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Today is National Eat What You Want Day in the US — and the internet has run amok with chocolate cakes, cheese boards, and one rather fetching strawberry pavlova.

But London mayor Sadiq Khan has broken through memes of Joey from “Friends” with an important proposal to reduce childhood obesity.

Khan is set to ban junk food adverts on all public transport around London.

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Transport for London (TfL) — the network which manages all tubes, trams, and buses around the capital — will no longer accept adverts that promote food and drink high in fat, salt, or sugar, as measured by the Food Standards Agency’s nutrient profiling model.

Over a billion people ride the tube every single year, with over £20 million in revenue raised by food and drink advertising on TfL in 2016/17. Over two-thirds of that promoted the types of food and drink that Khan wants to avoid. But he’s hopeful larger companies can simply be persuaded to start advertising healthier products.

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It’s part of a new London Food Strategy, published on Friday, which also includes stopping hot takeaways opening within 400 metres of schools.

The Mayor of London @SadiqKhan proposes a ban on junk food adverts on the entire Transport for London network pic.twitter.com/GSzm0I5AKy — Sky News (@SkyNews) May 11, 2018

Globally, there are 2 billion overweight adults, according to the Global Nutrition Report 2017, and 41 million obese children.

And in London, child obesity is among the highest in Europe. City Hall said that 40% of 10 and 11-year-olds in the capital are obese — and the problem is far worse in poorer communities. For example, young people in east London communities like Barking and Dagenham are nearly twice as likely to be overweight as those out west, like Richmond-upon-Thames.

The ban is currently undergoing a consultation, according to the Guardian.

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Khan called the obesity crisis a “ticking timebomb,” and challenged the government to do more.

“If we don’t take bold steps against it we are not doing right by our young people as well as placing a huge strain on our already pressurised health service in years to come,” Khan said. “It can’t be right that in a city as prosperous as London that where you live and the income you have can have a massive impact on whether you have access to healthy, nutritious food and your exposure to junk food advertising.”

It comes a month after the sugar tax was launched on soft drinks manufacturers to further tackle obesity. Teenagers get over a quarter of their sugar intake from soft drinks — consuming enough to fill a whole bathtub of sugar per person every year.

Good to speak to @GMB viewers this morning about today’s junk food ad ban announcement & to outline what we’re doing to tackle violent crime in the capital. https://t.co/OnaYzHyYcj — Sadiq Khan (@SadiqKhan) May 11, 2018

British Prime Minister Theresa May published a national obesity plan in August 2016, but many campaigners argued it had been “watered down,” and the British Medical Association said the government had “rowed back” on promises. The House of Commons Health Committee agreed, and said it fell short by excluding any restrictions on food and drink marketing.

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Now, however, there are talks underway to reform the plan, which may include a television advertising ban on unhealthy food and drink after 9pm and a restriction on “buy-one-get-one-free” deals on junk food.

Celebrity chef Jamie Oliver, who worked on the initial obesity plan with former Prime Minister David Cameron, was full of praise for Khan, calling the London advert ban “big, bold, brave action” and a “lesson in how to lead.”

#Londoners today @MayorofLondon@SadiqKhan says he has #AdEnough He plans the first junk food advert ban across ALL London’s buses, bus-stops & tubes to tackle #ChildhoodObesity It takes big, bold, brave action & today Sadiq & his team have done that. It's a lesson in how to lead pic.twitter.com/WkMESbxEB5 — Jamie Oliver (@jamieoliver) May 11, 2018

“The evidence is clear that, although it is not a silver bullet, restricting the amount of junk food adverts children are exposed to will help reduce obesity,” said Professor Dame Sally Davies, England’s chief medical officer. “Children are inundated with adverts for unhealthy food so this is a really encouraging move and a bold step in the right direction.”

Global Citizen campaigns to achieve the UN’s Global Goals, which include action on global health and good nutrition. You can join us by taking action on these issues here.