Are there persons who are obese, but metabolically healthy?

The aim of this article was to review the evidence for a metabolically norm al subset of the obese and its implications for clinical and research work. The methods included literature review and correspondence with authors. Si nce 1947, when Vague described a relation between distribution of body fat and the risk factors for cardiovascular disease, much evidence has suggeste d that early onset of the obesity, hyperplasia of normal adipocytes, and no rmal quantities of visceral abdominal fat may be associated with a favorabl e 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 fa ctor 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 met abolic syndrome in the Bruneck epidemiologic study, a subgroup of obese ind ividuals with a normal metabolic response was evident. In a current study b y Brochu et al of an obese metabolically normal subgroup of postmenopausal women, visceral abdominal fat estimated by computed tomography (CT) scan an d age of onset were significant variables. The obese, metabolically normal subgroup (OBMN) must be taken into consideration in both clinical and resea rch work. Persons with OBMN and their parents may be wrongly blamed because of the obesity. Attempts at weight loss may be counterproductive. The crit eria for selection of obese research subjects may favor inclusion of an OBM N subset, which may invalidate statistical analysis. Findings suggesting th e OBMN subset include family members with uncomplicated obesity, early onse t of the obesity, fasting plasma insulin within normal range, and normal di stribution of the excess fat. Hormonal, genetic studies, and prospective st udies will help to clarify the significance and underlying mechanisms of th is subset. Copyright (C) 2001 by W.B. Saunders Company.