A major study on body mass index (BMI) evolution has found that there are now more adults in the world classified as obese than underweight.

The new study, led by scientists from Imperial College London and published in The Lancet, compared BMI among almost 20 million adult men and women from 1975 to 2014.

The researchers found obesity in men has tripled and more than doubled in women.

Lead author Prof. Majid Ezzat said it was an “epidemic of severe obesity” and urged governments to act.

The study, which pooled data from adults in 186 countries, found that the number of obese people worldwide had risen from 105 million in 1975 to 641 million in 2014.

Meanwhile, the number of underweight people had risen from 330 million to 462 million over the same period.

Global obesity rates among men went up from 3.2% in 1975 to 10.8%, while among women they rose from 6.4 % in 1975 to 14.9%.

This equates to 266 million obese men and 375 million obese women in the world in 2014, the study said.

The research also predicted that the probability of reaching the WHO’s global obesity target – which aims for no rise in obesity above 2010 levels by 2025 – would be “close to zero”.

The clinical definition of obese is a BMI – a measurement that relates weight and height – of 30kg/m2.

Prof. Majid Ezzati said: “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 team also examined the number of people who are underweight, and over the same time period the study suggested the rates had fallen from 14% to 9% in men, and 15% to 10% in women.

Other statistics from the study include:

• More obese men and women now live in China and the USA than in any other country

• China has the largest number of obese people in the world with 43.2 million men and 46.4 million women
• The US has 41.7 million obese men and 46.1 million obese women
• Almost a fifth of the world’s obese adults – 118 million – live in only six high-income English-speaking countries – Australia, Canada, Republic of Ireland, New Zealand, UK, and the US
• By 2025, the UK is projected to have the highest levels of obese women in Europe (38%), followed by Republic of Ireland (37%) and Malta (34%)
• Being underweight remains a significant health problem in countries such as India and Bangladesh