How Changing Age Structure and Urbanization Will Affect Food Security in Sub-Saharan Africa

(March 2012) Sub-Saharan Africa’s population will likely more than double by 2050 even if fertility drops steadily, from 856 million today to almost 2 billion people.1 There will be more than twice as many people to feed in a region that already faces great food security challenges. PRB’s new policy brief, “Population and Food Security: Africa’s Challenge,” examines this issue by looking at trends in population growth, fertility, and family planning in the region and makes the case that investments in women and family planning are necessary to fulfill future food needs.


Population growth, however, is not the only factor that will contribute to increased food needs in sub-Saharan Africa. Recent analysis by Barbara Boyle Torrey, former PRB Visiting Scholar, suggests that changes in age structure and urbanization will also play significant roles in the growth of food needs in the region.2


Torrey uses estimates of individual daily caloric requirements together with population projections to estimate changes in the future caloric requirements of sub-Saharan Africa’s population. Caloric requirements vary by age (children need fewer calories than adults), gender (men need more calories than women), and by activity level (sedentary, moderate, and high). The concept of caloric requirement differs from food demand, which takes into account elements other than biological requirements to remain healthy, such as food preferences, prices, and markets. Nonetheless, caloric requirements can be used to evaluate the minimum amount of food that must be produced in the future to support a healthy population.


Shifts in Age Structure and Urbanization


The number of people in the future will be the single largest determinant of future caloric requirements, but changing age structure and urbanization will also have important caloric implications. The United Nations Population Division’s population projections forecast a continuing shift in age structure in sub-Saharan Africa. As fertility declines, the percentage of the population ages 9 and older will rise from 68 percent to 81 percent in the next 40 years. Since children and adults ages 9 and older need 70 percent more calories than children ages 0 to 8, this trend will actually result in a 6 percent growth in caloric requirements independent of population growth.


A second important demographic factor that will affect caloric requirements in sub-Saharan Africa is urbanization. In her analysis, Torrey assumes that Africans living in urban areas have a moderate caloric requirement compared with those in rural areas who have a more active lifestyle and thus higher caloric requirements. Population projections predict extensive urbanization, with an increase from 33 percent of the population living in urban areas in 2000 to 60.5 percent by 2050. This urbanization trend seems to indicate that activity levels would decrease and thus fewer calories would be required to sustain the same number of people.


Biological caloric requirements, however, are only a rough tool to gauge the minimum amount of food needed and do not necessarily reflect food demand. Dietary research, in fact, indicates that people tend to demand more food than they actually require, particularly in urban areas. People living in urban areas in developing countries actually eat more food than their rural counterparts despite lower levels of activity. They also experience higher rates of obesity. This rural-to-urban dietary transition may also have significant implications for future food needs. As sub-Saharan Africa becomes more urban, the population will likely demand different types of foods, in particular more meat, which is more calorie-intensive to produce and thus will require either greater increases in local food production or a greater reliance on food imports.


“Demography is not destiny,” Torrey notes. Many factors may change the course of population trends, and other far-less-predictable factors will influence food security in coming years in sub-Saharan Africa, including infrastructure, governance, the global economy, and climate change. However, as Torrey writes, “The momentum of population growth means that demography will be a major factor in whether agricultural systems in Africa succeed or fail to feed their people in the future.”


Kristen Devlin is program assistant, International Programs, and Jason Bremner is program director, Population, Health, and Environment at the Population Reference Bureau.




  1. United Nations, World Population Prospects: The 2010 Revision (New York: UN Population Division, 2011).
  2. Barbara Boyle Torrey, “Population Dynamics and Future Food Requirements in Sub-Saharan Africa,” in The African Food System and its Interaction with Human Health and Nutrition, ed. Per Pinstrup-Andersen (Ithaca, NY: Cornell University Press, 2010).