Individuals can no longer be held responsible for obesity and government must act to stop Britain "sleepwalking" into a crisis, a report has concluded.
The largest ever UK study into obesity, backed by government and compiled by 250 experts, said excess weight was now the norm in our "obesogenic" society.
Dramatic and comprehensive action was required to stop the majority of us becoming obese by 2050, they said.
The government pledged to draw up a strategy to address the issue.
But the report authors admitted proof that any anti-obesity policy worked "was scant".
Nonetheless, they said every level of society, from individuals to the upper echelons of government, had to become involved in the campaign against a condition which carried such great social and economic consequences.
In 2002, those who were overweight or obese cost nearly £7bn in treatment, state benefits and indirect costs such as loss of earnings and reduced productivity.
In 40 years' time, that figure could reach nearly £46bn, as health services struggle to cope with the ill-health such as type 2 diabetes, cancer and stroke which can be associated with excess weight.
An obese person dies on average nine years earlier than somebody of normal weight, while a very obese person's life is cut short by an average of 13 years.
"There is a danger that the moment to act radically and dramatically will be missed," said Sir David King, the government's chief scientific adviser and head of the Foresight Programme which drew up the report.
"It is a problem that is getting worse every year."
Dr Susan Jebb of the Medical Research Council said that in this environment, it was surprising that anyone was able to remain thin, and so the notion of obesity simply being a product of personal over-indulgence had to be abandoned for good.
"The stress has been on the individual choosing a healthier lifestyle, but that simply isn't enough," she said.
From planning our towns to encourage more physical activity to placing more pressure on mothers to breast feed - believed to slow down infant weight gain - the report highlighted a range of policy options without making any concrete recommendations.
Industry was already working make healthier products available, the report noted, while work was advanced in transforming the very make-up of food so it was digested more slowly and proved satisfying for longer.
But Sir David said it was clear that government needed to involve itself, as on this occasion, the market was failing to do the job.
Health Secretary Alan Johnson described the report as "nothing, if not challenging" and said a national debate was needed about the best way forward.
He said a cross-government strategy would be developed to respond to the challenge of obesity.
He said: "As this report starkly demonstrates, people in the UK are not more gluttonous than previous generations and individual action alone will not be sufficient.
"Solutions will not be found in exhortations to greater individual responsibility or in the futility of isolated initiatives."
Public Health Minister Dawn Primarolo said it was too early to say whether the same "shock" approach seen in public health warnings against smoking would be adopted with obesity, or whether a tax on fatty foods, highlighted in the report but widely dismissed as unworkable, would be considered.
"The most important thing is there has to be public consent and understanding of the issues you're trying to challenge," she said.
"A mandate for change will be difficult because it has to be preceded by an understanding of the dangers of obesity."
She said the main aim now was to reduce the proportion of overweight and obese children to 2000 levels by 2020.
But the British Heart Foundation (BHF) accused the government of backtracking on promises, saying this was a "softer, more distant" target than one originally proposed - to halt childhood obesity rates by 2010.
But the Royal College of Physicians said it thought the report was "encouraging".
"The emphasis on cross-governmental initiatives is particularly welcome, as is the importance of addressing issues across society whilst avoiding blame," said its president, Professor Ian Gilmore.
The Food and Drink Federation said it understood its role in tackling the problem.
"Our industry is now widely recognised as leading the world when it comes to reformulating products; extending consumer choice; and introducing improved nutrition labelling," a spokesperson said.
Andrew Lansley, the Shadow Health Secretary, said: "The government has been asleep for the last decade while the alarm bells have been ringing."
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