Obesity Now More Common Than Underweight Worldwide

Marcia Frellick

April 02, 2016

Global obesity numbers have shot up from 105 million people in 1975 to 641 million in 2014, according to the most comprehensive body mass index (BMI) trend analysis to date.

Researchers estimate that the age-corrected proportion of men who were obese climbed from 3.2% to 10.8% in that time and the rate among women more than doubled, going from 6.4% to 14.9%. During the same 40-year period, the proportion of men who were underweight globally fell from 13.8% to 8.8% and among women it declined from 14.6% to 9.7%.

Analyzing data from 186 countries, researchers report, in an article published in the April 2 issue of the Lancet, that if current trends continue, 18% of men and 21% of women worldwide will be obese by 2025, and more than 6% of men and 9% of women will be severely obese (35 kg/m² or greater).

"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," senior author Majid Ezzati, PhD, from the School of Public Health at Imperial College London in the United Kingdom, said in a press statement.

"If present trends continue, not only will the world not meet the [World Health Organization] 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."

Weight Extremes Included for First Time

This is the first analysis of its kind to include the rates of severely obese and morbidly obese (40 kg/m² or higher) as well as a population that is often overshadowed by alarming weight-gain reports — those classified as underweight (less than 18.5 kg/m²).

Underweight numbers were highest in South Asia in 2014 at 23.4% (95% CI, 17.8%–29.2%) in men and 24% (95% CI, 18.9%–29.3%) in women. Underweight prevalence also stood at more than 12% in women and more than 15% in men in Central and East Africa in 2014, despite some reductions over the 4 decades.

More than a fifth of men in Afghanistan, India, Bangladesh, Timor-Leste, Eritrea, and Ethiopia and a quarter or more of women in Bangladesh and India are underweight, the study found. Timor-Leste reported the lowest age-standardized BMI for women, at 20.8 kg/m², and Ethiopia reported the lowest for men, at 20.1 kg/m².

Almost half of the world's underweight men (46.2%) and women (41.6%) live in India, the study found.

Addressing underweight will take advances in food security for poor countries, Dr Ezzati said. Programs would need to identify the poor and provide social assistance.

"An example is the so-called conditional cash transfers, in which the poor receive additional income/food assistance on the condition that they also attend health clinics, etc, so the assistance and the condition are both health focused," he told Medscape Medical News. "The food part should emphasize healthier foods — unprocessed grains/legumes and sources of protein and vegetables and fruits and avoiding processed foods."

In a commentary accompanying the study, George Davey Smith, MD, DSc, of the MRC Integrative Epidemiology Unit, School of Social and Community Medicine, in Bristol, United Kingdom, writes that "far fewer people globally are escaping being underweight than are becoming obese."

Underweight is associated with increased risk of morbidity, mortality, and adverse pregnancy outcomes and obesity with substantial risk of many noncommunicable diseases.

Dr Smith points out that in rich countries, the poor are more likely to be obese than those better off. But in many countries, it's the other way around. In those countries, particularly those in South Asia and Central and East Africa, "the poor remain thin to an extent that compromises health and economic productivity." Poverty-related low BMI can affect offspring for generations.

By focusing heavily on reducing obesity, resources are diverted in poor countries to a problem experienced more by the wealthy.

Countries Varied Widely

For the current study, Dr Ezzati and colleagues analyzed 1698 population-based studies, including 19.2 million people, that had measured height and weight in adults aged 18 years and older and had used a consistent protocol, then used a statistical model to estimate mean BMI and sort prevalences of BMI categories for all countries and years.

Countries varied widely. For instance, women in Singapore, Switzerland, Japan, the Czech Republic, Belgium, and France had almost no increase in average BMI (less than 0.2 kg/m² per decade) over 40 years.

Dr Ezzati said that this may be because these are places where people are more likely to eat fresh and unprocessed foods and to eat in moderation. "The former at least should be transferable through the right pricing and regulatory policies," he said.

Polynesia and Micronesia had the highest average BMI in the world. More than 38% of men and over half of women are obese there.

The study finds that almost 20% of the world's obese adults (118 million) live in six high-income countries—Australia, Canada, Ireland, New Zealand, the United Kingdom, and the United States. More than a quarter (27.1% or 50 million) of the world's severely obese people also live in these countries. More than one in four severely obese men (27.8%) and 18.3% of severely obese women in the world live in the United States.

Dr Ezzati said current efforts to reduce BMI are not working and that bariatric surgery "might be the most effective intervention for weight loss and disease prevention and remission." However, he acknowledges the long-term effects of the surgery are not well established and it's not a realistic solution in low- and middle-income countries.

He said although the global obesity targets currently look unattainable, they need to remain intact. "Ambitious goals have a role in creating action and showing the work that is needed," he said.

Funding for the study came from the Wellcome Trust, Grand Challenges Canada. Dr Ezzati has no relevant financial relationships. Disclosures for the coauthors are listed in the article.

Lancet. 2016;387:1377-1378, 1349-11350. Abstract, Editorial

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