One-Fifth of the World Will be Obese by 2025, Analysis Predicts

There are now more people in the world who are obese than underweight, according to estimates based on a pooled-analysis of population studies, and if current trends continue, “the probability of meeting the global obesity target [will be] virtually zero,” researchers say.

With high body mass index (BMI) a risk factor for multiple adverse cardiovascular outcomes, the growing presence of obesity is worrisome to healthcare practitioners, especially those who focus on prevention. The obesity epidemic has been on the minds of many in the medical community for years, but a pooled analysis conducted by the Non-Communicable Disease (NCD) Risk Factor Collaboration of 1,698 population-based studies involving 19.2 million participants paints a black and white picture of how glaring the problem is and will continue to be.

Researchers led by Mariachiara Di Cesare, PhD (Imperial College London, England), looked at BMI trends of adults living in 186 countries between 1975 and 2014. Using global models to calculate increases over time, they estimate that the number of obese people (BMI ≥ 30 kg/m²) increased from 105 to 641 million over the study period. Breaking it down by sex, the proportion of obese men tripled (3.2% to 10.8%) and the proportion of obese women more than doubled (6.4% to 14.9%) since 1975. Meanwhile, they estimated that the proportion of underweight people fell by about one-third in both men (13.8% to 8.8%) and women (14.6% to 9.7%).

In an age-corrected analysis, BMI increased from 21.7 kg/m² to 24.2 kg/m² in men and from 22.1 kg/m² to 24.4 kg/m² in women; these shifts equate to the world’s population gaining 1.5 kg during each of the past four decades. If this trend continues, investigators predict that 18% of men and 21% of women will be obese by 2025, and more than 6% of men and 9% of women will be severely obese (BMI ≥ 35 kg/m²).

Extremely low bodyweight is still an issue—especially in places like South Asia where they estimated about a quarter of the population is underweight—but the focus of public health officials has certainly shifted to obesity, says senior author Majid Ezzati, PhD (Imperial College London, England ), in a press release. “Over the past 40 years, we have changed from a world in which underweight prevalence was more than double that of obesity, to one in which more people are obese than underweight,” he said. “If present trends continue, not only will the world not meet the obesity target of halting the rise in the prevalence of obesity at its 2010 level by 2025, but more women will be severely obese than underweight by 2025.”

To stop the obesity epidemic from steamrolling through the coming decades, Ezzati recommends quickly enacting “new policies that can slow down and stop the worldwide increase in body weight . . . including smart food policies and improved health-care training.”

In an accompanying commentary, George Davey Smith (School of Social and Community Medicine, Bristol, England), said that even though readers of the study “know that the world’s population is getting heavier, . . . [the level of detail in the findings] remains striking.”

Prevention, he continued, “is proving hard—partly for physiological reasons.” Various studies have concluded conflicting results on how physical activity actually influences BMI and interventions that seem reasonable “have had little influence on the flow or content of the many ‘calls to action’ on global obesity.”

Smith describes “a fatter, healthier but more unequal world,” highlighting the disparity between the obesity epidemic in high-income countries and malnourishment in low-income ones. “A focus on obesity at the expense of recognition of the substantial remaining burden of undernutrition threatens to divert resources away from disorders that affect the poor to those that are more likely to affect the wealthier in low income countries,” he writes.

Additional highlights from the study include:

• Average BMI stayed similar over the study period (< 0.2 kg/m² per decade) in women in Singapore, Japan, Czech Republic, Belgium, France, and Switzerland.
• Island nations in Polynesia and Micronesia have the highest average BMI in the world, while Timor-Leste, Ethiopia, and Eritrea have the lowest.
• More than a fifth of men in India, Bangladesh, Timor-Leste, Afghanistan, Eritrea, and Ethiopia, and a quarter or more of women in Bangladesh and India are underweight.
• Worldwide, more than one in four severely obese men and almost one in five severely obese women live in the United States.
• In 2014, almost a fifth of the world’s obese adults (118 million) lived in only six high-income English-speaking countries—Australia, Canada, Ireland, New Zealand, UK, and USA.

• Di Cesare M, Bentham J, Stevens GA, et al. Trends in adult body-mass index in 200 countries from 1975 to 2014: a pooled analysis of 1698 population-based measurement studies with 19·2 million participants. Lancet. 2016; 387:1377-96.
• Smith GD. A fatter, healthier but more unequal world. Lancet. 2016; 387:1349-1350.

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