Waistlines Expand Worldwide

The world is getting heavier, an analysis of trends in nearly 200 countries showed.

From 1980 to 2008, the mean body mass index around the world increased by 0.4 kg/m² per decade for men and by 0.5 kg/m² per decade for women. 

In 2008, an estimated 1.46 billion adults worldwide had a BMI of 25 kg/m² or higher, including 502 million who were obese. During the study period, the age-standardized prevalence of obesity increased dramatically in both men (from 4.8% to 9.8%) and women (from 7.9% to 13.8%). 

Sonia Anand, MD, PhD, and Salim Yusuf, MD, DPhil, of McMaster University in Hamilton, Ontario, in an accompanying editorial, said the findings indicated "a tsunami of obesity that will eventually affect all regions of the world." 

But despite the growing obesity problem affecting nearly every region of the world, there were slight overall decreases in systolic blood pressure and fasting total cholesterol level, as shown in two additional reports by Ezzati's group. 

The researchers evaluated worldwide trends in all three cardiovascular risk factors -- BMI, blood pressure, and cholesterol levels -- by collecting data from published and unpublished health examination surveys and epidemiological studies from 199 countries and territories in the 21 subregions of the Global Burden of Diseases, Injuries, and Risk Factors study. 

In each of the three analyses, some countries did not have sufficient data -- 30 for the BMI study, 64 for the blood pressure study, and more than 100 for the cholesterol study.

The BMI study included 9.1 million participants 20 and older. The blood pressure and cholesterol studies were restricted to 5.4 million and 3 million participants, respectively, ages 25 and older. 

For both sexes, the rise in average BMI was greatest -- more than 2 kg/m² -- in Oceania. By 2008, the highest BMIs for both men and women were found on the 8.1-square-mile island of Nauru (33.9 kg/m² for men and 35 kg/m² for women). 

Residents of countries in sub-Saharan Africa and east, south, and southeast Asia had the lowest average BMIs. 

Among high-income countries, the U.S. had both the fastest rate of growth during the study (at 1.1 and 1.2 kg/m² per decade for men and women, respectively), and the highest average BMI in 2008 (28.5 and 28.3 kg/m² per decade, respectively). 

During the study period, mean systolic blood pressure decreased, from 130.5 to 128.1 mm Hg in men and from 127.2 to 124.4 mm Hg for women. That resulted in a decrease in the prevalence of uncontrolled hypertension, although the overall number of people with uncontrolled hypertension increased from 605 million to 978 million because of population growth and an aging population.  

Systolic blood pressure fell the most in North America (for men) and in Australasia and western Europe (for both sexes). Increases were observed in Oceania, east Africa, and south and southeast Asia for both sexes and in west Africa for women. 

The highest mean values were found in the east and west African countries (for both sexes) and in the Baltic nations (for men), with the lowest values in North America, Australasia, and the Asia-Pacific region.  

The authors noted that "mean BMI increased in most regions, indicating that systolic blood pressure trends might have been more favorable had BMI stayed at the levels recorded in 1980." 

Total cholesterol levels also saw slight overall decreases of about 0.1 mmol/L per decade for both sexes during the study -- settling at 4.64 mmol/L for men and 4.76 mmol/L for women in 2008 -- although the relatively little change was the result of two opposing trends. Total cholesterol levels fell in the high-income region of Australasia, North America, and western Europe, as well as in central and eastern Europe and central Asia, with declines about 0.2 mmol/L per decade for both sexes. In east and southeast Asia and the Pacific region, however, levels increased by 0.08 mmol/L per decade in men and 0.09 mmol/L per decade in women. 

There was little evidence of change in other regions of the world. 

But despite the trends, high-income countries in Australasia, North America, and western Europe still had the highest average total cholesterol level in 2008 -- 5.24 mmol/L for men and 5.23 mmol/L for women. The lowest cholesterol levels were found in sub-Saharan Africa -- 4.08 mmol/L for men and 4.27 mmol/L for women. 

In their editorial, Anand and Yusuf addressed the reason rising obesity rates were not accompanied with worsening of the other cardiovascular risk factors.  

"Systolic blood pressure and total cholesterol have decreased (despite increasing BMI), as have smoking rates," they wrote. "Changes in health behaviors, together with wider use of simple, low-cost, and effective therapies, seem to explain the marked fall in cardiovascular disease rates in the U.S." 

"These observations ... suggest that directly controlling blood pressure, total cholesterol, and smoking will lead to rapid and substantial reductions in cardiovascular disease rates even while obesity (and diabetes) might be increasing." The trends observed by Ezzati's group, however, provide a bleaker outlook for countries that are less well off. "Considering all risk-factor trends together, the forecast for cardiovascular disease burden in low-income and middle-income countries over the next few decades is dismal and comprises a population emergency that will cost tens of millions of preventable deaths, unless rapid and widespread actions are taken by governments and healthcare systems worldwide," they wrote.

• Explain that mean BMI increased worldwide from 1980 to 2008, to the point where an estimated 502 million people were obese in 2008.
  
  
• Note that despite the increasing prevalence of obesity, there were slight overall decreases in systolic blood pressure and fasting total cholesterol levels.

Farzadfar F, et al "National, regional, and global trends in serum total cholesterol since 1980: systematic analysis of health examination surveys and epidemiological studies with 321 country-years and 3.0 million participants" Lancet 2011; DOI: 10.1016/S0140- 6736(10)62038-7.