WASHINGTON - THE United States is losing its battle against bulging waistlines, with two-thirds of Americans now overweight or obese, according to an annual report released on Wednesday.

In the past year, nearly half of the 50 US states saw obesity rates rise and no state saw a fall in the number of people who were obese, according to the sixth annual 'F as in Fat' report by the Trust for America's Health and the Robert Wood Johnson Foundation.

Obesity is defined as having a body mass index - calculated by dividing a person's weight in kilograms by his or her height squared in meters - greater than 30.

'The country will never be able to contain rates of chronic diseases and health care costs until we find ways to keep Americans healthier,' the report says, pinning more than a quarter of health care costs in the United States on problems linked to obesity.

According to the report, health care costs attributable to Americans' expanding girths are projected to more than double every decade, possibly reaching US$956 billion (S$1.4 trillion) a year by 2030.

That would mean obesity would account for one in $6 spent on health care.

The report also cited other research, which found that obese workers had more than 10 times the number of lost workdays than normal-weight workers - nearly 184 lost workdays per 100 full-time obese employees over a one-year period, versus 14 lost workdays per 100 full-time normal-weight employees.

The southern state of Mississippi held onto the dubious distinction of being the fattest state for the fifth year in a row, with nearly one in three adults and a staggering 44 per cent of children aged 10-17 suffering from obesity, the report showed.

'Mississippi also continues to have the highest rate of physical inactivity and hypertension, and has the second highest rate of diabetes,' the report said.

Diabetes alone accounts for 11 per cent of all US health care costs, according to the report. -- AFP