Obesity numbers rise in 28 states

The number of obese Americans is steadily climbing, with obesity rates rising in 28 states in the past year.

According to a report released Tuesday titled "F as in Fat: How Obesity Threatens America's Future 2010," 38 states have obesity rates of more than 25 percent, and almost one-third of American children are considered obese.

Obesity is defined by body mass index (BMI), a measurement that relates a person's weight to height. For adults, a BMI of 30 or above is considered obese. The definition varies for children according to age and sex, but a child is considered obese in the 95th percentile on the BMI chart.