Fat chance: How much obesity is costing us

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Our expanding waistlines are costing the global economy almost as much to deal with as smoking and military conflict, according to a new report by the McKinsey Global Institute.

The annual global bill for obesity for lost productivity and treating conditions like diabetes, heart disease and certain cancers is $2 trillion. That's nearly as much as the $2.1 trillion smoking or war and conflict costs the global economy, a group of analysts at the research institute concluded.

Around 3.4 million adults die every year because they are overweight or obese, according to World Health Organization (WHO)statistics.

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Root causes

The long-term causes are well-known. Compared to a century ago, food is cheaper and more widely available in most countries – and lots of high-calorie foods are cheaper still. Technology means we are less likely to be walking a long way to work or school, and more likely to be sitting at a desk than tilling the soil.

The prevalence of childhood obesity is particularly concerning for future growth of the epidemic. In some low and middle income countries, "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," as high-fat, low-nutrient foods form an increasing part of the diet, according to WHO.

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Better healthcare also means that "carrying a few extra pounds is not as bad for one's health as it used to be," according to Eric Finkelstein and Laurie Zuckerman, in their book The Fattening of America. Despite several attempts, the pharmaceutical industry has not come up with a blockbuster pill-based treatment to help obese people lose weight, and the most effective, although drastic, treatment remains surgery.

The economic costs of obesity are particularly acute in the U.K., where "people are now living considerably longer than they did when the NHS was first established in 1948, but they are not living longer healthily," a group of MPs looking into primary care and public health warned last year.

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Weighing up the options

Portion control is one of the most cost-effective ways of limiting the economic impact of obesity, according to the McKinsey study.

However, intervening in people's lives is a difficult problem for governments: Clamping down on portion size or otherwise limiting access to high-calorie food and drinks can be seen as violating the right of individuals. An example of such a measure back-firing can be seen in the campaign to ban super-sized sugary drinks in New York, which was defeated in the state's Court of Appeals in June.

The best way to contain the cost of the obesity epidemic is likely to be "a combination of top-down corporate and government interventions, together with bottom-up community-led ones", the McKinsey analysts argued.

So portion control, and changing the composition and availability of high-calorie foods could go hand-in-hand with educating parents and schoolchildren, under the plans outlined.

- By CNBC's Catherine Boyle