The rate of obesity has climbed dramatically in this country during recent decades.
And researchers now attribute it to over-eating rather than a decline in physical activity.
Scientists in Australia used mathematical models to determine that weight gain among Americans is virtually all explained by people simply consuming too many calories.
Researchers say changes in physical activity appeared to play a minimal role.
The study looked at more than 23-hundred adults and children.
Although researchers say exercise is obviously important, they say public health policy may need to focus more on encouraging people to eat less.