Diets are increasingly important in a world of economic growth and rising incomes. And two concerns, in particular, are emerging: the effect of diet on health; and the demands made by changing diets on agriculture. The impact is most marked in the developing world, where we now see both the fastest acceleration in over-consumption and the greatest continuing toll of under-consumption. The over-consumption of food, coupled with lives that are increasingly sedentary, is producing large numbers of people who are overweight and obese – primarily in highincome countries, but also in emerging middle-income countries. Indeed, the world has seen an explosion in overweight and obesity in the past 30 years. Globally the percentage of adults who were overweight or obese grew from 23% in 1980 to 34% in 2008, with the vast majority of this increase seen in the developing world. Here, the numbers of people affected more than tripled, from around 250 million people in 1980 to 904 million in 2008. By contrast, the number of people who were overweight or obese in high-income countries increased 1.7 times over the same period. The evidence is well-established: obesity, together with excessive consumption of fat and salt, is linked to the rising global incidence of non-communicable diseases including some cancers, diabetes, heart disease and strokes. What has changed is that the majority of people who are overweight or obese today can be found in the developing, rather than the developed, world. At the same time, under-consumption of dietary energy, protein and micronutrients is still a problem for hundreds of millions of people.