Body fat distribution and insulin resistance

Abstract

Obesity is defined as an excess accumulation of body fat associated with increased fat cell size and number. Obesity is a common and serious medical problem worldwide, especially in industrial countries, but the prevalence of obesity is also increasing in developing countries such as South Africa.1 One of the key factors accounting for this may be increased urbanisation.2 The movement of populations from rural to urban areas is associated with major changes in lifestyle, particularly the increased availability of calorie-dense foods and drinks. Although obesity is associated with social stigma in Western countries, public opinion of obesity and overweight in the Middle East and Africa is different, being associated more with health and wealth. Obesity occurs when energy intake is greater than energy expenditure. The surplus energy will be stored as fat in the adipose tissue. In the last decade there has been a plethora of data relating to the fact that adipose cells are not just a storage depot for excess calories; rather they are metabolically active tissue. Leptin, and more recently a number of additional hormones, growth factors and cytokines,3 have been reported to be secreted by adipocytes and to have paracrine as well as endocrine effects on a variety of target tissues. It is also known that the different fat depots in the body have different metabolic activities and this may relate to their differential effects on insulin sensitivity.