On 10 November 2020, the UK government launched a consultation for a total ‘junk’ food online advert ban. The proposed rules, following on from a broader anti-obesity strategy published earlier in the year, surprised many for being far tougher than expected.


All of this sound and fury, after years of relative inaction, was thought to have resulted from Prime Minister Boris Johnson experiencing a Damascene conversion after he was hard hit by COVID-19, the severity of which he blamed on his elevated weight.

Obesity is indeed one of the biggest public health crises the UK faces, with almost two-thirds of adults in the UK either overweight or living with obesity. Crucially, one-third of children leave primary school overweight or with obesity, making them more likely to become adults carrying excess weight.

What the pandemic has crystallised for many, including our PM, is that living with obesity increases your risk for a number of different diseases, infectious or otherwise. Hence this far-reaching proposed ban of all online adverts promoting ‘junk’ food high in fat, sugar and salt (HFSS), with the explicit aim of helping protect children from developing long-term unhealthy eating habits.

More like this

So what is the evidence that such an intervention would be effective?

Read more about obesity:

Well, in October 2020, my colleagues from the Centre for Diet and Activity Research (CEDAR) at the University of Cambridge, estimated that banning unhealthy food advertising on television before the 9pm watershed meant that children in the UK would see, on average, 1.5 fewer HFSS advertisements per day. They calculated that removing these had the potential to reduce the number of UK children with obesity by 40,000 and those who are overweight by a further 80,000.

This research however, only examined TV adverts; and anyone with teenaged (or younger) offspring will know they hardly watch any linear TV. Most children today stream much of their video online, where it is estimated that 59 per cent of food and drink adverts are for HFSS products.

I am actually surprised that the number is not higher. When was the last time you saw a food advert (online or otherwise) for broccoli, or cabbage, or beef, or tofu? Instead, the majority of ads will be for major restaurant chains and for pre-packaged foods, with the total size of the online HFSS food and drink advertising market estimated at around £438m.

In addition, accessing content online also renders the concept of a ‘watershed’ moot, thus the proposed banning of ALL such online adverts.

Unsurprisingly, many big beasts in the food industry are pushing back hard on this. A number of manufacturers and brands, including Mars and Kellogg’s, have a written to the government seeking more time to respond to the consultation, arguing that the plans would disproportionately hit small- and medium-sized business.

They cite, as an example of this, a hypothetical local wedding cake business, potentially being unable to share product details on its Instagram account. If true, this would be a fair point.

However, I’m certain the regulators would be able to differentiate between a multi-national corporation advertising burgers or pizzas and ‘Wilma’s Wonder Wedding Cakes’ from the local high street promoting their tiered sponge confectionery.

Here is the bottom line. Children, if left to their own devices (pun fully intended), are likely to seek out the foods that are high in calorie density (fat and sugar). This is an evolutionarily conserved trait to ensure a small helpless mammal grows as quickly as possible to reduce their chances of becoming tiger food. We, as a society, are therefore duty-bound to protect our children, whatever size they are, from the choices they are hardwired to make in this current food environment.

Read more from Reality Check:

Crucially, research suggests that such an online advert ban will be most beneficial to children whose parents earn the least (and are therefore at increased risk of obesity and other diet-related illnesses), compared to those who earn the most, thus additionally playing a role in reducing socioeconomic health inequalities.

As with most things, the devil is, of course, in the detail. What will fall under the HFSS umbrella? At the time of writing, this was still not clear. Also, what would constitute a ‘successful’ intervention?

We must resist eye-catching, but ultimately crude, short-term outcomes such as ‘did it single-handedly reduce obesity?’, that sets the intervention up for perceived failure. What will be required is high-quality independent evaluation that should measure multiple health and societal outcomes. This will take time and require patience – a trait lacking in most humans.


The causes of obesity are complex, encompassing a myriad of interacting biological, environmental and socioeconomic factors. Thus, a comprehensive approach is needed to address all the drivers that influence health and weight, including a non-hysterical and sober discussion of food advertisement that targets children.

Giles is a geneticist at the University of Cambridge, whose research focuses on food intake, genetics and obesity. He is a presenter on Trust Me, I’m A Doctor, and his latest book is Gene Eating: The Story Of Human Appetite (£14.99, Orion Spring). 
Visit the BBC's Reality Check website at bit.ly/reality_check_ or follow them on Twitter @BBCRealityCheck


Giles is a geneticist at the University of Cambridge