As of yesterday, restrictions come into force on ads for high fat, salt or sugar foods around shows aimed at four to nine-year-olds. Dedicated children's channels will be allowed a 'phasing-in' period, with the full ban in place by the end of the year.
Outlined by Ofcom in November, from January 1 2008 the new rules will also extend to TV shows aimed at children up to 15 years, as well as adult programmes watched by a large number of of under-16s.
An spokeswoman for Ofcom said: "The new rules are one of a wide range of measures aimed at tackling child obesity.
"By reducing the exposure of children to advertising for products that are high in fat, salt and sugar, the advertising restrictions will contribute to wider efforts to promote healthier diets amongst children."
TV channels and the Broadcast Advertising Clearance Centre (BACC) are responsible for ensuring commercials comply with the new rules, while Food Standards Agency guidelines will be used to decide which products are subject to the rules.
Hamish Pringle, director general of the Institute of Practitioners in Advertising, told BBC News 24 he was confident that the ban would not affect the industry too much.
"Yes, advertisers have lost the opportunity to communicate directly to children, [but] they still have the opportunity to talk to their parents," he said.
Ofcom will review the effectiveness and scope of new restrictions in autumn 2008.