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The rising problem of global obesity was driven home to me recently in - of all places - Sierra Leone.

This is one of the world's poorest countries with among the highest rates of malnutrition and child mortality.

And yet, walking around a hospital ward, a doctor told me that as well as malaria, pneumonia and all the other serious health challenges, there was another emerging problem - obesity.

I don't remember seeing many overweight people but the doctor assured me there was serious concern about the potential for future weight-related health problems - cardiovascular disease, diabetes and so on.

So it was no surprise to see a raft of research papers in discussing the need for global action to tackle the obesity pandemic.

Most developing countries are facing a dual challenge - that of under and over nutrition; the former gets far more publicity because it is an immediate and often life-threatening danger.

Obesity stores up a host of health problems for the future. The calls it a "double burden" of disease and says: "It is not uncommon to find under-nutrition and obesity existing side-by-side within the same country, the same community and the same household".

The WHO says that 65% of the world's population lives in countries where overweight and obesity kills more people than underweight.

The rise in urban living, the shift away from manual labour, the increase in car use and the availability of cheap energy-dense food are among many factors behind the increase.

One of the research teams led by Professor Boyd Swinburn from Deakin University in Melbourne described the "passive overconsumption" of energy: "The simultaneous increases in obesity in almost all countries seem to be driven mainly by changes in the global food system, which is producing more processed, affordable, and effectively marketed food than ever before.

In a comment article attached to the Lancet papers, Sir David King, the UK government's former Chief Scientific Advisor recalls the influential Foresight study published in 2007:

"One of the key findings of the report was that individuals had much less choice in the matter of their weight than they would assume, and that the present epidemic of obesity is not really down to laziness or overeating but that our biology has stepped out of kilter with society."

Obesity is a global issue, which requires global solutions.

Clearly individual responsibility is key, but a call for leadership is being urged in the run-up to a on non-communicable diseases in New York next month.

"Eat less, move more" maybe the simplistic answer, but today's research suggests that the issue is far more complex requiring effort from government, industry and society.