The largest ever obesity study reveals that the world’s obese population has hit 640 million meaning that more than one in ten men and one in seven women across the globe are now obese.

The research, co-authored by Professor Gareth Stratton, Head of the Research Centre in Applied Sports, Technology, Exercise and Medicine (A-STEM) at Swansea University and led by scientists from Imperial College London, involved the World Health Organisation and over 700 researchers across the globe, incorporating 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 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 per cent in 1975 to 10.8 per cent. Obesity among women meanwhile has more than doubled, from 6.4 per cent in 1975 to 14.9 per cent 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 per cent of the world’s men, and five per cent 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 per cent of the world’s men and 21 per cent 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 per cent to nine per cent in men, and 15 per cent to 10 per cent 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.’