The research, which was led by scientists from Imperial College London, involved the World Health Organization and over 700 researchers across the globe, incorporated measurements of weight and height from nearly 20 million adults in most of the world’s countries. The research team has also created interactive maps and other visuals - available here - that show the data for each country, and how they compare to each other.
The study, published in the journal The Lancet, calculated and compared BMI among adult men and women from 1975 to 2014. BMI is a measure of a person’s weight for their height, and indicates whether their weight is healthy. The data revealed that in four decades global obesity among men has tripled - from 3.2% in 1975 to 10.8%. Obesity among women meanwhile has more than doubled, from 6.4 % in 1975 to 14.9% in 2014.
This translates as 266 million obese men and 375 million obese women in the world in 2014. It also means the world’s population has become heavier by around 1.5kg in each subsequent decade since 1975. In addition, 2.3% of the world’s men, and 5% of the world’s women are now classed as severely obese, which is defined as having a BMI of over 35 kg/m2. This places an individual at significantly increased risk of conditions such as diabetes, heart disease and cancer.
Analysis of the findings showed more obese men and women now live in China and the USA than in any other country. However the USA still has the highest number of severely obese men and women in the world. The team predicted if these global trends continue, by 2025 18% of the world’s men and 21% of women will be obese. Furthermore, the probability of reaching the World Health Organization global obesity target (which aims for no rise in obesity above 2010 levels by 2025) will be close to zero.
Professor Majid Ezzati, the senior author of the study from the School of Public Health at Imperial, said: “The number of people across the globe whose weight poses a serious threat to their health is greater than ever before. And this epidemic of severe obesity is too extensive to be tackled with medications such as blood pressure lowering drugs or diabetes treatments alone, or with a few extra bike lanes. We need coordinated global initiatives – such as looking at the price of healthy food compared to unhealthy food, or taxing high sugar and highly processed foods - to tackle this crisis.”
The team also examined the number of people who are underweight in different countries. The results revealed levels have decreased from 14% to 9% in men, and 15% to 10% in women. The percentage of underweight individuals was nonetheless still quite high in countries such as India and Bangladesh, where nearly a quarter of adults are underweight.
Professor Ezzati added: “Our research has shown that over 40 years we have transitioned from a world in which underweight prevalence was more than double that of obesity, to one in which more people are obese than underweight. Although it is reassuring that the number of underweight individuals has decreased over the last four decades, global obesity has reached crisis point.
“We hope these findings create an imperative to shift responsibility from the individual to Governments, and to develop and implement policies to address obesity. For instance, unless we make healthy food options like fresh fruits and vegetables affordable for everyone, and increase the price of unhealthy processed foods, the situation is unlikely to change.”
The findings also showed that:
Japanese men and women had the lowest BMI in the high-income world. Average BMI was higher in English-speaking high-income countries than in non-English speaking high-income countries, with American men and women having the highest BMI of any high-income country.
The lowest BMIs in Europe were among Swiss women and Bosnian men. Men in the UK had the 10th highest BMI in Europe and women the 3rd highest in Europe. Globally, the UK ranked with the 42nd highest BMI for men and 67th highest for women.
The country with the highest average BMI was American Samoa (average BMI of 35 kg/m2 for women and 32 kg/m2 for men), where the average individual is classed as obese.
Morbid obesity, where a person’s weight interferes with basic physical functions such as breathing and walking, now affects around 1 % of men in the world, and 2% of women. In total, 55 million adults are morbidly obese.
The study was funded by The Wellcome Trust, and Grand Challenges Canada.