The worldwide prevalence of obesity has nearly doubled since 1980, according to a major study on how three important heart disease risk factors have changed across the world over the last three decades. The study, published today in three papers in the Lancet, looked at all available global data to assess how body mass index, blood pressure and cholesterol changed between 1980 and 2008.
The study shows that in 2008, more than one in ten of the world's adult population was obese, with women more likely to be obese than men. An estimated 205 million men and 297 million adult women were obese - a total of more than half a billion adults worldwide.
The proportion of the world's population with high blood pressure, or uncontrolled hypertension, fell modestly between 1980 and 2008. However, because of population growth and ageing, the number of people with uncontrolled hypertension rose from 600 million in 1980 to nearly 1 billion in 2008. High-income countries achieved large reductions in uncontrolled hypertension, with the most impressive progress seen in women in Australasia and men in North America. Uncontrolled hypertension is defined as a systolic blood pressure higher than 140 mmHg or diastolic blood pressure higher than 90 mmHg.
Average levels of total blood cholesterol fell in Western countries of North America, Australasia and Europe, but increased in East and Southeast Asia and the Pacific region.
Professor Majid Ezzati, the senior author of the study from the School of Public Health at Imperial College London, said: "Our results show that overweight and obesity, high blood pressure and high cholesterol are no longer Western problems or problems of wealthy nations. Their presence has shifted towards low and middle income countries, making them global problems."
Beyond global trends, the studies reveal how different countries compare in terms of each risk factor. The results show that:
The review was carried out by an international collaboration of researchers, led by Professor Majid Ezzati from Imperial College London and co-led by Dr. Goodarz Danaei from the Harvard School of Public Health, in collaboration with The World Health Organization and a number of other institutions.
Professor Ezzati added: "It's heartening that many countries have successfully reduced blood pressure and cholesterol despite rising BMI. Improved screening and treatment probably helped to lower these risk factors in high-income countries, as did using less salt and healthier, unsaturated fats.
"The findings are an opportunity to implement policies that lead to healthier diets, especially lower salt intake, at all levels of economic development, as well as looking at how we improve detection and control through the primary healthcare system. Policies and targets for cardiovascular risk factors should get special attention at the High-level Meeting of the United Nations General Assembly on Non-Communicable Diseases in September 2011."
Dr. Goodarz Danaei, from the Harvard School of Public Health, said: "This is the first time that anyone has tried to estimate trends in these major risk factors in every country in the world. The amount of data we collected is unprecedented and vast, and allows us to draw robust conclusions."
Dr. Gretchen Stevens, from the World Health Organization, said: "Our study helps track the obesity problem in individual countries and regions. We know that changes in diet and in physical activity have contributed to the worldwide rise in obesity, but it remains unclear which policies would effectively reduce obesity. We need to identify, implement, and rigorously evaluate policy interventions aimed at reversing the trends, or limiting their harmful effects."
The work forms part of the Global Burden of Diseases, Injuries and Risk Factors Study, which is supported by the Bill and Melinda Gates Foundation. The study also received funding from the World Health Organization (WHO).
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