further experimental studies with a larger number of children are also needed to confirm these initial promising results that reducing television viewing can help reduce adiposity.