Abdominal adipose tissue distribution and metabolic risk

It is now established that waist circumference remains a significant predictor of disease and metabolic risk independent of obesity measured by body mass index. These observations are reinforced by a large body of evidence implicating abdominal obesity measured by imaging modalities in the pathogenesis of numerous metabolic risk factors. However, the extent to which abdominal subcutaneous or visceral adipose tissue (AT) independently contribute to the established association between abdominal obesity and metabolic risk remains a subject of considerable research. Discrepancies in the literature may be partially explained by methodological issues, as currently there is no accepted definition for either visceral or abdominal subcutaneous AT. Accordingly, there is confusion concerning how best to measure these depots in metabolic and descriptive studies. Further, despite numerous studies linking abdominal AT depots with metabolic risk factors, the underlying mechanisms remain unclear. The primary purpose of this review is to examine the independent contribution of visceral and abdominal subcutaneous AT to the aetiology of obesity-related health risk. We begin by considering specific methodological issues with respect to the current classification of abdominal AT as measured by imaging methods. When necessary, we present original data to reinforce important concepts not suitably addressed in the literature. We conclude with a consideration of proposed mechanisms that may link abdominal adiposity and metabolic risk.