The age-corrected proportion of obese men has more than tripled, and the proportion of obese women has more than doubled since 1975. At the same time, the proportion of underweight people fell more modestly--by around a third in both men and women.
In the past 40 years, there has been a startling increase in the number of obese people worldwide--rising from 105 million in 1975 to 641 million in 2014, according to the most comprehensive analysis of trends in body mass index (BMI) to date, published in The Lancet.
The age-corrected proportion of obese men has more than tripled (3.2% to 10.8%), and the proportion of obese women has more than doubled (6.4% to 14.9%) since 1975. At the same time, the proportion of underweight people fell more modestly--by around a third in both men (13.8% to 8.8%) and women (14.6% to 9.7%).
Over the past four decades, the average age-corrected BMI increased from 21.7kg/m² to 24.2 kg/m² in men and from 22.1kg/m² to 24.4 kg/m² in women, equivalent to the world's population becoming on average 1.5kg heavier each decade. If the rate of obesity continues at this pace, by 2025 roughly a fifth of men (18%) and women (21%) worldwide will be obese, and more than 6% of men and 9% of women will be severely obese (35 kg/m² or greater).
However, excessively low body weight remains a serious public health issue in the world's poorest regions, and the authors warn that global trends in rising obesity should not overshadow the continuing underweight problem in these poor nations. For example, in south Asia almost a quarter of the population are still underweight, and in central and east Africa levels of underweight still remain higher than 12% in women and 15% in men.
"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," explains senior author Professor Majid Ezzati from the School of Public Health at Imperial College London, London, UK. "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."
He adds, "To avoid an epidemic of severe obesity, 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."