There has been a huge increase in the number of obese people worldwide over the past 40 years – 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 yesterday in The Lancet.

The age-corrected proportion of obese men has more than tripled (3.2 per cent to 10.8 per cent), and the proportion of obese women has more than doubled (6.4 per cent to 14.9 per cent) since 1975. At the same time, the proportion of underweight people fell more modestly – by around a third in both men (13.8 per cent to 8.8 per cent) and women (14.6 per cent to 9.7 per cent).

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 per cent) and women (21 per cent) worldwide will be obese, and more than 6 per cent of men and 9 per cent 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,” explains senior author Professor Majid Ezzati from the School of Public Health at Imperial College London, London, UK.

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 healthcare training.”

Media outlets yesterday picked up on the rapidly rising obesity levels in the UK. By 2025, this country is projected to have the highest levels of obese women in Europe (38 per cent), with similar trends projected in men. By comparison, 43 per cent of women and 45 per cent of men in the US are predicted to be obese by 2025.