Not all obese people develop metabolic problems linked to excess weight

Jan. 6, 2015

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 were published recently 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 .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. After the obese subjects gained weight, their metabolic profiles remained normal if they were in the normal range when the study began. But the metabolic profiles significantly worsened after weight gain in obese subjects whose metabolic profiles already were abnormal when the study got underway. (As part of the study, the researchers then helped the subjects lose the weight they had gained.)

Researchers identified key measurements that distinguished metabolically normal obese subjects from those with problems. One was the presence of fat inside the liver; those with abnormal metabolism accumulated fat in that organ. Another difference involved gene function in fat tissue. People with normal metabolism in spite of obesity expressed more genes that regulate fat production and accumulation.

Read the article at the JCI website