Obesity—defined by a body-mass index (BMI) greater than 30kg/m2—is increasing in all countries, but rates vary widely between countries. In Japan and China, only 1 in 20 adult women is obese, compared to 1 in 10 in The Netherlands, 1 in 4 in the UK and Australia, 1 in 3 in the USA, and a staggering 7 in 10 in Tonga. The first paper in The Lancet Obesity Series looks at the global drivers of the epidemic, and is written by Professor Boyd Swinburn and Dr Gary Sacks, WHO Collaborating Centre for Obesity, Deakin University, Melbourne, Australia, and colleagues.
In high-income countries, the obesity epidemic seems to have begun in the 1970s and 80s, coinciding with a steady rise in the apparent food consumption per capita. Prior to this, during the first half of the 20th century, although people were beginning to use cars more and doing less physical jobs compared with the earlier 20th century, there was a matching decrease in apparent food consumption per capita that prevented a rise in obesity.
Obesity is now sweeping through low-income and middle-income countries, impeding their development and leaving many countries with a double burden of obesity-related chronic disease in some people and undernutrition in others. In high-income countries, both sexes and all ages are affected, but obesity is more prevalent in poorer people, while in lower income nations it first appears in middle-aged adults, especially women, from wealthy urban environments before spreading more broadly. Despite great success in some countries regarding the control of tobacco use, high blood pressure, and heart disease, the quest for effective obesity strategies is ongoing. The authors say: "No country can act as a public health exemplar for reduction of obesity and type 2 diabetes."
Worldwide, around 1.5 billion adults are overweight and a further 0.5 billion are obese, with 170 million children classified as overweight or obese. Obesity takes up between 2% and 6% of health-care costs in many countries, and has overtaken tobacco as the largest preventable cause of disease in some regions, such as the USA and the state of Western Australia. But, encouragingly, reports are emerging from countries such as Australia, Sweden, France, and elsewhere that obesity rates in children are leveling off or falling. The authors highlight that most countries have inadequate systems in place to monitor population weight and nutrition, which the authors say is surprising considering the magnitude of the problem.
Increased supply of cheap, tasty, energy-dense food, improved food distribution and marketing, and the strong economic forces driving consumption and growth are the key drivers of the obesity epidemic. The built environment also has an impact, in that it can blunt the effects of the drivers: as such, the Netherlands, with its intrinsic active-transport (cycling) culture, is having a slower rise in obesity prevalence than the highly car-use-intensive USA. Epigenetic factors (environmental factors that affect gene expression) are a key area of current research that may shed light on the high variability in obesity rates between individuals. While it might seem evident that individual choices are a key driver of whether someone becomes overweight, the authors point out that people have to negotiate the complexity of their environment and the choices it poses, and many of these decisions are subconscious and outside individual awareness.
The authors believe that the most effective interventions for reversing the obesogenic drivers will almost all be policy-led—mainly government policy (eg, shifting agricultural polices to incorporate health outcomes, banning unhealthy food marketing to children, healthy public sector food service policies) but some could be food industry policies (eg, moving product formulation towards healthier compositions, self-regulation of marketing to children). Policy-led solutions that apply to environments and affect the whole population have several strengths compared with health education and promotion programmes. They tend to be sustainable, affect the whole population (including those who are difficult to reach), become systemic (affecting default behaviours), and reverse some of the environmental drivers. However, the degree of political difficulty for implementation of policy and regulatory interventions is typically much higher than that for programme-based and education-based interventions. This is due partly to continuing lobbying against possible future regulation by the powerful food industry, as well as the public's own reluctance to let go of things they are used to (such as car access, cheap parking, and access to tasty but unhealthy foods). The authors also argue that, even though there are many benefits to current government policies that promote economic growth and free trade, they are contributing to the global crises of overconsumption (including obesity and climate change). They argue that a new framework is needed that promotes prosperity in a broadly defined way, including economic, social, health, and environmental aspects.
While conversion of national obesity action plans to date has been generally poor, the authors point to positive signs for the future. These include the UK's cross government strategy for obesity, marketing restrictions, and improving school food; and also the US White House Task Force on Childhood Obesity, championed by US First Lady Michelle Obama. But the authors add that, as UN Member States gather in September for the first ever UN High-Level Meeting on non-communicable diseases (NCDs), "the inexorable global rise of obesity will be the toughest challenge that they face."
Professor Boyd Swinburn, WHO Collaborating Centre for Obesity Prevention, Deakin University, Melbourne, Australia. T) +61 407 539 941 E) boyd.swinburn@deakin.edu.au
Dr Gary Sacks, WHO Collaborating Centre for Obesity Prevention, Deakin University, Melbourne, Australia. T) +61 403 491 205 E) gary.sacks@deakin.edu.au
Journal
The Lancet