Being overweight or obese is the biggest cause of cancer after smoking.

And with worryingly high levels of obesity in children, there’s a chance that weight could one day challenge tobacco for this dubious top spot.

So to mark the first ever World Obesity Day, we’ve been exploring how junk food marketing affects our diet – particularly in children – and how this relates to obesity and cancer.

Tackling obesity is of huge importance, especially in kids

It’s important to note that there isn’t a clear relationship between being too heavy as a child and an increased risk of childhood cancer. But, as the graphic below shows, being obese could be behind up to 10 types of cancer in adults. This adds up to over 18,000 cases of cancer every year, including two of the most common – breast and bowel – and three of the hardest to treat – pancreatic, oesophageal and gallbladder cancer.


It isn’t guaranteed that children who carry excess weight in school will remain overweight as they become adults. But as they grow beyond the classroom, evidence tells us that children who are overweight can be more likely to continue carrying excess weight as adults, putting them at increased risk of cancer.

And given this risk is preventable, we are interested in measures from Government which can help children maintain a healthy weight, to reduce their risk of developing a cancer in their lifetime.

Children’s obesity: a worrying health issue which starts early

One in five children is overweight or obese when they start primary school. And by the time they leave, this goes up to one in three. And while these figures have shown recent signs of slowing, there is no sign that rates are falling.

What’s more, children’s obesity is starkly linked to social and economic deprivation. In our primary schools, children in both the youngest and oldest classes from the most deprived backgrounds are twice as likely to be overweight or obese as their classmates from the least deprived areas.

The Government has acknowledged just how serious this challenge is, with Secretary of State for Health, Jeremy Hunt, describing childhood obesity as a ‘national disgrace’ at last week’s Conservative Party Conference. It plans to launch a new strategy to tackle childhood obesity in the coming months, which we look forward to seeing.

So what leads to children’s obesity, and what can we do about it?

The ‘obesogenic environment’ is complex

Put simply, obesity is caused by taking in more calories through diet than we expel through physical activity. This is also influenced by a person’s metabolism, and is known as the ‘energy balance’. A ‘negative’ energy balance means you take in fewer calories than you burn.

But the more common flipside is having a ‘positive’ energy balance, which usually means people gain weight, as they take in more calories than they use.

There are many factors behind why children become obese. These include, but are not limited to, a child’s diet, the amount of physical activity they do – including how they travel to and from school – and whether their parents are obese. This complex web is known as the ‘obesogenic environment’.

But just because this web is complicated, it doesn’t mean it can’t be changed. And we think changing what children are exposed to on TV – by introducing a ban on TV junk food advertising before the 9pm watershed – is a great place to start.

The not-so-silent salesman: Kids and TV junk food advertising

How food is promoted to children has been found to clearly influence which products they choose to buy and prefer to eat, and this is dominated by TV advertising.

Often, this influence happens without kids even realising. International evidence shows that children – particularly those younger than 8 – don’t recognise the persuasive nature of adverts and only develop the ability to critically judged this type of marketing once they reach age 11 or 12. And a range of tactics are used to market foods to children in the UK, including promotional characters, celebrities endorsing a particular product, premium offers, and website promotions.

Because of the combination of children being influenced to buy junk food, often without realising it, and the strikingly high levels of childhood obesity, we support a pre-9pm watershed ban on junk food being marketed on TV. This will help to reduce the amount of unhealthy food children are exposed to on a daily basis.

Of the huge quantity of adverts we watch on TV every day, adverts for foods high in fat, sugar and salt are much more prevalent than those for healthier alternatives. And when we know that children spend an average of 14.6 hours watching television every week – more time than on any other type of media – it’s no surprise this has an impact on their diets.

Things aren’t working right now

A few restrictions on how foods high in fat, sugar and salt are advertised do already exist. But these only apply to TV shows and channels registered as children’s programming.

While this sounds sensible, it’s ineffective in practice.

The prime viewing hour for children watching TV is between 8 and 9pm, yet shows at this time are typically registered as adult or family programming. And of all the adverts shown during adult or family programming, more than one in five are for junk food, according to early research findings. This means despite the current rules to protect children from junk food marketing, children are still far too easily exposed to these ads on TV.

So we think that extending the regulations to a pre-9pm watershed ban on junk food advertised across all programming is required. We think this will limit their exposure to advertising of unhealthy food on TV and make life easier for parents who want their children to eat healthily.

It’s complicated, but this is a start

Because obesity is complicated, it’s important that the Government’s upcoming childhood obesity strategy takes a comprehensive approach to tackling it. This means that a range of measures that address lots of issues together is likely to be more effective than any single interventions on their own.

Restricting junk food marketing on TV is not a silver bullet for children’s obesity. But because it has such a clear impact on what foods children prefer and choose to buy – often without even realising it – a pre-9pm ban on TV junk food advertising should be one measure that’s central to any strategy.

Children don’t have to be obese. The Government should take comprehensive action before this control is lost.

Dan Hunt is a policy adviser at Cancer Research UK