In the last 50 years, sub-Saharan Africa has witnessed a significant increase in the prevalence of type 2 diabetes mellitus (T2DM), from <1% recorded in some countries in the 1960s to a regional prevalence of 4.3% in 2012 (compared with a current global prevalence of 6.4%). There is great variability in prevalence of T2DM among the African communities with some countries, such as Réunion, recording an average of 16% and others, such as Uganda registering <1% in rural communities. The greatest increase in prevalence has been registered among urban dwellers. The cause of the rapid increase in T2DM prevalence is not clear. However, studies in both rural and urban areas have found that physical activity is not an independent risk factor for the disease in the region. Physical activity level was found to be adequate in Africa, with 83.8% of men and 75.7% of women meeting the WHO recommendation of at least 150 min of moderate- to vigorous-intensity physical activity per week. The paper argues that the rapidly growing number of people >40 years old, increasing urbanization, adaptation of lifestyle behaviors that accompany urbanization and the interaction of these with a genetic predisposition to T2DM, are plausible reasons for the increasing prevalence of T2DM.