AUDIO:In a study at Washington University School of Medicine in St. Louis, obese people were asked to gain additional weight to see how the added pounds affected their metabolic profiles.... view more

Credit: Washington University BioMed Radio

New research demonstrates that obesity does not always go hand in hand with metabolic changes in the body that can lead to diabetes, heart disease and stroke.

In a study at Washington University School of Medicine in St. Louis, researchers found that a subset of obese people do not have common metabolic abnormalities associated with obesity, such as insulin resistance, abnormal blood lipids (high triglycerides and low HDL cholesterol), high blood pressure and excess liver fat.

In addition, obese people who didn't have these metabolic problems when the study began did not develop them even after they gained more weight.

The findings are published Jan. 2 in The Journal of Clinical Investigation.

The study involved 20 obese participants who were asked to gain about 15 pounds over several months to determine how the extra pounds affected their metabolic functions.

"Our goal was to have research participants consume 1,000 extra calories every day until each gained 6 percent of his or her body weight," said first author Elisa Fabbrini, MD, PhD, assistant professor of medicine. "This was not easy to do. It is just as difficult to get people to gain weight as it is to get them to lose weight."

All of the subjects gained weight by eating at fast-food restaurants, under the supervision of a dietitian. The researchers chose fast-food chain restaurants that provide rigorously regulated portion sizes and nutritional information.

Before and after weight gain, the researchers carefully evaluated each study subject's body composition, insulin sensitivity and ability to regulate blood sugar, liver fat and other measures of metabolic health.

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Not all obese people develop metabolic problems linked to excess weight