Identification and Characterization of Metabolically Benign Obesity in Humans

Abstract

The prevalence of obesity is increasing worldwide, and this epidemic is accompanied by a high incidence of type 2 diabetes mellitus and cardiovascular disease.¹ Although overall obesity delineates an important risk factor for these diseases, it is recognized that body fat distribution additionally represents an independent determinant. For any given amount of total body fat, individuals with a selective excess of intra-abdominal (visceral) adipose tissue, estimated by an increased waist circumference, are at substantially higher risk of being insulin resistant and having a cardiovascular risk profile.^2-8 Excess visceral fat accumulation results from the inability of adipose tissue to appropriately store the excess energy. According to this hypothesis, energy is deposited as fat intra-abdominally and in ectopic depots such as the liver and the skeletal muscle, resulting in an increased risk of type 2 diabetes mellitus and cardiovascular disease. In contrast, when extra energy is directed toward the subcutaneous depots or is burned within the mitochondria in the liver and muscle, the individual, although having a positive energy balance, will be protected against the development of these diseases.⁹ Accordingly, it may be possible to identify a metabolically benign fat distribution phenotype even in the obese spectrum. Such individuals may be protected from type 2 diabetes mellitus and cardiovascular disease.