Obese Could Soon Outnumber Underweight Populations Worldwide

A new study suggests that within a decade, nearly a fifth of the world's population will be obese. David Gray/REUTERS

Most people know obesity is on the rise, but many don't realize just how dire the situation has become. A new study published in The Lancet sounds the alarm on planet Earth's expanding waistline. The report, the largest to date of its kind, involved 19.2 million men and women age 18 and older. The data comes from 1,698 population-based studies, accounting for 186 countries, or 99 percent of the world's population. Based on analysis of body mass indexes (BMI) across the populations, the researchers found that by 2025, approximately a fifth of the world's population will be obese. The current average BMI for men and women is just over 24; a BMI of 25 to 29 meets the criteria for overweight, while a BMI of 30 to 39 is categorized as obese.

Unsurprising to some, the U.K. and U.S. will continue to top the list of fattest countries. Approximately 40 percent of adults in the U.K. will be obese within the next decade. By comparison, 43 percent of U.S. women and 45 percent of U.S. men are predicted to be obese in 2025.

But other findings were more surprising. The analysis determined that the island nations of Polynesia and Micronesia currently have the highest average BMI in the world. In Samoa, the average BMI tips 34.8 for women and 32.2 for men.

In the past four decades, the number of obese people worldwide has been steadily on the rise. In 1975, there were some 105 million people who met the criteria for obesity, compared with 641 million in 2014. In that time period, the proportion of obese men rose from 3.2 percent to 10.8 percent, while the proportion of obese women increased from 6.4 percent to 10.8 percent. In the same time period, the number of underweight people declined for both men (13.8 percent to 8.8 percent) and women (14.6 percent to 9.7 percent) worldwide.

"We have shown that some high-income and middle-income regions are now facing an epidemic of severe obesity," the researchers write in their study. "Even antihypertensive drugs, statins, and glucose lowering drugs will not be able to fully address the hazards of such high BMI levels, and bariatric surgery might be the most effective intervention for weight loss and disease prevention and remission.However, long-term health outcomes of bariatric surgery are largely unknown and it is not accessible to most people in low-income and middle-income countries because of financial and health system barriers."

While these figures are certainly cause for concern, the researchers say low body weight is still a significant health problem in the poorest nations. For example, nearly a quarter of people living in South Asia are underweight. Timor-Leste, Ethiopia and Eritrea are nations with the lowest BMI. Low body weight also comes with a host of health challenges, including health complications for pregnant women and newborn and higher mortality rates from respiratory illnesses and tuberculosis.

In an accompanying editorial, George Davey Smith, a professor from the MRC integrative epidemiology unit at the School of Social and Community Medicine in Bristol, U.K., said global public health officials have the unique challenge of simultaneously developing interventions that address obesity and malnourishment problem at the same time.

"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.