Obesity is a global problem, unequally distributed between and within countries. In affluent societies excess weight is more common among socially disadvantaged groups,1 but the inverse is true in low income countries (fig 1⇓).2

Obesity and its unequal distribution is a consequence of the complex system operating at global, national, and local levels, shaping how we trade, live, learn, and work. Focusing only on direct action to make people eat more healthily and be more physically active misses the heart of the problem: the underlying unequal distribution of factors that support the opportunity to be a healthy weight. Unless this oversight is addressed the obesity epidemic and its inequities will persist and possibly increase.

A change in diet towards highly refined foods and meat and dairy products containing high levels of saturated fats has been occurring globally since the middle of the 20th century. This, together with marked reductions in energy expenditure, is believed to have contributed to the rise in levels of obesity.3 Of concern in this paper are the causes of, and solutions to, these large scale changes in diet and physical activity and their unequal social distribution.