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Worldwide, more people are now obese than underweight, study finds

According to researchers’ projections, it’s likely that at least 18 percent of men and 21 percent of women across the world will be obese in 2025.

A woman takes part in an aerobics class in Los Guidos de Desamparados, Costa Rica.
REUTERS/Juan Carlos Ulate

The number of obese people in the world is now greater than the number of people who are underweight — a startling reversal of what the situation was four decades ago, according to a new study published last week in the Lancet medical journal.

If current global obesity trends continue, the study’s authors warn, “not only will the world not meet its global obesity target, but severe obesity will also surpass underweight in women by 2025.”

Obesity is defined as a body mass index (BMI) of 30 or higher, and severe obesity as one of 35 or higher.  Having a high BMI is a major risk factor for heart disease, kidney disease, type 2 diabetes and certain cancers — some of the leading causes of death and disability in the United States and around the world.

The World Health Organization has set a goal for 2025 of no increase in global obesity beyond what the levels were in 2010.

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Right now, say the authors of the new study, the chances of meeting that goal is “virtually zero.”

According to their projections, it’s likely that at least 18 percent of men and 21 percent of women across the world will be obese in 2025, up from 11 percent of men and 15 percent of women in 2014. Furthermore, 6 percent of men and 9 percent of women will be severely obese by 2014.

Hundreds of studies

To reach those numbers, the study’s authors (an international team led by researchers at the Imperial College London), analyzed data from almost 1,700 population studies involving 19.2 million adults from 186 countries between the years 1975 and 2014. All the studies had collected objective measurements of their participants’ height and weight (needed to determine BMI), as well as information about their gender and age. 

With this pooled data, the Lancet researchers were able to estimate how BMIs had changed both in individual countries and globally over the past four decades.

They found that the mean global BMI for men and women rose by the equivalent of a weight gain of 3.3 pounds per person, per decade.

They also found that the proportion of men in the world who were obese more than tripled, from 3.2 percent in 1975 to 10.8 percent in 2014, while the proportion of obese women more than doubled, from 6.4 percent to 14.9 percent.

Starting in 2004, a greater proportion of women were obese than were underweight. The same thing happened to men in 2011.

The proportion of people who were underweight (a BMI of below 18.5) fell, but only by about a third — from 13.8 percent to 8.8 percent in men and from 14.6 percent to 9.7 percent in women. 

The researchers stress that despite these declines, malnutrition remains a major health problem in many areas of the world, especially in parts of Africa and south Asia.

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U.S. numbers

Here are some other key findings from the study, including some specific to the United States: 

  • Almost a fifth of obese people in the world (118 million) live in six high-income English-speaking countries: the U.S., Canada, the United Kingdom, Ireland and Australia. And more than a quarter (50 million) of the world’s severely obese people live in these countries.
  • Among high-income English-speaking countries, the U.S. currently has the world’s highest mean BMIs for both men and women. The U.S. is home to one in four men and one in five women in the world who are severely obese.
  • By 2025, 43 percent of women and 45 percent of men living in the U.S. will be obese, if current trends continue.
  • Other regions of the world, such as Central and South America, the Middle East, and China are rapidly catching up with the English-speaking countries. China, for example, now has more obese men and women (in actual numbers) than the U.S. China has also seen a dramatic increase in severe obesity, moving from 60th place for men and 41st place for women among the 186 countries in 1975 to second place for both genders in 2014.
  • Not every country is participating equally in the global obesity epidemic. Women living in Singapore, Japan and a few European countries, including Switzerland and France, have experienced no increase in their mean BMI during the past four decades.

Weighing the implications

A commentary that accompanies the study points out that global life expectancy has also risen since 1975, from less than 59 years to more than 75 years. “The world is getting at once fatter and healthier,” writes the commentary’s author, epidemiologist George Davey Smith of the University of Bristol.

But this seeming paradox is mostly due to the fact that our medical interventions have become more effective at treating and managing heart disease, diabetes and other illnesses associated with obesity, he says.

As Smith — and the authors of Lancet study — also point out, it’s not clear if these interventions, which are costly and require advanced healthcare delivery systems, will be able to alleviate the negative health effects of obesity on populations in low-income countries.

“Furthermore,” write the study’s authors, “we have shown that some high-income and middle-income regions are now facing an epidemic of severe obesity. Even anti-hypertensive drugs, statins, and glucose lowering drugs will not be able to fully address the hazards of such high BMI levels.”

FMI: The Lancet has made both the study and the commentary available to read in full on their website.