The government's record on tackling obesity has been described as "woefully inadequate" by MPs, the BBC has learnt.
Youngsters are bombarded with junk food ads, report says
A report by a House of Commons cross party committee of MPs is due to be published on Thursday.
A late draft, seen by BBC Radio 4's Today programme warns the £3.5bn annual cost of obesity could threaten the end of a publicly funded health service.
It also severely criticises government ministers in dealing with what MPs call an epidemic of obesity.
The comprehensive report warns of increased levels of diabetes, cancer and heart diseases if obesity rises.
An estimated one in four men and one in five women are obese.
The number of obese children has doubled over the past 20 years. One in 10 six-year-olds and one in six 15-year-olds are now obese.
The government has said it will not comment on the specifics of a leaked report.
The report cites the case of an obese three-year-old who died of heart failure. It says this kind of case is rare, but warns it is a portent of things to come.
The MPs say the NHS does not appear to understand how serious the issue of obesity is - and what effect it could have on the health service.
Seven government departments are criticised in the report, which accuses the government of failing to formulate joined up policies on obesity that link food, transport, education, health and work.
The Department of Transport comes in for scathing criticism.
It has allowed pedestrians and cyclists to be swept aside during two generations of cities being reshaped to suit car drivers, the MPs say.
The committee says children have been bombarded with junk food advertisements, fed bad school meals and sold fizzy drinks from school vending machines.
MPs are angry that ministers have used slogans coined by the food industry and supported junk food promotions in schools.
The food industry is the subject of severe criticism in the report - particularly for campaigns which encourage children to "pester" parents for junk foods.
Measures which may appear in the final report could include a "traffic light" system to label healthy and unhealthy foods.
Treatment is key
Dr Ian Campbell, chairman of the National Obesity Forum, said: "It is crucial that we implement strategies for the prevention of obesity, and particularly focus on children."
But he said it was equally important to look at how obesity could be treated.
Dr Campbell added: "There isn't one single measure that would have a huge impact. It's a complex disorder."
Dr Frankie Phillips of the British Nutrition Foundation said: "We need to do something about it before it gets just too late.
"The individual has to take some responsibility - you go and choose what food to eat and what activities to do."
But she said a wide range of bodies needed to take their share of the responsibility; the food industry, government - even local town planners, who could make roads safer so people can walk their children to school and employers who could install showers so workers could cycle to work.
She added: "But we shouldn't victimise people for eating what they enjoy.
"We always come back to moderation, and looking at ways of having a balanced diet and being more active."
Health minister Melanie Johnson told the BBC the government was working to tackle obesity, citing this summer's public health White Paper.
She added child nutrition was key: "It's important we get things right for children, that's something we've recognised."
Ms Johnson said the government was looking at ways to improve children's diets in school and at home.
She said the food industry could do more. "Sometimes it has been a bit slow. And if we could get things clearly labelled, it would help an awful lot."
Shadow Secretary of State for Health and Education, Tim Yeo said: "The government's approach to tackling obesity has been disastrously muddled."