By Michael Buchanan
BBC correspondent in Washington
A new study in the United States says obesity is likely to become the country's biggest preventable killer.
The US government is trying to encourage Americans to exercise
The research, by the Centers for Disease Control and Prevention, is the latest work showing widespread weight gain among Americans of all ages.
"We're just too fat," Health Secretary Tommy Thompson said at the unveiling of the study.
It found that poor diet and lack of exercise caused 400,000 deaths in the US in the year 2000.
That figure represents a 33% jump since 1990.
Fast food 'lifestyle'
If current trends continue, then obesity will shortly overtake smoking as the single biggest cause of preventable deaths in the United States.
Overweight people, says the research, are more likely to suffer heart disease, cancer, strokes and develop diabetes.
Several overweight teens recently tried to sue the McDonald's fast food chain
Two-thirds of US adults and nine million children are either overweight or obese.
This is the result of a fast-food lifestyle, increased use of computers and less physical activity.
The release of the study coincides with a new government drive to encourage Americans to do more exercise.
But critics say greater emphasis should be put on telling people to simply eat less and argue that the administration is frightened of antagonising the multi-billion-dollar fast-food industry.
As if to confirm their fears, as the study revealed a fattening nation, the House of Representatives announced that it plans to push for a bill that would limit "frivolous" lawsuits which accuse fast food chains of causing obesity.
Several teenagers recently tried to sue the McDonald's fast food chain, claiming its products made them fat.
Their case was thrown out and, as one supporter of the bill says, "frivolous lawsuits will not make anyone thin".