Obesity specialists say society must stop seeing the condition as an individual's "failing" and act to help people live more healthily.
Experts say the whole family has to be treated to help a child lose weight
Doctors at the National Obesity Forum conference in London called for smaller portions and play areas for children.
Professor Thomas Wadden, of Pennsylvania University, said: "People, particularly children, are being 'swept along' with the environment."
The government is set to address obesity in a forthcoming White Paper.
Another specialist at the conference, Professor Philip James, head of the International Obesity Task Force, accused the government of doing nothing to tackle rising rates of obesity, despite growing concerns.
Professor James said: "Despite warnings by the Chief Medical Officer two years ago that the problem was accelerating, the government has done nothing. This is reprehensible.
"If the government doesn't act decisively in carving out a coherent public health programme tackling this problem, they will be failing the nation."
Professor Wadden said: "Obesity is always treated as if people have a lack of will-power.
"But we live in a society where there is a high-fat, high-sugar diet and low physical activity."
He said 65% of the US population was obese or overweight, and in the UK, around 22% of adults are obese and the same proportion again are overweight.
"It's an epidemic where everyone is being affected.
"We have to make it easy for people to make the right choices."
He said children had to have access to physical exercise in school, and at home - by making play areas available and safely accessible.
Professor Wadden added: "There also has to be a campaign aimed at decreasing the amount of television children watch and the amount of video games they play."
Industry, the government and health experts had work together to help people live healthily, he said.
But he said part of the problem was a failure of people to accept obesity as a condition.
"It's one of the last remaining acceptable prejudices. But in fact, it's an acceptable condition.
"Even within the NHS, physicians could do more to help people who are overweight and obese.
"Patients can find it very difficult to talk about their weight. There is still a lot of stigma and shame."
Dr Julian Shield, a diabetes and metabolism specialist at the Royal Bristol Children's Hospital who runs a childhood obesity clinic, said the condition was linked to a range of other illnesses such as Type 2 diabetes in the young.
But he said treating children through such clinics, was effective.
"We can get people to lose weight as long as they engage with the clinic's work, although you do need to engage the whole family to have any impact on the child."
But he added "there are very few clinics doing this work in the NHS."