It shouldn't be so hard, but it is.

We're getting bigger and bigger, the U.S. Centers for Disease Control and Prevention reported Thursday. And we keep packing on the pounds despite reminders, news reports and studies saying it's not smart or healthy to be overweight.

Think of it this way. For each additional hour you spend in a car, it increases your odds of being obese by 6 percent. If you walked just two-thirds of a mile daily, it would reduce your likelihood of obesity by 4.8 percent. But 25 percent of the trips we take are one mile or less, and 75 percent of those are made by car.

In Atlanta, at the final session of the CDC's three-day National Health Promotion Conference, a report was released that contained more stunningly bad news as far as America's health is concerned. It said that, despite years of heavy public and private emphasis on weight control and public promotion of healthier lifestyles, the prevalence of obesity among American adults over 18 is still increasing at alarming rates in all states, in both genders, among all racial and ethnic groups and in every age category.

But it's not all our fault, researchers say.

"A lot of emphasis has been placed on personal responsibility," said Dr. William H. Dietz, director of the National Center for Chronic Disease Prevention and Health Promotion at the CDC.

"But you can only make healthy choices if there are healthy choices to make, and we are surrounded by things that make our life easier and high-calorie food readily accessible. We don't make healthy choices."

The report said:

• Obesity has increased among men from 15.3 percent to 24.2 percent in the past decade.

• It has increased among women from 14.9 percent to 23.5 percent.

• It has increased among whites from 14.5 percent to 22.6 percent, among blacks from 22.7 percent to 33.9 percent, and among Hispanics from 16.8 percent to 26.5 percent.

Obesity increased with age, from 17.7 percent among people aged 18-29 to 29.5 percent among those 50-59.

The report also said that 60.5 percent of the total adult population in the United States is overweight or obese, compared with 56.8 percent five years ago.

Laura Kettel Khan, deputy chief for chronic disease nutrition at the CDC, said both the overweight and obese categories are based on a measure called the body mass index, known as BMI, which is a calculation based on height and weight.

Normal weight is considered a BMI of 18.5 to 24.9, . Overweight people have a BMI of 25 to 29, she said, and those who're obese 30 and up.

The higher your number, the more likely you are to develop diseases and conditions related to weight, such as diabetes, high blood pressure, high cholesterol, heart disease, stroke and certain cancers, she said.

So why aren't Americans getting the message, and are still filling fast-food restaurants that serve unhealthy foods?

"The message isn't falling on deaf ears, but the investment in identifying solutions as well as individual strategies to combat obesity are insufficient," Kettel Khan said.

"The problem is, as a nation, and in our communities, we haven't recognized the need for a societal response. We need to dramatically change our expectations for physical activity and food choices, in schools, workplaces, places of faith."

Dietz said Atlanta is a prime example of the nation's problem.

"How easy is it for children to walk to school in Atlanta? We have engineered that out of our lives. What's hopeful about Atlanta is, people are moving back into the city," Dietz said.

Some people wonder aloud why, with so much fresh food in our stories, and so much more knowledge of how much exercise matters, Americans keep getting bigger.

"There is not really that much fruit and vegetables in the stores," Kettel Khan answered. "Access to healthy foods isn't as common as we think especially in inner city, poorer neighborhoods and rural areas."