Are there persons who are obese, but metabolically healthy?

The aim of this article was to review the evidence for a metabolically normal subset of the obese and its implications for clinical and research work. The methods included literature review and correspondence with authors. Since 1947, when Vague described a relation between distribution of body fat and the risk factors for cardiovascular disease, much evidence has suggested that early onset of the obesity, hyperplasia of normal adipocytes, and normal quantities of visceral abdominal fat may be associated with a favorable metabolic response in obese subjects. Analyses in 1973 by Keyes and later by Reuben Andres in 1980 suggested that obesity for some was not a risk factor and might even be an asset. Recently, in the study by Bonora et al of the relation between insulin resistance and the 4 main disorders of the metabolic syndrome in the Bruneck epidemiologic study, a subgroup of obese individuals with a normal metabolic response was evident. In a current study by Brochu et al of an obese metabolically normal subgroup of postmenopausal women, visceral abdominal fat estimated by computed tomography (CT) scan and age of onset were significant variables. The obese, metabolically normal subgroup (OBMN) must be taken into consideration in both clinical and research work. Persons with OBMN and their parents may be wrongly blamed because of the obesity. Attempts at weight loss may be counterproductive. The criteria for selection of obese research subjects may favor inclusion of an OBMN subset, which may invalidate statistical analysis. Findings suggesting the OBMN subset include family members with uncomplicated obesity, early onset of the obesity, fasting plasma insulin within normal range, and normal distribution of the excess fat. Hormonal, genetic studies, and prospective studies will help to clarify the significance and underlying mechanisms of this subset.