A raft of tough measures must be introduced if the child obesity crisis is not to get worse, top doctors say.
The obesity crisis is set to get worse, doctors warn
The British Medical Association report called for a junk food ad ban and rules for the nutritional balance of school meals and pre-prepared food.
The BMA warned that without strong action, children would increasingly develop adult diseases such as type 2 diabetes, cancer and bone problems.
The government said it was addressing the issues through voluntary codes.
Worldwide, more than 22 million children under five are severely overweight, while in the UK about one million children under 16 are obese.
If current trends continue, it is estimated at least one fifth of boys and a third of girls will be obese by 2020, the BMA's Board of Science warned.
Dr Vivienne Nathanson, head of science and ethics at the BMA, said the recommendations focus on "preventing childhood obesity".
"There is no room for complacency and it's essential the government listens to what doctors are saying.
"Children are being bombarded with mixed messages.
"On the one hand they might learn about healthy eating at school and they go home and spend hours watching TV and see celebrities eating hamburgers, crisps or drinking fizzy drinks."
The BMA report called for the government to intervene in a range of areas, including schools, the food industry and advertising.
A mandatory nutrient and compositional standard for school meals setting maximum fat, sugar and salt content should be introduced.
And manufacturers should be legally obliged to reduce salt, sugar and fat in pre-prepared meals.
The doctors also called for an outright ban on junk food advertising and sponsorship across all media.
The government should also take proactive measures, including subsidising fruit and vegetables and increase funding to sports and recreation facilities.
The BMA was supported in its call for intervention by the National Union of Teachers, which is demanding a junk food TV ad ban before 9pm.
NUT general secretary Steve Sinnott said: "It is no good relying on self-regulation - it hasn't worked in the past, and there is no reason to believe it will work now."
Obesity expert Dr Andrew Hill, from the University of Leeds, said obesity was not going to be eradicated, and taking action was about "slowing down its increase and perhaps reducing" it.
Food and Drink Federation Deputy Director General Martin Paterson said the industry understood its responsibility in helping to tackle the problem.
But he questioned whether a TV ad ban was the way forward, saying similar initiatives in Quebec and Sweden had had no effect.
A spokeswoman for the Department of Health said the issues were being addressed by the Public Health White Paper, although she acknowledged many of the measures were initially being done through voluntary agreements.
"We are working across government, with the food, leisure and sports industries, and consumer organisations to help children lead healthier lives."