Ministers are planning a possible clampdown on the advertising of junk food and drink to children.
Fast food is a particular worry
Culture Secretary Tessa Jowell has asked the new television regulator Ofcom to review its advertising code.
She said she was worried about soaring rates of obesity among children.
And she argued the current rules on food advertising were not strong enough to help combat the problem.
Ms Jowell told BBC Radio 4's World Tonight that banning on advertising high calorie foods during children's programmes could be "disproportionate" to the benefits it would bring.
But she said: "I have written today to the chairman of Ofcom asking him to review the existing code.
"I believe - but it is a judgement that Ofcom will have to make - that the existing code is inadequate and needs to be toughened up."
A review of research by the Food Standards Authority showed advertising was having an impact on children's food consumption, she said.
Ofcom could also look at calls to stop sporting celebrities fronting adverts for fattening foods and drinks.
Ms Jowell said she wanted to ensure that adverts did not make false claims about food.
But work also needed to be done on getting children doing more exercise and raising children's understanding about what they eat.
An official statement from Ms Jowell's department said: "Obesity has to be tackled on a broad front.
"This means placing more emphasis on school sport and active living, promotion of healthy eating, promotion of media literacy and possibly a toughened advertisers code.
"Advertising is only part of the picture. Through its work as an independent regulator, Ofcom would already need to look at the existing advertising code.
"The secretary of state hopes it will be tightened up in the light of the growing evidence, and will in particular reflect the willingness of food manufacturers to promote healthy eating."
The government is keen to replicate the success of Finland, where government campaigns succeeded in raising the proportion of the population who are physically active from 30% to 70%, and cut rates of heart disease and obesity as a result.
Official figures for 2002 show that 8.5% of six-year-olds, and 15% of 15-year-olds are obese.
A spokesman for the Food and Drink Federation, which represents the industry, denied that advertising was a significant factor in the steep rise in obesity levels.
A spokesman told the Guardian newspaper: "There is already a strict code in existence which the food and drink industry has an exemplary record of obeying."
Last week David Hinchliffe, the Labour MP and chairman of the Common's Health Committee, called for fatty foods to carry tobacco-style health warnings.
And an article in the medical journal The Lancet, published last month, suggested celebrity endorsement of junk food is contributing to high rates of obesity, particularly among children.
A report by the Food Standards Agency on advertising of children's food is to be published in the New Year.