In the public mind, sub-Saharan Africa is a region plagued by war, famine and disease. Now it faces a new threat — obesity. It is not a problem widely associated with a continent where millions live on less than a dollar a day. But growing rates of obesity are posing a significant risk to the health of the next generation.

With a population that has passed one billion, Africa is starting to experience the ills of the developed world, driven by changing diets, urbanisation and increasingly sedentary lives, according to research published in The Lancet. The reasons for the steep rise in obesity among some of the world’s poorest nations is hotly debated. One theory is that the global increase is a legacy of evolution. People from Africa, Asia and Polynesia are particularly prone to obesity because they are more likely to have inherited the genes that encourage fat storage.