The Mayor of London, Sadiq Khan, is to ban junk food advertising on public transport in London.
He said he wants to help tackle what he called the ticking time bomb of obesity.
The ban will apply to buses, bus shelters, overground and underground trains.
Tfl, the company that runs public transport in the city, said it supports the mayor's attempts to make London healthier.
The UK capital has one of the highest child overweight and obesity rates in Europe, with almost 40 percent of children aged 10 and 11 being affected.
"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," said Khan.
Doctors say advertising is one of the leading causes of the problem especially in big cities where there is also a high level of deprivation.