Worldwide, 1 in 3 adults is overweight, and 1 in 9 is obese, according to a study in The Lancet on Feb. 12 that draws on an unprecedented volume of international data spanning the period from 1980 to 2008. These statistics bode ill for human health, experts say, triggering potentially catastrophic levels of chronic diseases, including Type 2 diabetes, cardiovascular diseases and cancers.
The study, led by Majid Ezzati, formerly an associate professor of international health at the Harvard School of Public Health (HSPH) and now chair in Global Environmental Health at Imperial College London, paints a stark picture: Obesity affects half a billion adults worldwide, a doubling of prevalence within 28 years. International monitoring groups such as the World Health Organization estimate that each year 3 million deaths can be attributed to obesity-related illnesses, including heart disease and stroke, musculoskeletal disorders, Type 2 diabetes and cancers of the breast, endometrium, gall bladder, kidney, colon and esophagus. So swiftly have waistlines expanded that some experts argue that, in high-income nations, gains in pounds could threaten gains in life expectancy.
Study researchers—including Goodarz Danaei, a research fellow in epidemiology at HSPH, and an international team of clinicians and researchers known as the Global Burden of Metabolic Risk Factors of Chronic Diseases Collaborating Group—showed that mean body mass index (BMI) increased in most countries, and in high-, middle- and low-income nations alike. Among high-income countries, the United States had the largest rise, more than 1 kg/m2/decade, as well as some of the higher mean BMIs for both men and women, greater than 28 kg/m2. (A standard measure of body weight, BMI is based on height and weight and is expressed as kilograms per square meter of height.)
The health implications of these findings are dire, said JoAnn Manson, the Elizabeth Fay Brigham Professor of Women’s Health and chief of the Division of Preventive Medicine at Brigham and Women’s Hospital.
“The numbers are staggering and portend an enormous burden of future disease,” Manson said. “Many countries that are now experiencing a higher prevalence of obesity have populations that, because of genetic determinants, recently adopted Westernized lifestyles, or even in utero factors, are particularly vulnerable to developing Type 2 diabetes because of weight gain. Asian populations, people in India, Native Americans, Hispanics, Pacific Islanders—each group is susceptible to developing diabetes with more moderate levels of overweight than other populations are.”
In Manson’s view, the data should give policymakers the incentives and tools they need to bring about change. “It’s important that health ministers and government officials have these numbers,” she said. “Social and cultural factors contribute to the prevalence of overweight and obesity, so whether nations choose to encourage physical activity through the built environment or to work with the food industry to address nutrition, they need reliable statistics to help them make decisions about their use of resources.”
The study was designed to provide that information. “We measured the performance of individual countries so that nations might use the data for benchmarking,” Ezzati said. “Studying what the best-performing countries are doing could inform other countries of ways they might work to decrease obesity in their populations. We can’t simply address this issue by reversing things; we’re not going to get rid of cars or supermarkets. We need to look for imaginative and effective policies and programs that are doable in the current social context.”
The researchers swept together published and unpublished information from health examination surveys and epidemiological studies involving 9.1 million people in 199 countries and territories. Using a statistical method known as a Bayesian hierarchical model, they estimated BMI by age, country and year. Overweight signifies at least 25 kg/m2, obese 30 kg/m2 and above.
To understand how those numbers translate to what the scale says, consider that if you are five feet, five inches tall and weigh 140 pounds, your BMI is 23. Add 10 pounds, and you are overweight; another 30 pounds, and you are obese.
In the United States, the impulse is to finger a bad guy. Ban super-sized burgers. Tax sugary soft drinks. Advise mom and dad to put junior on a diet. Eat less, exercise more.
But the problem defies easy solutions. Companion studies by the research team on serum cholesterol and blood pressure changes in the course of the same 28 years show that pharmaceutical interventions and nutritional policies have led to improvements in some parts of the world. In high-income regions such as the United States, Australia and Europe, serum cholesterol levels, although still high, actually declined among both men and women. In East and Southeast Asia and the Pacific, however, levels increased.
Blood pressure measures showed similar regional and national variations. Although levels for men and women in North America, Australasia, Asia-Pacific and Western Europe declined, blood pressure levels rose for men and women in East Africa, South and Southeast Asia, and the island nations in the South Pacific. Despite some gains in hypertension control, population growth and aging pushed up by 62 percent the number of people diagnosed with the condition, from an average of 605 million in 1980 to 978 million in 2008.
The decline in cholesterol and hypertension in some countries together with a rise in obesity has created a “wild card” situation, noted Ezzati: Will blood pressure and cholesterol go down so much that they will offset the rise in BMI, or will they not?
“Everyone with good intentions has ideas on how to reduce obesity,” Ezzati said. “The reality is that in most of the world, those good intentions don’t seem to be working. These data provide an empirical dimension to a debate that tends to be emotional.”
For more information, students may contact Majid Ezzati, chair of Global Environmental Health at Imperial College London, at majid.ezzati@imperial.ac.uk.
The Evidence Adds Up
- Between 1980 and 2008, the percentage of obese men worldwide more than doubled, to 9.8 percent. Obesity’s prevalence in women climbed by three-fourths, to 13.8 percent.
- BMIs were highest in the island of Nauru: 33.9 for men, 35 for women. Eight other island nations in the South Pacific region known as Oceania saw steep increases.
- Of high-income countries, the United States had the highest BMIs: above 28 for both men and women. Next came New Zealand. Japan’s were lowest: about 22 for women, 24 for men.
- Some of the largest increases were in wealthy countries: the United States first, followed by New Zealand and Australia (women) and the United Kingdom and Australia (men).
- Women in Singapore, Italy, Belgium and Switzerland saw virtually no rise in BMI.
- In 1980, female BMI in several countries in sub-Saharan Africa and South and Southeast Asia was below 19; by 2008, the lowest BMIs hovered around 21.
