As UN member states prepare to gather in New York in September, 2011, for the first High-Level Meeting of the UN General Assembly on non-communicable diseases (NCDs), the inexorable global rise of obesity will be the toughest challenge that they face. Many countries can serve as excellent exemplars for reduction of infectious diseases, injuries, and some of the risk factors for NCDs, such as smoking, high cholesterol, and hypertension. However, no country can act as a public health exemplar for reduction of obesity and type 2 diabetes. All countries are searching for answers about how to reverse the rising tide of adult and childhood obesity.
The 2004 WHO global strategy on diet, physical activity and health1 provides an excellent overall guide for societal action. However, with few exceptions, governments have made very slow progress in the implementation of these strategies. The food and media industries have, by contrast, moved rapidly by making various national2 and international3 pledges, including self-regulatory codes of practice. Although independent assessment of the true effect of these pledges is needed, governments also need to meet their obligations for policy action and leadership, which are described in several authoritative reports.1, 2, 3, 4, 5
The aim of The Lancet's Obesity Series is to state the case for action on obesity: what is the size and nature of the problem, what is driving its global increase, what will the future obesity burden be under a business-as-usual scenario, and what action is needed to reverse the epidemic? In this first report in the Series, we describe the obesity epidemic and explain the reasons for its concurrent rise across countries and the wide variation in obesity prevalence between countries. The interaction of these major determinants of obesity has important implications for the action needed to reverse the epidemic.
Key messages
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Changes in the global food system, including reductions in the time-cost of food, seem to be the major drivers of the rise of the global obesity epidemic during the past 3–4 decades, although substantial differences in national and local environments (especially sociocultural, economic, and transport environments) produce the wide variation in obesity prevalence recorded across populations.
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In the first half of the 20th century, increased mechanisation and motorisation were accompanied by corresponding decreases in food energy supply (indicative of consumption), thereby keeping obesity prevalence low. In many high-income countries, an energy balance flipping point seems to have occurred in the 1960s–70s, with an increasing food energy supply now pushing up energy intake and population weight.
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Adult obesity continues to increase almost universally, but in some childhood and adolescent populations the epidemic seems to be flattening or even decreasing.
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Present systems for monitoring population weight and nutrition are inadequate in almost all countries.
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Obesity is the result of people responding normally to the obesogenic environments they find themselves in. Support for individuals to counteract obesogenic environments will continue to be important, but the priority should be for policies to reverse the obesogenic nature of these environments.
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Governments have largely abdicated the responsibility for addressing obesity to individuals, the private sector, and non-governmental organisations, yet the obesity epidemic will not be reversed without government leadership, regulation, and investment in programmes, monitoring, and research.