Obesity has become not only a national health threat, but also a major public health challenge in the U.S. More than one-third of American adults and 17% of the nation's youth are obese, according to the Centers for Disease Control and Prevention. The CDC defines an "obese" adult as having a body mass index (BMI) equal to or greater than 30.

BMI is calculated as the weight in kilograms divided by height in meters squared, rounded to one decimal place.

Obesity-related conditions, such as heart disease, stroke, type 2 diabetes and certain types of cancer, are the leading causes of death in the U.S. In 2010, 12 states had obesity rates of 30% or more. As Americans become bigger, some businesses are struggling to deal with the expanding waistlines. The popular "Harry Potter and the Forbidden Journey" attraction at Universal Studios in Florida cannot accommodate all Harry Potter fans. Specifically, those weighing more than 265 lbs. are too heavy for the seats and therefore are excluded from the ride. An obese customer of White Castle sued the hamburger chain in 2011 when he could no longer fit in its booths.

David Kirchhoff, the president and CEO of Weight Watchers, joined The Daily Ticker to discuss America's obesity problem -- a problem he says could cost the government billions of dollars every year.

"We'll spend $200 billion this year treating diabetes, which is significantly driven by obesity," Kirchhoff tells Aaron Task at the Milken Institute Global Conference. "Twenty-five million Americans are diabetic, and there are another 78 million Americans who are pre-diabetic. We have an entire generation of people who are going to be less well as a result of lifestyle."

One recent health study found that the percentage of Medicare beneficiaries who were obese rose from 21% in 1997 to 29% in 2006. A report on the CDC web site concluded that medical costs associated with obesity were estimated at $147 billion in 2008. Medical costs for obese people paid for by third parties were $1,429 higher than those of normal weight individuals.

Obesity can affect all ages and rungs of the social ladder, but there has been a recent spotlight on the so-called "food desert" phenomenon -- low-income urban areas are lacking in supply of fresh vegetables and fruits. Michelle Obama has publicly drawn attention to the issue as part of her "Let's Move!" nationwide effort to improve the health and nutrition of children.

Weight Watchers helps millions of people around the world lose weight, and Kirchhoff says one of the first steps to losing those extra pounds begins with a new approach to eating. "We were trained to survive and hold onto our food source," he says. Processed foods -- cookies, chips, crackers, etc — have become too readily available to eat, he says, which encourages constant and mindless snacking.

"In the past 30 years, there has been such a radical change in the food environment," he says. Processed foods also cost less than whole grains and fresh produce, causing many families on a tight budget to choose less-healthy options. The maxim to "eat your vegetables" applies more than ever today. "We tend not to eat enough vegetables and fruits as a society," Kirchhoff says.