New research shows that American people have become more active over the last decade, although these improvements have done little to stem the nation's obesity problem.

In more than two-thirds of the nation's counties, men and women have both increased their exercise levels according to The State of Health in the United States report by the University of Washington.

For every one per cent increase in physical activity, prevalence of obesity fell by just 0.11 of one per cent.

Between 2001 to 2009, obesity rates for men and women have fallen in just nine of 3,007 counties in the United States.

More than one third of adults in the US and approximately 17 per cent of children are obese, according to the federal centre for disease control and prevention.

Health experts have said that increased levels of exercise and a change in diet could be a major factor in bringing down those numbers but despite the findings, American life expectancy has risen from 75.2 years in 1990 to 78.2 years in 2010.

According to the study, changes in a county's income, educational attainment and insurance coverage, did not show a correlation to life expectancy - suggesting that shifts in behavioural drivers of disease, such as diet, exercise and obesity are more important.

To read more on the report click here