NEW YORK — Refined carbohydrates and certain vegetable oils are to blame for the surging levels of obesity in the United States, said Barry Sears, the creator of the Zone diet and a popular diet author.

Dr. Sears, in an article in Experience Life magazine, said the underlying cause of obesity is not poor discipline but increased inflammation because of the combination of refined carbohydrates and elevated intake of omega-6 fatty acids in the American diet. The combination results into increased levels of a new fatty acid called arachidonic acid, he said.

“The underlying cause of the obesity crisis that is expanding waistlines and health care costs in America is far more complex than we are led to believe,” Dr. Sears said.

He said high levels of refined carbohydrates activate enzymes that convert omega-6 fatty acids into arachidonic acid, a building block of cellular inflammation. Sources of omega-6 fatty acids include soybean oil, sunflower seed oil and corn oil, he said.

“It is arachidonic acid that causes the cellular inflammation that leads to a ‘fat trap’ that essentially locks incoming calories that have been metabolically converted into fat in the fat cells and prevents their release to be converted into the necessary chemical energy required for metabolism and movement. The result is increased appetite and eventual overconsumption of calories to generate enough energy for daily activities.”

Dr. Sears said intake of shortenings such as soybean oil has increased markedly since the 1970s.

“A diet rich in refined carbohydrates and omega-6 fats is like adding a lighted match to a barrel of gasoline when it comes to increasing cellular inflammation,” Dr. Sears said. “Americans have been doing this for 40 years with a corresponding worsening of general health in America.”

Popularized in the 1990s, the Zone diet advocated a balance between intake of carbohydrates, protein and fat in the diet.

More recently, the diet takes a restrictive view of carbohydrates, suggesting consumption of “favorable” carbohydrates, including vegetables, lentils, beans, whole grains and fruits. The revised diet and the theories related to arachidonic acid were published by Dr. Sears in a 2010 book, “Toxic Fat.”