TV in bedroom 'risk factor' for child obesity

“Children who have TVs in their bedrooms are more likely to be overweight than those who do not,” BBC News reports. A UK study found a link between children having a TV in their room and an increased risk of obesity.

Researchers followed children from seven to 11 years old to see whether the number of hours watching TV, playing on the computer or having a TV in the bedroom influenced the risk of having higher body fat in a couple of years.

It found that, compared to children who didn’t have a TV in their bedroom at age seven, children who did had a significantly higher body mass index (BMI) and body fat at the age of 11. The association was higher for girls than boys.

Although this is an interesting study with potentially useful findings, it cannot prove there is a direct connection between using screens and body weight. But it would seem plausible that at least some children who spend a lot of time staring at a screen are not meeting the recommended levels for physical activity.

Almost a fifth of UK children are obese. As the study itself puts it: “Ironically, while our screens have become flatter, our children have become fatter.”

Read more advice about helping your child to become more active and what to do if you are worried your child is overweight.

Where did the story come from?

The study was carried out by researchers from University College London (UCL) and was funded by a grant from the Economic and Social Research Council. The study was published in the peer-reviewed International Journal of Obesity.

Generally, UK media coverage on this study was accurate.

What kind of research was this?

This was an analysis of data obtained from a large prospective ongoing cohort study: the UK Millennium Cohort Study, which aimed to assess long-term associations between television and computer use and body fat in children.

In the UK, out of all screen based media, TV remains the most popular amongst children aged five to 11. Concurrently, the prevalence of obesity in childhood continues to increase.

The researchers wanted to investigate the link between TV use and obesity in children by following children over a period of time – between the ages of seven and 11.

Cohort studies such as this are useful for evaluating potential links between exposure and outcome. However, due to the study design it isn’t always possible to fully rule out the influence of other confounding factors such as diet and physical activity. Therefore confirmation of cause and effect between the two variables can’t be proven.

What did the research involve?

Researchers analysed data on 12,556 children from the UK Millennium Cohort Study (MCS). The Study is a prospective cohort study which follows children born between September 2000 and January 2002 in all four countries of the UK.

The dataset is nationally representative of the UK general population and includes children from economically disadvantaged areas and different ethnic minorities.

This analysis specifically looked at the data for 12,556 children (6,353 boys and 6,203 girls) who had been followed from the age of seven until 11. Two outcome variables were assessed: use of screen based media and body fat in children.

Body fat

Body fat at the age of 11 was measured using three indicators:

• body mass index (BMI)
• fat mass index (FMI) – total fat mass divided by height squared to reveal the amount of fat in the body
• overweight – based on specific International Obesity Task Force (IOTF) criteria

Screen-based media

The use of screen-based media was measured in children at age seven. Three indicators were used:

• whether the child had a bedroom TV
• number of hours spent watching TV or DVDs
• number of hours spent playing on the computer

The following confounding factors were adjusted for:

• child age
• child BMI at nine months old and three years old
• breastfeeding duration
• child ethnicity
• maternal BMI
• maternal education
• family income

The researchers then analysed the data to look for any associations between screen-based media use and body fat in children.

What were the basic results?

This study had some interesting background findings:

• at the age of seven, 55% of boys and 53% of girls in the sample had a TV in their bedroom
• at the age of eleven, 25% of boys and 30% of girls were found to be overweight

Overall in this sample, compared to children who didn’t have a TV in their bedroom, those who did have a TV in their bedroom at age seven had a significantly higher BMI and FMI at the age of 11. The associations were higher for girls than boys.

Additionally, following regression analysis (a statistical tool used to estimate the relationship between different variables), children who had a TV in their room at the age of seven had a higher relative risk of being overweight at age 11. The associations were stronger for girls.

• Girls: Relative Risk [RR] 1.31; 95% Confidence Interval [CI] 1.15 to 1.48
• Boys: RR 1.21; 95% CI 1.07 to 1.36

How did the researchers interpret the results?

The researchers concluded: “Our longitudinal analysis has shown that having a TV in the bedroom is an independent risk factor for increased body fatness in this nationally representative sample of UK children.

“Girls who had a TV in their bedroom at age 7 were at an approximately 30% higher risk of being overweight at age 11 compared to those who did not have a TV in their bedroom, and for boys the risk was increased by about 20%.”

Conclusion

This analysis used data from the UK Millennium Cohort Study to assess for long-term associations between television and computer use and body fat in children.

It found that compared to children who didn’t have a TV in their bedroom at age seven, children who did had a significantly higher BMI and FMI at the age of 11. The association was higher for girls than boys.

This is an interesting study however there are a few points to note:

• Although the researchers adjusted for potential confounding factors, diet and physical activity were not adjusted for. An unhealthy diet and lack of physical activity are two of the biggest contributors to obesity so it’s surprising that these weren’t looked into. It’s quite likely that children who spend a large amount of time in front of screen-based media don’t spend quite as much time getting exercise outdoors or through team sports etc. However as we don’t have data on the level of physical activity of these children, we are unable to make that conclusion either.
• Interestingly, the dataset for the MCS represented different ethnicities but in this particular analysis 84.6% of the children were white. Genetics and cultural differences do have an impact on children’s behaviours so it would have been interesting to see whether children from different ethnic backgrounds had different results.

Overall this study doesn’t prove that watching TV or having a TV in your bedroom directly increases body fat. However, the link between increased sedentary time in general, along with low physical activity and poor diet, and overweight and obesity is quite well established.

Current guidelines recommend children and young people need to do at least 60 minutes of physical activity every day.

Read more about how to help your child get more active.

Links To The Headlines

TVs in children’s bedrooms ‘increase risk of obesity’. BBC News, June 2 2017

TVs in the bedroom linked to childhood obesity, study finds. The Guardian, June 2 2017

Children with TVs in their bedroom have a higher risk of becoming obese – and it’s worse for girls, study finds. Daily Mail, June 2 2017

Links To Science

Heilmann A, Rouxel P, Fitzsimons E, et al. Longitudinal associations between television in the bedroom and body fatness in a UK cohort study. International Journal of Obesity. Published online June 1 2017