WASHINGTON: More than a quarter of all Americans are now obese, the latest US government figures show. The percentage of US adults who are obese grew by nearly 2 per cent between 2005 and 2007, from just under 24 per cent to 25.6 per cent, the Centres for Disease Control and Prevention reported late on Friday.

Alabama, Mississippi, and Tennessee had the worst rates, with 30 per cent of adults reporting weights that made them medically obese. Colorado had the slimmest population, with 18.7 per cent of people reporting weights that put them in the obese category.

Obesity is defined as having a body mass index or BMI of 30 or above. BMI is calculated using height and weight. For example, a 5-foot, 9-inch (175 cm) tall adult who weighs 203 pounds (92 kg) would have a BMI of 30.

BMI takes into account variations in build for all but the most heavily muscled athletes. “The epidemic of adult obesity continues to rise in the United States indicating that we need to step up our efforts at the national, state and local levels,” said Dr William Dietz, director of the CDC’s Division of Nutrition, Physical Activity, and Obesity.

“We need to encourage people to eat more fruits and vegetables, engage in more physical activity and reduce the consumption of high calorie foods and sugar sweetened beverages in order to maintain a healthy weight,” Dietz said. CDC researchers used data from the Behavioural Risk Factor Surveillance System, an annual telephone survey of more than 350,000 adults. Southerners are the heaviest Americans, on average, with 27 per cent obese.