A study of nearly 100 years of data on what Americans eat shows a huge increase in processed carbohydrates, especially corn syrup, and a large drop in the amount of fibre from whole grains, fruits and vegetables.
It parallels a spike in the number of cases of type-2 diabetes, caused by the body's increasing inability to metabolise sugars properly.
"We are seeing this big jump in the number of calories," that people are eating, Dr Lee Gross, a family physician at the Inter-Medic Medical Group in North Port, Florida, who led the study, said on Thursday.
"We tried to break down where are these calories coming from? We have heard everyone debating is it because of fat, is it because of carbohydrate and it is not really clear," Gross added.
"This shows the increase in the past 20 years is almost exclusively carbohydrates and certainly corn syrup consumption has increased dramatically."
Gross said he was not "picking on the corn syrup industry," but added: "It is hard to ignore the fact that 20% of our carbohydrates are coming from corn syrup – 10% of
our total calories."
Writing in the American Journal of Clinical Nutrition, Gross and colleagues showed that people ate about the same amount of carbohydrates a day on average - 500g - since 1909.
"We have heard everyone debating is it because of fat, is it because of carbohydrate and it is not really clear"
Dr Lee Gross,
Inter-Medic Medical Group
But instead of whole grains and vegetables, people are getting more and more of those carbs in the form of processed grains and sugars - most of all, in corn syrup.
An estimated 16 million Americans have type-2 diabetes, the sixth leading cause of death overall. And many studies have linked a high intake of refined carbohydrates and other foods with a high "glycemic index" with the development of diabetes.
But Audrae Erickson, President of the Corn Refiners Association, called the report misleading.
Diabetes rates are rising in many countries around the world that use little or no high fructose corn syrup in foods and beverages, Ericson said, adding it proved that the primary causes of diabetes are obesity, advancing age and heredity.