Elsevier

The Lancet

Volume 378, Issue 9793, 27 August–2 September 2011, Pages 804-814
The Lancet

Series
The global obesity pandemic: shaped by global drivers and local environments

https://doi.org/10.1016/S0140-6736(11)60813-1Get rights and content

Summary

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. This passive overconsumption of energy leading to obesity is a predictable outcome of market economies predicated on consumption-based growth. The global food system drivers interact with local environmental factors to create a wide variation in obesity prevalence between populations. Within populations, the interactions between environmental and individual factors, including genetic makeup, explain variability in body size between individuals. However, even with this individual variation, the epidemic has predictable patterns in subpopulations. In low-income countries, obesity mostly affects middle-aged adults (especially women) from wealthy, urban environments; whereas in high-income countries it affects both sexes and all ages, but is disproportionately greater in disadvantaged groups. Unlike other major causes of preventable death and disability, such as tobacco use, injuries, and infectious diseases, there are no exemplar populations in which the obesity epidemic has been reversed by public health measures. This absence increases the urgency for evidence-creating policy action, with a priority on reduction of the supply-side drivers.

Introduction

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

  • 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.

  • 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.

  • Adult obesity continues to increase almost universally, but in some childhood and adolescent populations the epidemic seems to be flattening or even decreasing.

  • Present systems for monitoring population weight and nutrition are inadequate in almost all countries.

  • 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.

  • 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.

Section snippets

The global rise in obesity prevalence

The rise of the obesity epidemic seemed to begin almost concurrently in most high-income countries in the 1970s and 1980s;6 since then, most middle-income and many low-income countries have joined the global surge in obesity prevalence in adults and children.7, 8, 9 By 2008, an estimated 1·46 billion adults globally were overweight (body-mass index [BMI] >25 kg/m2) and 502 million adults were obese (BMI >30 kg/m2).9 Furthermore, an estimated 170 million children (aged <18 years) globally were

Broad economic effects on obesity

The most obvious environmental precondition for a population to develop obesity is sufficient wealth. The relation between GDP and mean BMI is positive and linear up to a GDP of about US$5000 per person per year; at greater GDP, the relation with GDP and BMI is almost flat.29 A degree of economic prosperity is thus an enabler for obesity, but the level of prosperity does not have to be high for obesity to manifest; in some low-income countries, such as Pacific Island nations, obesity prevalence

Drivers of the obesity epidemic

We define a driver of the global obesity epidemic as an environmental factor that has changed substantially during the past 40 years (coinciding with the upswing of the epidemic), is global in nature (affecting almost all countries with enabling economic conditions), and is rapidly transmissible (in view of the near simultaneous nature of the epidemic across countries). Some environmental determinants of obesity, such as the built environment, can have important effects on behaviours;53

Other environmental and individual effects

The existing environments within a country (eg, the built environment, transport systems, active recreation opportunities, cuisines and food culture, and culture around body size) can greatly moderate or modulate the effects of the global obesity drivers on population BMI (figure 4). These effects can be powerful and help to explain much of the differences in obesity prevalence between populations. They clearly hold opportunities for interventions to make environments less obesogenic.

Approaches to address the obesity epidemic

Approaches to address the obesity epidemic are broadly categorised within figure 4, with a detailed discussion of solutions presented in the report by Gortmaker and colleagues75 in this Series.

The effects on population trajectories of obesity prevalence are likely to fundamentally differ between an intervention aimed at motivating behavioural changes (eg, health promotion programmes, social marketing, education) and policy interventions (in this context, meaning enforceable actions such as laws

Implications

In this report, we have provided an overview of the global obesity epidemic, describing the size and nature of the problem, discussing its drivers, and mapping out key contributing factors. We draw attention to the food system, operating through the energy intake side of the energy balance equation, as the dominant driver of the rise in obesity, although many other environmental and individual factors modulate the effect of the drivers on obesity prevalence in populations and obesity presence

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