Sugar levels are set to be reduced by food and drink giants as they vow to cut the nation's calorie consumption.

And on top of shrinking the size of popular products to bring them in line with healthy-eating guidelines, ads targeted at the under-16s will also be avoided.

On Friday Kellogg's committed to cutting more than 723 tons of sugar from its cereals in 2017, including Frosties and Coco Pops - but would not specify the amounts this would be by.

To tackle the country's growing childhood obesity crisis, Prime Minister David Cameron will decide next week whether to start talks on introducing a fizzy drinks sugar tax.

In a soft drinks industry-wide pledge to slash levels of the sweet stuff, companies have promised to cut sugar consumption by 20% by 2020.

Coca-Cola cut calories in its drinks by 5% in 2014 and is promising another drop of 5% over the next nine years.

But it is understood that the seven teaspoons of sugar in a 330ml can of Coke will remain the same.

Makers of Tizer, AG Barr, are aiming to slash its calories content by 5% this year, while makers of Lucozade and Ribena are working to reduce calories per 100ml by 20% on average across its drinks portfolio by 2025.

Pepsi and Britvic will also be axing billboards near schools and will ban TV adverts aimed at children.

Leading the calls for a sugar tax on fizzy drinks to help tackle childhood obesity is TV chef, Jamie Oliver - last year he urged ministers to be "big and bold" by introducing the levy.

It is thought a 20% tax could raise more than £1 billion in a 12-month period. Next week advisers at Number 10 will circulate a draft of their plans.

Industry giant Unilever also announced on Friday that it was cutting back the size of single-serving ice creams, including Ben & Jerry's, Magnum and Cornetto.

The move is said to be designed to help consumers make healthier choices as part of a balanced lifestyle and will come into action in spring this year.

Noel Clarke, brand building director for ice cream, Unilever UK & Ireland, said: "It was important there be no compromise to taste or quality and that's exactly what we've delivered.

"Our products will still taste as good as ever, but through a process of development and resizing we will ensure our entire single-serve ice cream portfolio will contain 250 calories or fewer."

A spokesman for Coca-Cola Great Britain said they have also cut their serving sizes, introducing a smaller 250ml can of Coca-Cola, as well as putting the Government's colour-coded traffic light nutrition labels on all cans and bottles.

In a multimillion-pound investment to reduce sugar and calories in drinks such as Sprite, Dr Pepper and Fanta, they have cut sugar content by at least 30%, alongside increasing their marketing investments for their no-sugar alternatives.

"Our actions have helped reduce our consumers' sugar and calorie intake - the Sprite and Dr Pepper reformulations alone each removed more than 10 billion calories and 2,500 tonnes of sugar from the nation's diet," the spokesman said.

"Latest data shows that these actions are making a difference - sugar taken home from soft drinks has declined by 10% over the last four years and sales of diet and no-sugar soft drinks are increasing.

"We have committed a further £15 million in reformulation over the next three years to help reduce the sugar and calories in our drinks even further and we fully support the British soft drinks industry's commitment on further sugar and calorie reduction."