Non-communicable diseases (NCDs), including diabetes and other forms of glucose intolerance, hypertension, dyslipidemia, and obesity, are on the increase in developing countries. The clustering of these diseases in the same individuals is sometimes referred to as “metabolic syndrome” or “insulin resistance syndrome.” While the major cause of mortality in much of sub-Saharan Africa continues to be infectious disease, it is likely that the health transition will see NCDs, and metabolic syndrome in particular, take over this role in the next two decades. Urban dwellers show a much higher rate of these NCDs compared to rural dwellers. Our data from Tanzania as well as a variety of published studies illustrate the urban-rural difference in patterns of disease. This contrast leads to the question of whether particular lifestyle features of city dwelling predispose individuals to metabolic syndrome, or whether individuals with a genetic predisposition to metabolic syndrome self-select for migration to cities. The interaction of adaptation, modernization, stress and disease seems likely to play a role in the changes experienced by rural-to-urban migrants, with the caveat that locally specific cultural, historical and economic factors must be taken into consideration. Understanding the causes of adult ill-health in the urban environment will enhance the ability of governments to plan appropriate health policies.
