We now live in a world where more people are obese than underweight, new research published in The Lancet finds.
The analysis draws on more than 40 years of data on global, regional, and national trends in body mass index (BMI) in adults 18 and older.
"The world as a whole is getting heavier and it's getting heavier by about 1.5 kilograms [3.3 pounds] per decade on average for both men and women," senior study author Majid Ezzati, a professor at Imperial College London's School of Public Health, said in an interview with The Lancet.
The analysis found that the number of obese people worldwide has risen from 105 million in 1975 to 641 million in 2014. The proportion of obese men has more than tripled from 3.2 percent of the global population to 10.8 percent over that time period. For women, that number more than doubled from 6.4 percent to nearly 15 percent.
At the same time, the number of underweight individuals decreased by about a third in both men and women globally.
The authors project that if current trends persist, around a fifth of adults worldwide will be obese by 2025.
"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," Ezzati said in a statement. "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 prevent an epidemic of severe obesity, he argues that "new policies that can slow down and stop the worldwide increase in body weight must be implemented quickly and rigorously evaluated, including smart food policies and improved health care training."
However, the researchers point out that excessively low body weight remains a serious public health problem in the world's poorest nations that should not be overshadowed by the growing obesity epidemic. In south Asia, for example, almost a quarter of the population is still underweight, while in central and east Africa, 12 percent of women and 15 percent of men are underweight. The authors note that under-nutrition comes with a number of adverse effects, including health problems for pregnant women and their unborn children and a greater chance of early death.
In an accompanying editorial, George Davey Smith, a professor of clinical epidemiology at the University of Bristol, called the study findings "striking" and represent "a fatter, healthier but more unequal world."
He argues that although getting the obesity epidemic under control is an important public health goal, those affected by poverty and under-nutrition must not be forgotten.
"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 wrote.