New estimates suggest US children are consuming 200 more calories a day than they were in the 1970s and also weigh five kilograms more than 30 years ago.

Food companies and lack of government action are largely to blame for "unacceptably slow" progress towards tackling obesity, according to experts.

New estimates published in The Lancet medical journal suggest children in the US are consuming 200 more calories a day than they were in the 1970s.

They also weigh five kilograms more than they did 30 years ago.

The extra eating was said to bring in $US20 billion ($A25.6 billion) a year to the US food industry, illustrating the difficult conflict between health and economic priorities.

A series of papers in The Lancet highlighting the problem of obesity and what needs to be done to overcome it points an accusing finger at food companies.

The authors claimed that the food industry has a "special interest" in targeting children.

Repeated exposure to processed foods and sweetened drinks during infancy built taste preferences, brand loyalty and high profits, they claimed.

This year the global market for processed infant foods was likely to be worth $US19 billion compared with $US13.7 billion in 2007.

Yet, few countries had taken regulatory steps to protect children from the harmful effects of obesity or implemented widely-recommended healthy food policies.

Most had relied solely on voluntary moves by the food industry, with no evidence of their effectiveness, said the authors.

"Our understanding of obesity must be completely reframed if we are to halt and reverse the global obesity epidemic," said Dr Christina Roberto, one of the researchers from the Harvard TH Chan School of Public Health in the US.

"On one hand, we need to acknowledge that individuals bear some responsibility for their health, and on the other hand recognise that today's food environments exploit people's biological (eg, innate preference for sweetened foods), psychological (eg, marketing techniques), and social and economic (eg, convenience and cost) vulnerabilities, making it easier for them to eat unhealthy foods.

"It's time to realise that this vicious cycle of supply and demand for unhealthy foods can be broken with 'smart food policies' by governments alongside joint efforts from industry and civil society to create healthier food systems."