It’s commonly believed that obese people run an especially high risk of developing type 2 diabetes because their extra weight leads to insulin resistance, or because some of their weight is the result of unhealthy diets.

But a study by Irish researchers at University College Cork of “metabolically healthy” people indicates that inflammation, not weight, may be the major cause of diabetes among obese people.

“Metabolically healthy” is defined as people who show a lower range of what are called “inflammatory markers.” These markers, signs of chronic inflammation, are often precursors to such conditions diabetes and heart disease. They are often brought on by high blood sugar, high (bad) cholesterol, and high blood pressure.

The study looked at 2,040 people between the ages of 50 and 60. It found that 35 percent of obese members of the study group (obesity is defined as a body mass index of 35 or more) were metabolically healthy. That finding led to creation of a sub-category, “metabolically healthy obesity.”

Researchers did not indicate what they thought was the reason for some people’s ability to carry extra weight without an increase in risk for inflammatory maladies like diabetes and heart disease. It may have a genetic component, a possibility that requires more research.

In the meantime, they recommended testing obese people for inflammatory markers could prove to be an effective way of letting healthcare workers know which people to focus preventive efforts on, and which do not need the attention.

An abstract of the study is available in the Journal of Clinical Endocrinology & Metabolism at jcem.endojournals.org under the title “Does Inflammation Determine Metabolic Health Status in Obese and Nonobese Adults?”