Americans are spreading out, but in the wrong direction - at the waist line.

At least 20 percent of adults are obese in every state, according to data from the Centers for Disease Control and Prevention (CDC).

In four states - Alabama, Louisiana, Mississippi and West Virginia - more than 35 percent of surveyed adults were obese, the CDC reported on Sept 1 in maps that show the prevalence of obesity among states.

In four other states - Minnesota, Montana, New York and Ohio - obesity figures decreased between 2014 and 2015. It is the first time in 10 years that any states have seen a decline in obesity rates, the CDC said, however, the number of obese adults went up in Kansas and Kentucky.

The South had the highest prevalence of obesity, 31.2 percent, followed by the Midwest, 30.7 percent, the Northeast, 26.4 percent, and the West, 25.2 percent.

The US had the greatest number of obese people in the world, but in 2014 China replaced it. According to a study in the April issue of the Lancet, China is home to 43,200,000 obese men and 46,400,000 obese women, accounting for 16.3 percent and 12.4 percent of obese men and women around the world.

Pamela Bryant, a health communications specialist at the CDC, told Mashable that the goal of the agency's maps is to "empower" individuals and policymakers to take steps to prevent obesity, such as improving access to healthier, fresher foods.

People who are obese, compared to those with a normal or healthy weight, are at increased risk for many serious diseases and health conditions, including: high blood pressure, heart disease, stroke, type 2 diabetes and certain types of cancer, according to the CDC. The estimated annual heath care costs of obesity-related illnesses in the US is $190.2 billion or nearly 21 percent of annual medical spending, according to the Journal of Health Economics.

The Atlanta-based agency based the maps on data collected in hundreds of thousands of telephone interviews with adults from 2013 to 2015, asking people their height and weight to calculate their body mass index (BMI). BMI is a person's weight in kilograms divided by the square of his height in meters. The CDC defines obesity as having a BMI of 30 or higher.

BMI is criticized by some doctors and researchers who say that a person considered overweight or obese might be perfectly healthy because BMI can't distinguish between fat and muscle, and that even thin adults may still have unhealthy levels of fat that don't register on the scale.