Childhood obesity is a growing concern worldwide. But in New Zealand it’s a particularly pressing issue.

With one of the highest rates^[1] in the OECD, about one in three New Zealand children are overweight or obese. Obesity in children can lead to severe health issues^[2] that persist into adulthood.

While many factors contribute to childhood obesity – such as diet, physical activity and genetics – one often-overlooked factor is screen time.

Children are constantly surrounded by devices such as TVs, tablets and smartphones, and screen time has become a normal part of daily life.

The World Health Organization and the American Academy of Paediatrics both suggest preschool-aged children should have no more than one hour of screen time^[3] daily.

But many young children in New Zealand and overseas are spending significantly more time on screens, with many regularly surpassing these guidelines.

Our new study^[4] explored how simple family screen time rules could reduce childhood obesity risk. Our work revealed ways parents and policymakers can tackle this growing challenge.

Screens and the risk of obesity

Excessive screen time has been linked to various health issues in children^[5], ranging from mental and emotional problems to physical health concerns like obesity.

Spending too much time with screens often means more sitting and less physical activity^[6], both of which can lead to excess weight gain.

Additionally, screen time is associated with snacking^[7], as children often eat while watching shows or playing games. These snacks are typically high in sugar and fat, contributing to weight gain over time.

Advertisements for high-calorie foods are also common in children’s media, increasing cravings for unhealthy snacks.

Moreover, screens emit blue light, which can disrupt sleep cycles^[8] if used close to bedtime. Poor sleep has been shown to increase hunger and cravings for high-calorie foods, making children more susceptible to weight gain.

The World Health Organisation recommends no more than one hour of screen time for toddlers but many New Zealand children are spending much longer with devices than that. Marc Romanelli/Getty Images^[9]

Noticeable benefits from limits

Our research used data from the Growing Up in New Zealand study^[10], which followed over 5,700 children and their families. We examined how family screen time rules established at the age of two influenced obesity risk by the time the children were four-and-a-half.

The results were eye-opening. We found families who set and implemented clear rules about screen use saw noticeable benefits.

These rules indirectly helped reduce obesity risk by supporting better sleep habits and limiting excessive screen use – two factors strongly linked to healthier weight.

While the study didn’t find a direct link between screen time rules and a reduced obesity rate, it did show how these rules can prevent behaviours associated with weight gain.

For example, children in families with screen time rules slept longer and spent less time on screens, both of which are critical for maintaining a healthy weight.

The most effective screen time strategies covered three main areas:

Quality: deciding what type of shows or apps children can use. Previous research recommend prioritising educational or calming media over fast-paced or violent shows, as intense content can overstimulate children, making it harder for them to relax and sleep well.

Quantity: setting a limit on how much time children spend on screens each day.

Timing: establishing rules on when screens are allowed. For instance, avoiding screen time right before bed can help prevent sleep disruption from blue light exposure.

The findings suggest setting all three types of screen rules can make a big difference in helping children form healthier habits. When families combine these rules, it doesn’t just reduce screen time; it also supports better sleep, which is vital for children’s overall health.

Over time, these small but consistent rules can have a lasting, positive impact on children’s physical and mental wellbeing, reducing the risk of developing unhealthy weight.

Other factors

It’s worth noting that screen time habits don’t exist in a vacuum. The study also highlighted how socioeconomic factors can affect screen time and, subsequently, childhood obesity.

Families in financially disadvantaged situations often have fewer resources to manage screen time effectively^[11]. These families might rely more on screens to entertain or occupy children due to limited access to alternative activities or safe outdoor spaces.

Additionally, food insecurity^[12] – a lack of access to affordable, nutritious food – can increase reliance on inexpensive, unhealthy food options, further contributing to childhood obesity.

When we accounted for factors such as poverty and food insecurity, the link between screen time and obesity became less direct. This suggests that tackling childhood obesity effectively requires addressing these underlying socioeconomic factors alongside screen time habits.

Guiding parents

For families, the key advice is to implement and maintain rules that address the quality, quantity and timing of screen use.

These rules encourage children to balance their screen time with other activities, like physical play and adequate sleep, which are essential for healthy growth and development and reduce obesity risk.

Policymakers can also play a role by supporting initiatives that assist families in lower-income brackets.

Policies which reduce poverty, make healthy food more affordable and accessible, and create safe and attractive neighbourhood spaces would all make it easier for parents to establish and follow screen time rules.

With rates of childhood obesity rising and long-term health consequences becoming more apparent, tackling this issue requires coordinated action from families, communities and policymakers alike.

This research was completed with Maryam Ghasemi, Deborah Schlichting, Maryam Pirouzi and Cameron Grant.

References

1. ^{^} one of the highest rates (www.rnz.co.nz)
2. ^{^} can lead to severe health issues (hpi.georgetown.edu)
3. ^{^} no more than one hour of screen time (www.who.int)
4. ^{^} new study (academic.oup.com)
5. ^{^} linked to various health issues in children (pmc.ncbi.nlm.nih.gov)
6. ^{^} more sitting and less physical activity (pmc.ncbi.nlm.nih.gov)
7. ^{^} screen time is associated with snacking (www.lboro.ac.uk)
8. ^{^} disrupt sleep cycles (pmc.ncbi.nlm.nih.gov)
9. ^{^} Marc Romanelli/Getty Images (www.gettyimages.com.au)
10. ^{^} Growing Up in New Zealand study (www.growingup.co.nz)
11. ^{^} fewer resources to manage screen time effectively (pmc.ncbi.nlm.nih.gov)
12. ^{^} food insecurity (pmc.ncbi.nlm.nih.gov)